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Malik, Shagufta. "The behaviour of surfactants in nonaqueous media." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299582.
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Heift, Claudia. "Zusammensetzung und Funktionalität des Lecithins aus Rapssaaten für erweiterte Anwendungen im Lebensmittelbereich." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=984535756.
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Mackie, Andrew C. "Lecithin-stabilised silica dispersions in non-aqueous media." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236022.
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Wettstein, Hans-Rudolf. "Influence of plant lecithins on rumen fermentation, lipid digestion and quality of milk and body fat in cattle /." [S.l.] : [s.n.], 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13721.
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Soares, Marinalda da Silva. "Processamento de oleo de soja utilizando ultrafiltração em miscela na etapa de degomagem e na obtenção de lecitina." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254701.
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Orientadores: Lireny Aparecida Guaraldo Gonçalves, Luiz Antonio ViottoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Tradicionalmente o óleo de soja bruto é degomado por adição de água ou solução ácida. A tecnologia de membranas aplicada ao processamento de óleos vegetais tem se tornado importante, pois utiliza baixas temperaturas, não necessita de tratamento de águas residuais, retém compostos indesejáveis, além de preservar compostos minoritários importantes no óleo. Os objetivos deste trabalho foram otimizar as condições de ultrafiltração de miscela de óleo de soja bruto como alternativa à degomagem clássica, avaliar as características físico-químicas e sensoriais do óleo degomado e desodorizado em escala piloto e obter lecitina de soja através da concentração do retentado. A ultrafiltração da miscela foi realizada à 40 ºC, em unidade piloto NETZSCH utilizando duas membranas cerâmicas em alumina, pré-condicionadas, com diâmetro de poro de 0,01mm, de 19 e 37 canais. O efeito da pressão transmembrana e do teor de fósforo na alimentação foram avaliados com relação ao fluxo de permeado e retenção de fosfolipídios. A faixa de pressão transmembrana utilizada nos tratamentos foi de 0,6 a 2,0 bar, sob velocidade tangencial de 3,5 m/s. Foi estabelecido um planejamento experimental fatorial 22 completo, com 3 pontos centrais e 4 pontos axiais, para cada membrana. O teor de fósforo na alimentação não exerceu efeito considerável no percentual de retenção, entretanto teve efeito negativo sobre o fluxo de permeado nas duas membranas. Valores maiores de pressão transmembrana favoreceram o aumento de fluxo e de retenção para membrana de 19 canais. Entretanto, para membrana de 37 canais, apenas a retenção foi favorecida pelo aumento da pressão, sendo que um grande aumento da pressão (acima de 1,5 bar) para esta membrana, teria efeito negativo sobre o seu fluxo. Os premeados obtidos nos tratamentos que apresentaram melhor retenção de fosfolipídios (>98%) para as duas membranas, ou seja, valores de fósforo abaixo do nível máximo exigido pela indústria de 10 mg.kg-1, foram desodorizados em unidade piloto de desodorização com vaso de inox encamisado de 3 litros, sob vácuo de 12 mmHg, a 230ºC, por 90 minutos, utilizando nitrogênio como gás de arraste. Após determinações físico químicas que asseguraram a qualidade, os produtos obtidos foram levados à analise sensorial de aceitação ao nível de consumidor e comparados com um óleo de soja refinado comercial. Os óleos desodorizados obtidos não apresentaram diferença significativa (p £ 0,05) entre si e comparados ao óleo de soja refinado comercial para os atributos aroma e sabor. A lecitina obtida a partir da ultrafiltração dos retentados estava de acordo com os padrões do Food Chemical Codex, com 53 % de insolúveis em acetona
Abstract: Crude soybean oil is traditionally degummed by water addition or phosphoric acid. The membrane technology applied to vegetable oils processing has become important because it allows to use temperatures, reduces waste water treatment, retains undesirable products, besides preserving important minor compounds in the oil. The objectives of this work were to optimize the conditions of crude soybean oil micelle ultra filtration as an alternative to the traditional degumming, evaluate the physical-chemical and sensorial characteristics of the degummed and deodorized oil in pilot plant scale and to obtain soy lecithin through retentate concentration. The ultrafiltration was accomplished at 40o C, in a NETZSCH pilot unit utilizing two pre-conditioned ceramic in alumina membranes with 0.01 mm pore diameter of 19 and 37 channels. The feed transmembrane pressure effect and the phosphorous content were evaluated regarding to the permeate flux and retention of phospholipids. The transmembrane pressure range used in the treatments was from 0.6 to 2.0 bar under tangential velocity of 3.5m/s. A complete 22 experimental design was established with 3 central points and 4 axial points for each membrane. The phosphorous content has not carried on considerable effect in the retention, nevertheless it had a negative effect over the permeate flux in the two membranes. Greater transmembrane pressure values favor the flux and retention increase in the 19 channels membrane. However in 37 channels membranes only the retention was favored by the increasing pressure while, a great pressure increase (above 1.5 bar), presented a negative effect on the its flux. The treatments that showed better phospholipids retention (>98%) for the two membranes, phosphorous values below the maximum level of 10 mg/kg required by the industry were deodorized in a deodorization pilot unity with stainless steel jacketed reactor with 3 liters capacity, under 12 mmHg vacuum, at 230 ºC, for 1.5 hours, using nitrogen as carrier gas. After physical-chemical determinations that assured the quality, the obtained products were analyzed regarding to the sensorial acceptance at the consumer level and compared with commercial soybean refined oil. The statistical analysis have not shown significative difference (p £ 0.05) among the two desodorized oils and commercial soybean neutrative-bleached-desodorized oil for the aroma and flavor atributes. The obtained lecithin was in accordance with the standards of Food Chemical Codex, with 53% of acetone insoluble
Doutorado
Doutor em Tecnologia de Alimentos
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Fernandes, Gabriel Deschamps 1988. "Caracterização de lecitinas comerciais por espectrometria de massas ambiente com ionização sonic-spray." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256072.
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Orientador: Daniel Barrera ArellanoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Os fosfolipídios são definidos como o grupo de moléculas que contém um grupamento fosfato. Por apresentarem características anfipáticas, este grupo de moléculas se organiza naturalmente em bicamadas, originando as membranas dos seres vivos. Industrialmente são capazes de estabelecer interfaces óleo/água, possibilitando a formação e estabilização de emulsões. Este grupo de moléculas é bastante diverso quimicamente, sendo os principais componentes a fosfatidilcolina, fosfatidiletanolamina, fosfatidilserina, fosfatidilinositol, ácido fosfatídico e esfingomielina. A determinação e quantificação desses compostos é bastante laboriosa tanto nos meios industriais como acadêmicos, envolvendo, entre outras, etapas de digestão ácida e incineração. A espectrometria de massas desponta como uma técnica bastante favorável à análise de lipídios, englobando desde estudos clínicos até de biocombustíveis. Mais recentemente, as técnicas de espectrometria de massas com ionização ambiente facilitaram o acesso a este tipo de tecnologia, diminuindo os custos de implantação e principalmente de operação. A ionização ambiente por sonic-spray (EASI, easy ambient sonic-spray ionization) denota-se como uma técnica adequada à análise de lipídios, uma vez que não aplica alta voltagem e alta temperatura, prevenindo, portanto possíveis degradações destas moléculas. Este trabalho teve como objetivo, estudar a ionização de fosfolipídios (PL) e triacilgliceróis (TAG) frente à técnica EASI-MS, bem como, estudar a viabilidade técnica da caracterização de lecitinas comerciais por meio da técnica EASI-MS. Quanto à ionização dos lipídios, foi possível observar, nas condições de estudo, que dentro de uma mesma classe (PL ou TAG) a intensidade de ionização diminui com o aumento da cadeia dos ácidos graxos e aumenta com o aumento das insaturações. Para o estudo de caracterização foram utilizadas seis amostras de lecitina de soja comercial, obtidas por diferentes processos. As amostras foram diluídas em clorofórmio e submetidas à análise de EASI-MS, nos modos positivo e negativo. Nos espectros de EASI(+)-MS, os íons mais representativos foram os íons correspondentes à fosfatidilcolina e aos triacilgliceróis, enquanto que, nos espectros de EASI(-)-MS os íons mais representativos corresponderam à fosfatidiletanolamina, aos ácidos graxos livres e aos glicofosfolipídios. A técnica EASI-MS mostrou-se eficiente na caracterização das lecitinas comerciais. Sendo uma técnica rápida e que não exige preparo de amostra
Abstract: Phospholipids are defined as the group of molecules containing a phosphate grouping. As they have amphipathic characteristics, this group of molecules naturally organizes bilayer, origin the membranes of living organism and are able to establish an industrial oil / water interface, allowing the formation and stabilization of emulsions. This group of molecules is very chemically different; the main components are phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidic acid and sphingomyelin. The determination and quantification of these compounds is very laborious for the academic and industrial circles, involving, among others, several steps, like acid digestion and incineration. Mass spectrometry is emerging as a very favorable tool of lipids analysis, since clinical and biofuel studies. Recently, the techniques of ambient mass spectrometry have facilitated the access to this type of technology, reducing deployment costs and especially the operation. Easy ambient sonic-spray ionization (EASI) denotes as a suitable technique to analyze the lipids, since it does not apply high voltage and high temperature, and thereby prevent possible degradation of these molecules. This work aimed to study the ionization of phospholipids (PL) and triacylglycerols (TAG) in EASIMS technique, as well as studying the technical feasibility of the characterization of commercial lecithins by EASI-MS. On the lipid ionization, it was observed, under the conditions of the study, that within the same class (TAG or PL) the ionization intensity decreases with increasing of fatty acids chains and increases with increasing of unsaturation. For characterization studies were used six samples of commercial soy lecithin, obtained by different processes. Samples were diluted in chloroform and analyzed for EASI-MS in positive and negative ion modes. In the spectra of EASI (+)- MS, the most representing ions are corresponding to triglycerides and phosphatidylcholine, whereas in the spectra of EASI (-)-MS the most representative ions correspond to the phosphatidylethanolamine, the free fatty acids and glicophospholipidios. The EASI-MS technique was efficient in the characterization of commercial lecithins. As a fast technique and does not require sample preparation
Mestrado
Tecnologia de Alimentos
Mestre em Tecnologia de Alimentos
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Svensson, B. Martin. "Lipase catalysis in lecithin-stabilised microemulsions." Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406836.
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Beattie, Stuart Gavin. "Lecithin colesterol ACYL transferase gene transfer studies." Thesis, Royal Holloway, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409233.
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Ghazi, Samira. "Factors influencing expression of lecithin : cholesterol acyltransferase." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322763.
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Chamberlin, Richard Addison. "Light scattering studies on lecithin micellar solution." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13859.
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Viñado, Martínez Alberto. "Use of soybean lecithin in broiler chicken diets." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/667795.
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La adición de grasas es una práctica habitual en la fabricación de piensos para avicultura, ya que son fuente de energía y ácidos grasos esenciales. La disponibilidad de ingredientes con alto contenido energético se puede ver reducida a causa del aumento de población mundial y la utilización de aceites vegetales para la producción de biodiesel. Por ello, la lecitina de soja (L), un coproducto del refinado del aceite de soja (S), puede ser una fuente de energía alternativa, ya que presenta un alto contenido en fosfolípidos, triacilgliceroles, ácidos grasos libres (AGL), fósforo, colina y compuestos antioxidantes. Por todo ello, el objetivo de la tesis fue estudiar el uso potencial de L como fuente de energía para piensos de pollos de carne.
Para ello, se realizaron varios ensayos con el objetivo de estudiar el uso de L como fuente de energía en la alimentación de pollos y evaluar su influencia sobre el rendimiento productivo, digestibilidad de los ácidos grasos (AG), utilización de la energía y perfil de AG de la grasa abdominal. Una dieta base fue suplementada al 3% con S o aceite ácido (A), que fueron sustituidos por niveles crecientes (1%, 2% y 3%) de L (cruda o con alto contenido en AGL en el Capítulo Tres y Cuatro, respectivamente). En relación con la sustitución de S por L, aunque durante la fase de iniciación no se observaron efectos sobre el rendimiento productivo, los balances de digestibilidad demostraron que la incorporación de L disminuyó la digestibilidad de los AG y el contenido en energía metabolizable aparente del pienso. Sin embargo, en la fase de crecimiento-acabado, la sustitución parcial de L (hasta un 2%), no dio lugar a modificaciones en el rendimiento productivo ni la utilización de la energía y de AG. Respecto a la sustitución de A por L, tanto en fase de iniciación como en la de crecimiento-acabado, se observó que la combinación de ambos coproductos dio lugar a una mayor utilización de la energía y los nutrientes. Finalmente, el perfil de AG de la grasa abdominal estaba directamente relacionado con el perfil de AG del pienso, y no se observaron modificaciones importantes al sustituir S por L.
En el último ensayo (Capítulo Cinco) se desarrolló una prueba de campo bajo condiciones experimentales con el objetivo de estudiar, diferentes niveles de inclusión de L en sustitución de S en dietas de pollos de crecimiento y de acabado, y su efecto sobre el rendimiento productivo. Además, se estudió el efecto sobre la digestibilidad ileal de los AG, el perfil de AG de la grasa abdominal y la salud intestinal. La sustitución total del S (2% de inclusión) por L, en dietas que también contenían aceite de palma y A (3,25% y 4,5% de grasas añadidas en crecimiento y acabado, respectivamente) no modificó el rendimiento productivo, la digestibilidad ileal de los AG totales y la morfología yeyunal. Por otro lado, se observó una reducción de la digestibilidad ileal de los AG poliinsaturados y un incremento en los recuentos de Lactobacillus spp. en yeyuno; aunque, sin consecuencias significativas sobre los parámetros productivos. El perfil de AG de la grasa abdominal reflejó el perfil de AG de las grasas, sin observarse importantes modificaciones.
Como conclusiones podemos decir que L es una fuente de energía alternativa adecuada para pollos de carne en crecimiento y acabado, pudiendo sustituir S hasta un 2% sin alterar el rendimiento productivo, la utilización de energía y los AG. Además, la combinación L y A es una alternativa interesante para pollos adultos gracias a la existencia de interacciones positivas sobre la utilización de la energía y los AG.Fat addition is a common practice in feed manufacturing in order to increase the energetic density of diets and provide essential nutrients to livestock animals. The availability of conventional energetic ingredients for broiler chicken diets may be compromised by a constant growing world-wide population and the current tendency to use vegetable oils for biodiesel production. In this context, soybean lecithin (L), as a co-product obtained during soybean oil (S) refining process, may represent an economical and alternative energy source due to its high content in phospholipids, triacylglycerols, free fatty acids (FFA), phosphorus, choline and antioxidant compounds. Therefore, the global aim of the present thesis was to investigate the potential use of L, as energy source for broiler chicken diets. Several trials were performed with the aim to evaluate the inclusion of L as energy source in broiler feeding and study its influence on performance, energy utilization, fatty acid (FA) digestibility and the FA profile of the abdominal fat pad. A basal diet was supplemented at 3% with either S or acid oil (A) and increasing amounts of L (crude and high in FFA for Chapter Three and Four, respectively) were included in replacement (1%, 2% and 3%). In relation to S replacement, despite no effects were observed on performance parameters, results from the digestibility balances indicated that S replacement by L, in starter broiler chickens, lowered FA digestibility and the apparent metabolizable energy content of the diets. However, in grower-finisher broiler chickens, partial replacements up to a 2%, did not modify performance, and the utilization of energy and total FA. Regarding the replacement of A by L, in starter and grower-finisher broiler chicken diets, it was observed that blending both co-products have resulted in improvements on energy and nutrient utilizations. Finally, the FA profile of the adipose tissue was a clear reflect of the FA composition of the added fats, and S replacement by L produced slight changes on the FA profile of the abdominal fat pad. The last experiment (Chapter Five) consisted in a field trial under experimental conditions with the main objective to study, in grower and finisher broiler chicken diets, different levels of L inclusion in replacement of S and its effects on growth performance. In addition, ileal absorption of FA, FA profile of the abdominal fat pad and gut health markers were assessed. Soybean oil total replacement by L (2% of inclusion), in diets that also contained palm and A (3.25% and 4.5% of total added fats for grower and finisher diets, respectively), did not modify performance parameters, total FA ileal digestibility and jejunal morphology. On the other hand, a reduction on the digestibility of the polyunsaturated FA and an increase on Lactobacillus spp. counts at the jejunum were linked to total replacement; however, with no significant consequences on growth efficiency. Slight modifications were observed on the saturation degree of the abdominal fat pad, associated to the FA profile of the different added fats. Taking all the results into account, it was evidenced that L is a suitable energetic ingredient for grower and finisher broiler chicken diets due to it was observed that S partial replacements up to a 2% by L do not alter growth performance and the utilization of energy and FA. Besides, the blending of L and A results an interesting option, for adult broiler diets, due the existence of positive interactions on energy and FA utilization.
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Alsaab, Hashem O. "Evaluation of the Percutaneous Absorption of Chlorpromazine Hydrochloride from PLO Gels Across Porcine Ear and Human Abdominal Skin." University of Toledo Health Science Campus / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=mco1435670713.
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Low, J. K. "Protein and cell therapy for lecithin-cholesterol acyltransferase (LCAT) deficiency." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/14474/.
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Lecithin-cholesterol acyltransferase (LCAT) is an enzyme principally secreted by the liver into the circulation where it esterifies cholesterol and plays a key role in high- density lipoprotein (HDL) metabolism. In familial and acquired (liver disease) LCAT deficiency, the failure to esterify cholesterol causes many cellular and metabolic disturbances. Here, I describe the purification of recombinant LCAT and assess two approaches to treat LCAT deficiency. Human LCAT cDNA was cloned into a selectable expression vector and used to generate a stably–transfected Chinese hamster ovary (CHO) cells secreting human LCAT tagged with 6 histidine residues. Productive clones were selected, monitoring LCAT activity by a modification of a radioactive enzymic assay for plasma, and the enzyme purified from culture medium by immobilised cobalt affinity chromatography. The pure LCAT, as judged by SDS- PAGE, was used to raise monoclonal antibodies in LCAT knockout mice for future development of a sensitive immunoassay. For therapy, I evaluated injection of pure LCAT into the peritoneal cavity of LCAT knockout mice using single and repeat dose regimes. LCAT activity was measurable in plasma post-injection and the percentage of esterified cholesterol increased, while agarose gel electrophoresis confirmed a rise in HDL levels. In a second approach, I encapsulated the recombinant CHO cells in biocompatible and semipermeable alginate-polylysine microcapsules using a syringe pump extrusion method. A study in vitro showed that, after an initial lag phase, LCAT was secreted for over 90 days with the capsules remaining intact. These microencapsulated cells were implanted into peritoneal cavities of LCAT-deficient mice. LCAT activity was detected in mice plasma one week post-implantation; the relative amount of esterified cholesterol was increased and lipoprotein profile was improved. I conclude that injection of recombinant enzyme or of encapsulated LCAT-secreting cells are feasible therapies for familial and acquired LCAT deficiency.
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Lucht, Julie. "Viscosity Characterization of 20% Pluronic Lecithin Organogel at varying pHs." The University of Arizona, 2009. http://hdl.handle.net/10150/623980.
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Class of 2009 AbstractOBJECTIVES: The primary objective of this experiment was to characterize the pH stability range of 20% Pluronic lecithin organogel (PLO). We intended to determine the viscosity at varying pHs. We prepared six samples of 20% PLO. METHODS: An initial rheological reading of each sample was recorded by a dynamic stress rheometer. Each sample was titrated drop-wise with citric acid or KOH in 0.5 pH increments. When the desired pH was obtained, a 0.5 mL sample was analyzed with a dynamic stress rheometer, RS-200, using Rheos software. RESULTS: Since PLO is a non-Newtonian substance, viscosity changed relative to shear stress and we were not able to examine a correlation of pH with viscosity. Instead we inputted the data into Microsoft Excel® and plotted a shear stress versus viscosity curve for each sample to identify trends. CONCLUSIONS: We were unable to achieve our primary objective of determining the viscosity characterization of 20% PLO at varying pHs due to the non-Newtonian nature of the material. Subjectively, we determined the viscosity of 20% PLO is not substantially affected by pH. Other factors such as temperature, excess liquid, and surfactant ability may influence viscosity and need to be examined in the future.
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Taylor, Lynn Elizabeth. "Acid-base regulation during sprint exercise in horses fed lecithin." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06062008-163251/.
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Cavaco, Carolina Cavaco M. Carolina. "Structural and dynamic properties of giant polymer-like lecithin reverse micelles /." [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10897.
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Svensson, Dag. "Creating High Fat Emulsions with Mango, Rapeseed Oil and Soy Lecithin." Thesis, Linnéuniversitetet, Institutionen för naturvetenskap, NV, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-24084.
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Food inevitably plays a vital role in our lives and is of great importance to our health and wellbeing. With increasing age, it is equally important to achieve adequate nutrition to prevent and alleviate age-related diseases. One problem is that far too many older adults find it difficult to eat enough nutritious food which in the long term may lead to malnutrition. With an increasing life expectancy the older population is growing and the problem with malnutrition is of great concern. Malnutrition can be caused by many different factors which make it difficult to find a single unique solution to the problem. Oral nutritional supplementation is one approach which has proved to be useful for improving the nutritional intake. This paper examines the possibility of creating high fat fruit emulsion with mango puré, rapeseed oil and lecithin, using simple blending equipment. The puré-like products were evaluated for emulsion stability by a storage test, oil droplet size by a light microscope and light scattering device, viscosity by a viscometer, sensory properties by Flavoring profiling. Furthermore the nutritional values were calculated. Successful emulsions were created using up to 50 g/100g rapeseed oil with adequate emulsion stability without lecithin. The energy content of the highest fat emulsion was 475kcal/100g. The quantities of lecithin used in these products reduced the oil droplet size but lowered the emulsion stability perhaps by depleting the stabilizing effect of mango originated particles. The lecithin made the product more viscous, also the oily and creamy/Rich mouth-feel were perceived higher with increasing lecithin. In these products and with the quantities used the lecithin was redundant. Further development of similar products but with addition of protein and perhaps sugar, to enhance flavor, should be of high interest.
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Kotzian, Roland. "Removal of metal ions from aqueous solutions using lecithin enhanced ultrafiltration." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/15378.
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This work is concerned with an alternative method for metal ion removal from aqueous solutions - surfactant enhanced ultrafiltration. Surfactant monomers aggregate above a certain concentration, specific to the surfactant, to form micelles. Anionic surfactant micelles will attract and bind metal cations. Free metal ions and surfactant monomers pass freely through an ultrafiltration membrane, but if the micelle-metal ion complex is sufficiently large it is rejected. Research reported in this thesis has been carried out on well defined aqueous solutions containing only one type of metal ion together with the natural surfactant lecithin. Lecithin is a food grade by-product of the soybean processing industry and it was chosen because it is non-toxic, biodegradable, abundant and inexpensive. It has a high molecular weight of about 750 Daltons and forms large size micelles. The main aim was to identify the basic mechanisms which influence the permeate flux and rejection levels of the process. The project was carried out in three stages. Stage one was the characterisation of the feed solution which included the determination of the critical micelle concentration using surface tension measurements, measurement of micelle size and zeta potential using a Malvern zeta sizer and visualisation of the micelle shape using scanning electron microscopy of freeze fractured lecithin solution droplet. In the second stage filtration experiments were carried out at a wide range of lecithin concentrations, metal ion concentrations and operating conditions. The experiments were run for 5 hours, by which stage a steady state condition was reached in all cases. Permeate samples were taken after I, 3 and 5 hours. Permeate flux was monitored throughout the experiment. The following properties were monitored for the feed solution at the beginning and the end of each experiment and for all permeate samples: lecithin concentration, copper concentration, pH, conductivity. In the 3 stage Electron Dispersive Analysis by X-ray (EDAX), Scanning Electron Microscopy (SEM) and a X-ray Photoelectron Spectrum Technique (XPS) were employed to investigate any membrane feed solution interactions. The results of the 3 stages were used to identify the basic mechanisms which control the permeate flux levels and the extent of component rejection in lecithin enhanced ultrafiltration.
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Yip, Shiu Hang. "Supercritical Fluid Extraction and Chromatography of Various Lipids from Soybean Lecithin." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/35349.
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Phospholipids are commonly found in biological membranes. They have a polar head group and two ester linked fatty acids tails. Different methods such as thin layer chromatography and high performance liquid chromatography coupled with ultraviolet, refractive index, flame ionization detector, and mass spectrometry (MS) detection have long been used in the study of phospholipids. These methods were time-consuming and lacked quantitative accuracy. In this work, phosphatidylcholine, phosphatidyl-ethanolamine, phosphatidylinositol and phosphatidylserine have been studied by supercritical fluid chromatography (SFC) coupled with evaporative light scattering detection (ELSD) and mass spectrometry (MS). Four different silica-based stationary phases were studied: 2-ethylpyridine, 4-ethylpyridine, diol and conventional cyanopropyl. The influence of different mobile phase additives on the elution of phospholipids has been studied. The results have shown that isopropylamine is a better additive compared with ammonium acetate, tetrabutyl-ammonium acetate, and trifluoroacetic acid for the elution of phospholipids. All phospholipids have been eluted with baseline separation in less than 15 minutes although there is some partial overlap on the pyridine columns. The second goal for this work was fractionation of phospholipids from lecithin (a by-product from soybean) by using supercritical fluid extraction (SFE) with methanol-modified CO2. Neutral lipids were first removed from the crude sample using pure CO2. Partrial fractionation of PE and nearly pure fractionated PC were obtained by varying the modifier concentration in the extraction fluid at 460 atm and 40oC with silica gel inside the extraction vessel. A total of six components were isolated from crude soybean lecithin.Master of Science
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Corswant, Christian von. "Lecithin-based microemulsions for pharmaceutical use phase behavior and solution structure /." Lund : Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/68945035.html.
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Sperber, Galia. "Attempts to generate atheroprotective lecithin-cholesterol acyltransferase (LCAT) phenotypes by chimeraplasty." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1446120/.
Full textAbstract:
Lecithin-cholesterol acyltransferase (LCAT) is a high-density lipoprotein (HDL)-associated enzyme, which is secreted mainly by the liver. By esterifying cholesterol in the surface of immature HDL, LCAT drives reverse cholesterol transport, an important process in preventing atherosclerosis. Specific point mutations in the LCAT gene, producing serine to alanine amino acid substitutions at positions 208 or 216, are reported to increase enzymatic activity up to 14 times. Here, I attempt to create these mutations using a new technology, termed chimeraplasty targeted gene repair in situ using synthetic RNA-DNA oligonucleotides (chimeraplasts). First, I demonstrated that the Ser208Ala and Ser216Ala mutations do increase LCAT specific activity by comparing recombinant Ghinese hamster ovary (CHO) cells secreting wild-type LCAT (CHO-LCAT), LCATser2i6Aia, or LCATser208Aia+ser2i6Aia. I then targeted CHO-LCAT cells, and a human hepatoma cell line (HepG2), in vitro with chimeraplasts directed at the Ser208 and Ser216 sites. However, I was unable to create the required mymidine to guanine nucleotide substitution required using standard procedures, even by varying transfection conditions, repeat targeting, or altering chimeraplast design. I studied, therefore, chimeraplast uptake into the nucleus with various polyethylemmine (PEI)-based transfection reagents by using fluorescently-labelled oligonucleotides and a validated chimeraplast, able to mutate the apolipoprotein E (APOE) gene. I found that melittin-PEI, transferrin-PEI and galactose4-PEI were superior to linear PEI, but targeting the LCAT gene with these optimal reagents failed to produce either Ser208Ala or Ser216Ala mutations. Moreover, co-targeting cells simultaneously with LCAT and apoE chimeraplasts mutated the APOE gene, but not the LCAT gene. Finally, to investigate possible gene position or sequence effects I produced recombinant CHO cells expressing both LCAT and apoE targeting regions adjacent to each other. When these cells were co-targeted the Ser216Ala mutation was successful. I conclude that chimeraplast-directed gene mutation/ repair is a promising technique but further investigation is required to explain inconsistent results when targeting different cell lines.
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Ayres, Benjamin Robert. "Use of Soybean Lecithin in Shape Controlled Synthesis of Gold Nanoparticles." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/628.
Full textAbstract:
The work presented in this dissertation is a composite of experiments in the growth of gold nanoparticles with specific optical properties of interest. The goal is to synthesize these gold nanoparticles using soybean extract for not only shape control, but for propensity as a biocompatible delivery system. The optical properties of these nanoparticles has found great application in coloring glass during the Roman empire and, over the centuries, has grown into its own research field in applications of nanoparticulate materials. Many of the current functions include use in biological systems as biosensors and therapeutic applications, thus making biocompatibility a necessity. Current use of cetyltrimethylammonium bromide leads to rod-shaped gold nanoparticles, however, the stability of these gold nanoparticles does not endure for extended periods of time in aqueous media. In my research, two important components were found to be necessary for stable, anisotropic growth of gold nanoparticles. In the first experiments, it was found that bromide played a key role in shape control. Bromide exchange on the gold atoms led to specific packing of the growing crystals, allowing for two-dimensional growth of gold nanoparticles. It was also discerned that soybean lecithin contained ligands that blocked specific gold facets leading to prismatic gold nanoparticle growth. These gold nanoprisms give a near infrared plasmon absorption similar to that of rod-shaped gold nanoparticles. These gold nanoprisms are discovered to be extremely stable in aqueous media and remain soluble for extended periods of time, far longer than that of gold nanoparticles grown using cetyltrimethylammonium bromide. Since soy lecithin has a plethora of compounds present, it became necessary to discover which compound was responsible for the shape control of the gold nanoprisms in order to optimize the synthesis and allow for a maximum yield of the gold nanoprisms. Many of these components were identified by high performance liquid chromatography and liquid chromatography-mass spectrometry. However, re-spike of these components into growth solutions did not enhance the growth of gold nanoprisms. Upon separating the shapes of the gold nanoparticles using gel electrophoresis, addition of KCN to the separated gold nanoparticles allowed us to extract the culpable ligands for shape control. Analysis of these ligands by mass spectrometry elucidated the identity of PA and upon re-spike of the PA into a growth solution of PC95, the growth of a near-infrared plasmon absorption was seen. The stability of these gold nanoparticles was tested with and without the addition of decane thiol and it was concluded that addition of the thiol allowed for improved stability of the gold nanoparticles towards cyanide. It was determined that at a concentration of 2 μM decanethiol, spherical gold nanoparticles remained stable to cyanide at the expense of the prismatic gold nanoparticles. However, at 5 μM decanethiol, both spherical and prismatic gold nanoparticles retained stability to cyanide in aqueous conditions.
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Arnold, Gunther. "Wirkungsbeziehungen von Lecithinen und Phospholipiden in ölbasierten Systemen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-154174.
Full textAbstract:
Lecithin wird unter anderem zur Steuerung der rheologischen Eigenschaften von Lebensmittelsuspensionen wie zum Beispiel Schokolade eingesetzt. In erster Linie findet dabei Sojalecithin Verwendung, wogegen die Wirkungen von Lecithinen aus Sonnenblumen oder Raps unzureichend dokumentiert sind. Anhand von Untersuchungen an Modellsuspensionen werden Wirkungsbeziehungen von Lecithin auf mikrostruktureller Ebene beleuchtet, um Ursachen für dessen Funktionalität in ölbasierten Suspensionen abzuleiten. Darüber hinaus erfolgt ein Vergleich der Wirkung von Soja-, Raps- und Sonnenblumenlecithin auf rheologische, sensorische und morphologische Eigenschaften von Schokolade. Rheologische Untersuchungen an Zucker/Öl- und Glaskugel/Öl-Suspensionen verdeutlichen den Einfluss der Suspensionsbestandteile auf die Wirkung von Lecithin in ölbasierten Suspensionen. Sedimentationsanalysen an Zucker/Öl-Suspensionen zeigen, dass die Reduktion der rheologischen Parameter mit der Senkung des Sedimentvolumens und einer verstärkt polydispersen Sedimentation einhergeht. Glaskugel/Öl-Suspensionen bilden im Vergleich zu Zucker/Öl-Suspensionen ein deutlich kompakteres Sediment, was auf geringer ausgeprägte Interaktionen zwischen den Glaspartikeln hindeutet und durch Untersuchungen mittels Rasterkraftmikroskop bestätigt wird. Die Anreicherung des Dispersionsmediums mit Lecithin führt zur Adsorption von grenzflächenaktiven Molekülen an der fest/flüssig-Grenzfläche und reduziert die adhäsiven Kräfte zwischen Zuckeroberflächen. In Zucker/Sojaöl-Suspensionen zeigen die Phospholipide Phosphatidsäure, Phosphatidylcholin und Phosphatidylethanolamin im Vergleich zu Sojalecithin eine geringer ausgeprägte Funktionalität bei kleinen Phospholipidkonzentrationen. Soja-, Raps- und Sonnenblumenlecithine besitzen in dunkler und in milchhaltiger Schokoladenmasse lediglich hinsichtlich ihrer Wirkung auf die Fließgrenze leichte Unterschiede. Die Präparate zeigen keine verallgemeinerbaren Wirkunterschiede auf die Fettkristallmorphologie und die Textur von gelagerter dunkler und milchhaltiger Schokolade. Des Weiteren lassen sensorische Untersuchungen keine signifikant ausgeprägte Präferenz für dunkle oder milchhaltige Schokolade erkennen, wenn die Probe mit Soja-, Raps- oder Sonnenblumenlecithin versetzt wird. Die Ergebnisse zeigen, dass die Reduktion der adhäsiven Kräfte zwischen Zuckerpartikeln eine Ursache für die Senkung der rheologischen Parameter und des Sedimentvolumens von Zucker/Öl-Suspensionen darstellt. Außerdem ist zu erkennen, dass bei geringen Phospholipidkonzentrationen synergetische Effekte zwischen unterschiedlichen grenzflächenaktiven Substanzen zu einem Anstieg der Funktionalität des eingesetzten Präparates führen können. Darüber hinaus ist festzustellen, dass Soja-, Raps- und Sonnenblumenlecithin die rheologischen, sensorischen und morphologischen Eigenschaften von Schokolade in gleichem Maß beeinflussenLecithin is used in the food industry, for example to control the rheological properties of oil-based suspensions, such as chocolate. First and foremost, soybean lecithin is used, whereas the effects of possible alternatives, such as lecithin from sunflower or canola, are still insufficient documented. On the basis of model suspensions the effect of lecithin on the microstructural level will be investigated to derive causes of the functionality of the surfactant in oil-based suspensions. Additionally, a comparison is made regarding the effects of soybean lecithin, canola lecithin and sunflower lecithin on the rheological and morphological properties as well as on sensory characteristics of chocolate. Rheological studies illustrate the influence of the suspension components to the action of lecithin in oil-based suspensions. While, in sugar/oil-suspensions, lecithin reduces apparent viscosity and yield stress, the effect of the surfactant in glass sphere/oil-suspensions depends on the dispersion medium. Sedimentation analyses of sugar/oil-suspensions show that the reduction of the rheological parameters coincides with the reduction of the sediment volume and an increased polydisperse sedimentation. The sediment of glass sphere/oil-suspensions is more compact in comparison to sugar/oil-suspensions, indicating less pronounced interactions between glass spheres. Investigations using atomic force microscopy show the less pronounced interactions between glass spheres. While interactions (adhesive forces) are detectable between sugar surfaces dispersed in oil, no interactions can be determined between glass surfaces. The enrichment of the dispersion medium with lecithin results in the adsorption of the surfactants at the sugar surface and reduces the adhesive forces. In sugar/soybean oil suspensions and at low phospholipid concentrations the results indicate a less pronounced functionality of the individual phospholipids, phosphatidylcholine, phosphatidylethanolamine and phosphatidic acid in comparison to soybean lecithin. In dark chocolate and milk chocolate soybean lecithin, canola lecithin and sunflower lecithin reduces apparent viscosity at low to medium shear rate in the same way. In contrast, small differences in terms of their effect on the yield stress are observed. The lecithins do not show differences regarding their impact on fat crystal morphology and texture of stored dark chocolate and milk chocolate. Furthermore, in sensory studies, no significant preference differences were detectable in case of dark chocolate or milk chocolate containing soybean lecithin, canola lecithin or sunflower lecithin. The results show that the reduction of the adhesive forces between sugar particles causes the reduction of rheological parameters and the sediment volume of sugar/oil-suspensions. Furthermore, at low phospholipid concentrations possible synergistic effects between different surfactants can lead to an increase of the functionality of suractants. Additionally it can be concluded that soybean lecithin, canola lecithin and sunflower lecithin affect the rheological and morphological properties as well as the sensory characteristics of chocolate in equal measure
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Yao, Zemin. "Isolation of rat liver CTP: phosphocholine cytidylyltransferase and regulation of hepatic phosphatidylcholine biosynthesis." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25073.
Full textAbstract:
Two kinds of affinity chromatography, CDP-choline- and CTP-Sepharose 4B, were investigated for purification of the cytosolic CTP:phosphocholine cytidylyltransferase from rat liver. The enzyme did not show strong affinity for the CDP-choline Sepharose resin, but bound to the CTP-Sepharose column in the presence of 14 mM magnesium acetate. The combination of CTP affinity chromatography
with ion-exchange techniques provided about 70-fold purification of the cytosolic enzyme with a specific activity of about 90 units per milligram protein.
The influence of diphenylsulfone compounds on the synthesis
of phosphatidylcholine by the CDP-choline pathway was examined in
isolated rat hepatocytes and HeLa cells. The administration of
the sulfones (100 ug/ml), except dapsone, to HeLa cells inhibited
the total [methyl-³H]choline incorporation into the cells, but did not change the rate of conversion of choline to phosphatidylcholine.
The addition of the sulfones (100 ug/ml) to rat hepatocytes
did not inhibit the biosynthesis of phosphatidylcholine and choline metabolism.
The effect of vasopressin on the distribution of cytidylyl-transferase between cytosol and microsomes in rat hepatocytes was also investigated. The digitonin-mediated release of cytosolic cytidylyltransferase was reduced from the cells treated with vasopressin (5-20 nM) , while the enhanced rate of incorporation of [methyl-³H]choline into phosphatidylcholine was not observed.Medicine, Faculty of
Biochemistry and Molecular Biology, Department of
Graduate
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Castejon, Letícia Vieira. "Parâmetros de qualidade na clarificação da lecitina de soja." Universidade Federal de Uberlândia, 2015. https://repositorio.ufu.br/handle/123456789/17770.
Full textAbstract:
A lecitina de soja é um complexo de fosfolipídeos em óleo de soja, sendo denominada de
lecitina de soja comercial. Sua coloração é âmbar, apresenta alta viscosidade, cheiro e gosto
característicos. É bastante utilizada como emulsificante, possui características próprias devido
a modificações física, químicas ou de processos de obtenção. O presente trabalho teve por
objetivo avaliar fisico-quimicamente lecitinas de soja clarificadas, pela adição de peróxido de
hidrogênio a 35% (v/v), a temperatura e agitação controladas. Avaliar os aspectos qualitativos
e de coloração, para posterior aplicação em leite integral UHT e verificação das características
de pó (molhabilidade e insolubilidade). A etapa de clarificação foi planejada
experimentalmente, através de um Planejamento Composto Central, cuja lecitina de soja
comercial, sem tratamento com peróxido foi analisada quanto à reologia, apresentando
comportamento pseudoplástico a 25°C e newtoniano à 50°C. Sua composição de ácidos
graxos foi de elevado teor de insaturados conforme análise cromatográfica. A clarificação
produziu lecitinas mais claras do que a lecitina comercial e foi selecionada a lecitina
clarificada com maior valor de luminosidade (L*) para análise reológica, a qual mostrou
mesmos comportamentos reológicos da lecitina comercial, porém com ligeiros aumentos na
viscosidade aparente. Resultado das avaliações sobre a coloração foram realizadas, mostrando
os efeitos da temperatura, tempo de agitação sob rotação constante e concentrações de H2O2
(%, m/v), obtendo-se colorações mais vermelhas e amarelas, intensas e de tonalidade
tendendo ao amarelado. O ponto experimental em que se obteve maior luminosidade, cor
branca, foi a 50°C, 520 segundos de agitação e adição de 2,3% de peróxido de hidrogênio,
35% (m/v). Um modelo de cor foi elaborado para predizer quais parâmetros de cor
influenciam sobre a cor aparente, para isso foram analisados compostos carotenoides e
clorofilas, chegando-se à conclusão que outras substâncias, como substâncias marrons e
tocoferóis, se determinadas melhorariam o ajuste. Os resultados das avaliações da qualidade
oxidativa das lecitinas clarificadas, mostraram os efeitos das variáveis do planejamento sobre
as respostas de índice de saponificação, coeficiente de oxidação, índice de acidez e atividade
de água, os resultados mostraram que em condições extremas, foram mantidos bons estados
de oxidação lipídica. A aplicação da lecitina mais clarificada no leite mostrou que a cor do
leite em pó ficou mais clara. A melhor solubilidade e menor tempo de molhabilidade foram
obtidos para concentração adicionada de lecitina igual a 1,0% (m/m) sobre a massa aplicada e as micrografias dos pós mostraram que o aumento no teor de lecitina de soja deixa os
grânulos menores e o pó mais granuloso.Soy lecithin is a complex phospholipid in soybean oil, being called commercial soybean lecithin. Its color is amber, high viscosity, smell and taste characteristic. It is widely used as an emulsifier, has its own characteristics due to physical changes, chemical or production processes. This study aimed to assess physico-chemically clarified soy lecithins, by adding hydrogen peroxide to 35% (v / v), the controlled temperature and agitation. It was considered qualitative aspects and also in color, for later use in UHT whole milk and verification of powder characteristics (wettability and solubility). The clarification step is designed experimentally, using a central composite design, the commercial soybean lecithin without peroxide treatment rheology was analyzed, showing pseudoplastic behavior at 25°C and the Newtonian at 50°C, the composition of fatty acids was higher unsaturated content as chromatographic analysis. Clarification produced lighter than lecithin and commercial lecithin was clarified lecithin selected with higher brightness value (L*) to rheological analysis, which showed the same rheological behavior of commercial lecithin, but with slight increases in apparent viscosity. Reviews staining were performed, showing the effects of temperature under constant stirring rotation time and H2O2 concentration (% w/v) to give more red dyes and yellow, intense tint and tended to yellow. The experimental point was obtained in higher brightness, white color at 50°C was 520 seconds of stirring and addition of 2.3% hydrogen peroxide, 35% (w/v). A color model is designed to predict which color parameters influence on the apparent color, for that were analyzed carotenoids and chlorophyll compounds, coming to the conclusion that other substances, such as brown substances and tocopherols, if certain improve the fit. The evaluation of oxidative quality of clarified lecithins have shown the effects of the design variables on the saponification number of responses, oxidation rate, and acid value of water activity, the results showed that in axial conditions are maintained good oxidation states lipid. The application of more clarified lecithin in milk showed that the color of milk powder became clearer. The best solubility and shorter wettability were obtained for added lecithin concentration equal to 1.0% of the applied mass and the powders micrographs showed that the increase in soy lecithin content leaves the smaller beads and the most granular powder.
Tese (Doutorado)
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Holland, Janice Lee. "Lecithin containing diets for the horse: acceptance, digestibility, and effects on behavior." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/30978.
Full textAbstract:
Lecithins may improve the digestibility of high fat diets and the tractability of horses. Experiments were conducted to determine the acceptability, digestibility and effects on behavior of lecithin-containing diets. Seven young horses of light breeds were used for the studies.
The four concentrates consisted of corn, oats, beet pulp, trace mineralized salt, dried sugar cane molasses plus 10% added fat: corn oil (CO);soy lecithin-corn oil (SL\CO); soy lecithin-soybean oil (SL\SO); or soy lecithin-corn oil-soybean oil (SL\CO\SO). Half the ration was provided by chopped hay. The CO concentrate was the most palatable (P=.OOOl). The remaining three concentrates were palatable in the following order: SL\CO, SL\CO\SO, and SL\SO, with SL\CO diet preferred (P=.OOl) to SL\SO.
In the digestibility experiment, a complete mixed diet was fed containing chromic oxide as a marker. The control diet had no added fat: the others contained CO, SL\CO, or SL\SO at 10% by weight. Apparent digestibility was higher in the control diet than in the others for dry matter (P=.OOOl). Apparent digestibilities of crude protein (P=.0002) and acid detergent fiber (P=.08) decreased with any of the three fats. In contrast, apparent digestibility of ether extract was increased (P=.OOOl) in the fat containing diets.
In the activity experiments, horses on the SL\CO diet were less spontaneously active (P=.0125) than horses on the control diet. Horses on the CO and SL \SO diet also had slightly lower activity levels (P=.125). Horses fed the SL\SO diet reacted less (P=.0625) than control horses to the opening umbrella. Horses fed CO and SL\CO diets showed trends towards less reactivity (P=.125 and P=.25, respectively), compared to the control horses.
These studies support the practical feasibility of using lecithins in diets for horses. Especially interesting would be studies of interactivity with trainers and riders.Master of Science
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Cooke, Allison L. B. A. "The Molecular Interaction of Apolipoprotein A-I and Lecithin: Cholesterol Acyl Transferase." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543580636448357.
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Wilson, Judith A. "Sarcoplasmic reticulum responses to repeated sprints, conditioning and dietary lecithin in the horse." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06062008-163309/.
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Henley, Cheryl Lynn. "Ã-naphthylisothiocyanate induced cholestasis with secondary lecithin, cholesterol acyltransferase deficiency in C57BL/6 mice." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ36465.pdf.
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Hodgson, Isaac Owusu Afriyie. "Removal of lead, copper and cadmium ions from aqueous streams using lecithin enhanced microfiltration." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/12130.
Full textAbstract:
The removal of lead, copper and cadmium ions from aqueous streams using lecithin enhanced micro filtration with 0.2μm pore size tubular ceramic membranes has been investigated. Measurements of the surface tension at varying lecithin concentrations were carried out to determine the critical micelle concentration (CMC) of lecithin and the effects of lead ions, mixtures of lead and copper ions, and mixtures of lead, copper and cadmium ions in solutions on the CMC of lecithin. The zeta potential and the effects of the single and multiple metal ions on the zeta potential of lecithin were also investigated. The influence of lecithin concentrations, cross flow velocity and transmembrane pressure on the rejections and steady state permeate flux behaviours were examined. The CMC of lecithin was found to be 9 grl. An increase in metal ion concentration caused a decrease in the CMC and an increase in the zeta potential of lecithin solutions, suggesting the binding of the metal ions onto the lecithin. An increase in lecithin concentration was found to improve metal ions removal. Lecithin showed preference for the metal ions in the order Pb2+ > Cd 2+ > Cu 2+. Metal ion removal was influenced more by lecithin concentration and less by transmembrane pressure and cross flow velocity. The steady state permeate flux and rejection behaviours have been explained by microscopic phenomena and a mathematical model has been developed to predict the steady state permeate flux. The lecithin concentration that remains in the permeate was less than 9% of the feed solution. The study has shown that lecithin enhanced micro filtration is a technically suitable technique for removal of lead, copper and cadmium ions in aqueous solution.
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Bonam, Sindhu Prabha. "Preparation and Evaluation of Pluronic Lecithin Organogel Containing Ricinoleic acid for Transdermal Drug Delivery." University of Toledo Health Science Campus / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=mco1384437353.
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Weddle, Carolyn A. "Optimization of HPLC techniques for separation of oxidized phosphatidylcholines." Virtual Press, 2005. http://liblink.bsu.edu/uhtbin/catkey/1319835.
Full textAbstract:
In cellular studies of patients with lipid related disorders such as mammary cancers, leukemia, and artheroscierosis, separation of molecular species of oxidized phosphatidylcholine (PC) can be an important assistance in research or diagnosis. Goals of this project were to optimize separation of oxidized and unoxidized PC molecular species in a single HPLC chromatogram followed by in line identification of hydroperoxides. Oxidized egg PC's were produced using UV light exposure in air. Separations were performed on an Ultrasphere ODS column and an Asahipak ODPVA column using a Waters 2695 system with photodiode array. The ODPVA column routinely gave 10 times larger plate numbers. Various mobile phase mixtures (methanol, acetonitrile, water) and gradients were tested. The optimum gradient on our system is (1) 5 minutes, 47 % methanol/40 % acetonitrile/13 water in a linear gradient to (2) 17 minutes, 49 % methanol/40 % acetonitrile/11 % water to (3) 18 minutes, 29 % methanol/60 % acetonitrile/11 % water linearly to (4) 50 minutes, 31 % methanol/60 % acetonitrile/9 % water continued isocratically to 110 minutes. Oxidized hydroperoxides were detected by fluorescence using a post column reaction with diphenyl-1 pyrenylphosphine (DPPP). Both iron (III) and pyridine were tested as catalysts for this reaction.Department of Chemistry
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Simard, Gilles. "Dynamique intra-vasculaire des lipoproteines de haute densite ; role des enzymes lipolytiques." Toulouse 3, 1990. http://www.theses.fr/1990TOU35001.
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Séguret, Mace Sandrine. "Role de la lecithine cholesterol acyltransferase dans le metabolisme des lipoproteines de haute densite (hdl) : application a la therapie genique du deficit en hdl." Paris 11, 1997. http://www.theses.fr/1997PA114808.
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Davit-Spraul, Anne. "Dyslipoproteinemie du syndrome d'alagille : capacites fonctionnelles des lipoproteines de haute densite (hdl) et activite lecithine : cholesterol acyl tranferase." Paris 11, 1997. http://www.theses.fr/1997PA114839.
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Parekh, Khushboo K. "Preparation, Characterization, and In Vitro Protein Release Studies in Pharmaceutically relevant Lecithin Microemulsions." University of Toledo Health Science Campus / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=mco1300753350.
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St, Clair Caryn M. "Neonatal Respiratory Distress Syndrome as a Function of Gestational Age and the Lecithin/Sphingomyelin Ratio." [New Haven, Conn. : s.n.], 2007. http://ymtdl.med.yale.edu/theses/available/etd-08272007-123115/.
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Madenci, Dilek. "Study of the aggregation behaviour of egg yolk lecithin/bile salt mixtures by increasing the ionic strength." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4918.
Full textAbstract:
This thesis describes a study of the aggregational behaviour of egg yolk lecithin (EYL), a natural lecithin, and bile salt mixtures especially with respect to an increase of the ionic strength of the solvent. Mixtures of two amphiphiles with very different spontaneous curvature as EYL lecithin and bile salt form mixed micelles and vesicles in aqueous solution. Their properties have been well-studied under physiological conditions, i.e. 150 mM electrolyte concentration and pH 7- 8, while other conditions are still hardly explored. Upon increasing ionic strength the formed structures and the transitional pathways (micelles, coexistence of micelles and vesicles, and vesicles) change the generated structures completely from those observed under physiological conditions. We quantitatively determined these structures formed in a broad range of electrolyte concentrations with various scattering techniques, x-ray, light and neutron scattering and calorimetry. With calorimetry, phase diagrams in the EYL and bile salt concentration phase plane were determined at various ionic strength ranging from physiological salt concentration to up to 1000 mM. Additionally a new electrochemical approach using functionalised electrodes, i.e. sensitive and selective to bile salt, and thus to control the bile salt concentration in solution (concentrations below the critical micellar concentration (cmc)) was attempted, since bile salt removal or injection drives the micelle-to-vesicle or the vesicle-to-micelle transition, respectively, of the mixed aggregational system of EYL/bile salt. Although this control was not achieved within the framework of this thesis, promising results show directions for future experiments.
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GENAY, PATRICK. "Asthme professionnel du boulanger : a propos de deux cas d'allergie respiratoire a la lecithine de soja." Reims, 1992. http://www.theses.fr/1992REIMM007.
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Ayyobi, Amir Fardad. "Analysis of lecithin : cholesterol acyltransferase (LCAT) protein structure and its influence on binding to plasma lipoproteins." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0014/NQ56499.pdf.
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Wang, Guang. "Functionality of egg yolk lecithin and protein and functionality enhancement of protein by controlled enzymatic hydrolysis." [Ames, Iowa : Iowa State University], 2007.
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Kline, Kristen Alissa. "Metabolic effects of incremental exercise on Arabian horses fed diets containing corn oil and soy lecithin." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/37030.
Full textAbstract:
Feeding a fat-containing diet to the exercising horse is a facile way to increase energy density without risking the complications associated with hydrolyzable carbohydrates. Fat adaptation may also result in increases in the utilization of free fatty acids for fuel during exercise and sparing of muscle glycogen. Phosphatidylcholine, the main component of lecithins, can influence muscle contraction and improve endurance capacity during exercise. When it is combined with corn oil in a total mixed ration, soy lecithin is both highly digestible and palatable to horses. Our objectives in this study were to compare the effects of incremental exercise and isocaloric control (CON), corn oil (CO), and a soy lecithin/corn oil (LE) diets on plasma free fatty acids (FFA), cholesterol, glycerol, triglyceride (TG), lactate, and glucose. Also three different statistical models were compared for goodness of fit to the lactate curve.
Plasma lactate and glucose both increased slowly early in the incremental exercise test (IET), then increased rapidly as the work intensity increased. Both decreased during recovery. No effects of IET or diet were found for either of these variables.
Plasma TG was unchanged during exercise, but increased rapidly during recovery. Plasma FFA decreased from resting early in the IET then remained steady throughout the remainder of exercise. During recovery a rapid increase was exhibited. Plasma glycerol was constant during exercise, but increased during recovery. Plasma cholesterol did not change during exercise or recovery.
Diet affected plasma FFA. Plasma FFA were lower for the CO and LE diets than the CON diet during the IET. Plasma glycerol was lower for the CO diet than the CON diet during the IET, with the LE diet intermediate between the two. Plasma cholesterol was higher for the CO and LE diets than the CON diet during the IET.
A segmented model and an exponential model were found to have a good fit to the lactate curve. A point of inflection for a rapid increase in plasma lactate during incremental exercise was discovered. When this model was applied to diet, no differences in lactate threshold were found between the diets.
Some criteria for fat adaptation were met, namely diet affected plasma FFA, glycerol, and cholesterol. However diet did not affect plasma TG, lactate, or glucose. This indicates that the rate of fatty acid oxidation was increased following fat adaptation, but it did not affect the rate of glucose oxidation and glycolysis during exercise. A lactate threshold for the equine can be obtained using a broken line model. Further studies using this approach are needed to establish its correlation with performance.Master of Science
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Andrade, Valléria Matos. "Obtenção de gel PLO contendo rutina para aplicação transdérmica : caracterização, estabilidade e atividade antioxidante." Pós-Graduação em Ciências Farmacêuticas, 2017. http://ri.ufs.br/jspui/handle/riufs/7785.
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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPqCoordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Rutin is a flavonoid widely reported in the literature for its antioxidant properties, anti-inflammatory, vasoprotective, antithrombogen, among others. However, its low solubility in aqueous media reduces its bioavailability orally and, therefore, transdermal administration proves to be promising. Thus, the present work aimed to obtain, characterize and evaluate an activity and antioxidant activity of a gel. PLO (Pluronic Lecithin Organogel) containing rutin for transdermal administration.The analytical methodology for rutin quantification was developed and validated by high performance liquid chromatography (HPLC). Initially it was evaluated as an influence of the concentration of Polaxamer 407, obtained by the extrusion method with the aid of syringes, in front of the centrifugation test. The formulation that remained stable after the test was characterized by partical size determination, in vitro release study, in vitro skin penetration study, in vitro skin adhesion study. Also assessed for stability for 60 days at varying temperatures and at predetermined times, physico-chemical characteristics such as pH, density, viscosity and spreadability, as well as organoleptic characteristics, were evaluated. The antioxidant activity of the formulation was evaluated by the TRAP and TAR methods, comparing it with a positive control, Trolox. The results demonstrate that a formulation with higher concentration of Polaxamer is more stable and that is why it was characterized. The partical size were perfect for dermal administration. The formulation demonstrated controlled release of the drug after 24 hours, being able to permeate as deeper layers of the skin and to be absorbed into the systemic circulation, in addition to good adhesion to the skin surface. During the accelerated stability study, as formulations stored at low temperature, they underwent small variations in density, viscosity and spreadability relative to those stored at room temperature, while the pH remained stable throughout and favorable for application in skin. However, as observed variations were not sufficient to cause visual signs of instability. As for the antioxidant activity, a formulation showed greater activity in relation to the Trolox control and the free rutin, but it was not able to sustain an activity for a longer time, presenting a lower TAR value than Trolox. Thus, a chosen formulation has been shown capable of promoting a permeation of the rutin by transdermal route in a controlled manner, as well as being stable at an ambient temperature and having more significant antioxidant activity than the free rutin, and is therefore promising to administration of rutin by this route.
A rutina é um flavonoide bastante estudado devido principalmente as suas propriedades antioxidantes, anti-inflamatória, vasoprotetora e antitrombogência. No entanto, sua baixa solubilidade em meio aquoso reduz sua biodisponibilidade por via oral e, portanto, a administração por via transdérmica pode ser uma alternativa promissora. Dessa forma, o presente trabalho teve por objetivo obter, caracterizar e avaliar a estabilidade e a atividade antioxidante de um gel contendo Pluronic Lecithin Organogel (PLO) contendo rutina, para administração pela via transdérmica. A metodologia analítica para quantificação de rutina foi desenvolvida e validada por cromatografia líquida de alta eficiência (CLAE). Inicialmente foi avaliado qual a influência da concentração do Polaxamer 407, obtidos pelo método de extrusão com auxílio de seringas, frente ao teste de centrifugação. A formulação que permaneceu estável após o teste foi caracterizada através da determinação do tamanho de partícula, estudo de liberação, penetração cutânea e adesão à pele, todos in vitro. Foi também avaliada a estabilidade do produto durante 60 dias em variadas temperaturas em tempos pré-determinados, além das análises físico-químicas, como pH, densidade, viscosidade e espalhabilidade, bem como características organolépticas. A atividade antioxidante da formulação foi determinada pelos métodos TRAP e TAR, em comparação com um controle positivo, o Trolox. Os resultados demonstraram que a formulação contendo maior concentração de Polaxamer é mais estável e por isso esta foi caracterizada. O tamanho de partícula encontrado foi 4,33 μm e o sistema se mostrou homogêneo, ideal para administração cutânea. A formulação demonstrou liberação controlada do fármaco após 24 horas, sendo capaz de permear as camadas mais profundas da pele e ser absorvida para circulação sistêmica, além de boa adesão à superfície da pele. Durante o estudo de estabilidade acelerada, as formulações armazenadas em baixa e alta temperatura, sofreram pequenas variações na densidade, na viscosidade e na espalhabilidade, em relação àquelas armazenadas a temperatura ambiente, enquanto que o pH se manteve estável durante todo o tempo e favorável à sua aplicação na pele. Além disso, as variações observadas não foram suficientes para provocar alterações visuais de instabilidade. Quanto à atividade antioxidante, a formulação demonstrou maior atividade em relação ao controle Trolox e à rutina livre, porém de forma não duradoura, apresentando valor de TAR menor que o Trolox. Sendo assim, a formulação escolhida, demonstrou-se capaz de promover a permeação da rutina por via transdérmica de forma controlada, bem como estabilidade a temperatura ambiente e com atividade antioxidante significativa, sendo considerada então promissora a administração da rutina por esta via.
São Cristóvão, SE
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Crespilho, André Maciel [UNESP]. "Estudo comparativo de diferentes metodologiasde preservação do sêmen bovino para a utilização e programas de inseminação artificial em tempo-fixo(IATF)." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/105905.
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crespilho_am_dr_botffmvz.pdf: 1224891 bytes, checksum: 5f6cd3bb0ea028b0690772b9a9bf8493 (MD5)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O objetivo do estudo foi comparar a efetividade de três diluidores empregados para criopreservação e refrigeração do sêmen bovino em relação aos padrões de motilidade, integridade de membrana plasmática e acrossomal, índice de peroxidação lipídica e fertilidade nos programas de inseminação artificial em tempo-fixo (IATF). No Trabalho científico número 1 foi comparado a viabilidade e fertilidade pós-descongelação proporcionada pelos diluidores Tris-frutose (TRIS, Controle) e Botu-Bov® (BB), ambos contendo 20% de gema de ovo como fonte de lipoproteínas, frente à diluição em Botu- Bov®-Lecitina de Soja (meio BB-L) apresentando 1% de lecitina em substituição ao produto de origem animal. No Trabalho 2 foram avaliados os mesmos diluentes quando utilizados para a refrigeração do sêmen bovino por 48 horas a 5°C. Já no Trabalho número 3 foi avaliada a taxa de concepção na inseminação artificial (C/IA) proporcionada pelo sêmen bovino refrigerado por 24 horas em meio Botu-Bov® em comparação ao sêmen convencionalmente criopreservado no mesmo diluidor. Os meios TRIS e BB a base de gema de ovo foram mais efetivos na manutenção da viabilidade espermática pósdescongelação, conferindo melhores resultados de C/IA (P<0,05) em relação ao meio BBL. No entanto, quando utilizado o sêmen na forma líquida e refrigerado (Trabalho número 2) foi observada uma maior proteção contra o estresse oxidativo proporcionado pelo diluidor a base de lecitina de soja, resultando em maior probabilidade de prenhez quando comparado às amostras refrigeradas em TRIS ou BB, alcançando índice de concepção similar ao obtido com o sêmen congelado. A utilização do sêmen bovino refrigerado por 24 horas levou ao aumento da C/IA de vacas submetidas a IATF quando comparado ao sêmen congelado em meio Botu-Bov®. Conclui-se que embora a lecitina de soja represente...
The aim of this study was to compare three different extenders used for cryopreservation of bovine semen, based on the results obtained during the cooling storage and post-thaw evaluation for motility patterns, integrity of plasmatic and acrossomal membranes, lipid peroxidation rate, as well as conception rate after fixed-time artificial insemination (FTAI). In Paper.1, the efficiency of Tris-Fructose extender (TRIS, control group), Botu-Bov® extender (BB), both containing 20% of egg yolk, and Botu-Bov®-Lecithin extender (BBL), which has 1% of soy lecithin instead of egg yolk, were compared in cryopreservation of bovine semen. In Paper.2, ejaculates from different bulls were cooled to 5°C for 48 hours using the same extenders of Paper.1. In Paper.3 the fertility trial was conducted either with frozen-thawed semen or cooled semen for 24 hours in the BB extender. The egg yolk extenders, TRIS and BB, demonstrated significant differences on the viability and the fertility of frozen-thawed bovine semen when compared to BB-L (P<0.05). However, the use of lecithin instead of egg yolk on semen extender resulted in a greater protection against oxidative stress; moreover, this extender improved the conception rates, reaching the results obtained in FTAI programs with frozen-thawed semen. The use of cooled bovine semen at 5°C for 24 hours improves the conception rate of Nelore cows submitted to FTAI. Although soy lecithin is an interesting alternative source of phospholipids in the elaboration of chemically defined extenders and decrease the risk of microbiological contamination, the egg yolk semen extenders are more effective in preserving the viability and fertility of frozen-thawed bovine semen. However, there was a higher production of free radicals in cooled semen with the use of egg yolk based extenders, resulting in lower conception rates when compared to frozen-thawed... (Complete abstract click electronic access below)
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Tantipolphan, Ruedeeporn, and n/a. "Characterisation of protein-phospholipid interactions in implantable delivery systems." University of Otago. School of Pharmacy, 2007. http://adt.otago.ac.nz./public/adt-NZDU20071218.162425.
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Purpose: This thesis aimed to gain a better understanding of the effects of salts in modifying in vitro phase behaviour of lecithin and cholesterol solid implants and to obtain further information on in vitro protein release and stability.
Methods: Raman spectroscopy and partial least squares regression (PLSR) were used to investigate lecithin-cholesterol molecular interactions as a function of method of preparation. Lipid-salt interactions were studied by attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman spectroscopy using principal component analysis (PCA). In vitro release of bovine serum albumin (BSA), a model protein, from lecithin and lecithin:cholesterol implants comprising 10 and 30% NaCl and CaCl₂ were performed. Size exclusion (SE) HPLC was used for quantitative and qualitative analysis of the released BSA. On hydration, changes in phase behaviour and implant morphology were studied by ATR spectroscopy and light microscopy. SE-HPLC, ATR and fluorescence spectroscopy were used to evaluate the structure of unreleased BSA. Protein adsorption on lipid films was studied by flow through ATR spectroscopy. Increased amide II peak area upon recirculation of BSA in salt solutions over hydrated lecithin and lecithin:cholesterol films cast on ZnSe prisms was used to quantify the deposition of BSA onto the lipid surfaces.
Results: Shifts in the Raman spectra suggested the lecithin headgroup may be involved in lecithin-cholesterol interactions. Greater R� and root mean square error of cross validation in the calibration curves of physical mixing and heating (120�C) methods reflected poor mixing in these preparations. The mean absolute residue and mean Mahalanobis distance values from the physical mixing and granulation methods indicated their spectral similarity and comparable level of lecithin-cholesterol interactions. Calcium exhibited stronger affinity for phospholipids than sodium and it induced headgroup hydration and reorganisation upon binding. PCA of ATR spectra was sensitive to cholesterol addition, calcium binding and method of preparation whilst PCA of Raman spectra only differentiated the presence of cholesterol. In vitro release of BSA from implants produced from wet granulation mixtures of lecithin and lecithin:cholesterol in the absence of salt showed retention of a high monomer content and the release profiles were similar to the literature. Cholesterol increased the swelling, induced phase transformation of lecithin and, subsequently, reduced the BSA release. Salts only slightly modified the BSA release from the lecithin implants. In contrast, for lecithin:cholesterol matrices salts greatly enhanced implant swelling, induced the formation of hydrated lecithin of heterogeneous size and inhibited the in vitro BSA release. Analyses of the protein showed increased aggregation of BSA with a high retention of native structure while retained within the swollen matrices. ATR spectra suggested that salts promoted protein adsorption onto hydrated lecithin surfaces and the effects depend on salt types (NaCl > CaCl₂) and concentration (0.1 M > 1.0 M) but not on lecithin:cholesterol surfaces.
Conclusion: PLSR and PCA can be used to investigate molecular interactions in the solid lipid matrices. In lecithin:cholesterol implants, salts modified the phase behaviour of lecithin which resulted in enhanced swelling, formation of hydrated lecithin of altered morphology and inhibition of in vitro BSA release.
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Stroppa, Valter Luís Zuliani. "Influência de lecitina e PGPR no processo de microestruturação de chocolate amargo." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266882.
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Orientadores: Lireny Aparecida Guaraldo Gonçalves, Priscila EfraimDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Chocolates são produtos compostos por uma fase lipídica com predominância de manteiga de cacau, e que contem liquor, açúcar emulsificantes e eventualmente leite em pó (ou derivados lácteos) e aromas. As características físicas dos chocolates como brilho, dureza, fusão a temperaturas da boca e estabilidade térmica são conseqüências da estruturação cristalina induzida na manteiga de cacau. Os triacilgliceróis presentes na manteiga de cacau podem-se organizar em até seis formas polimórficas sendo que apenas duas são estáveis e geram produtos de melhor qualidade. A adição de emulsificantes ao chocolate visa melhorar o comportamento reológico durante o processamento diminuindo as tensões interfaciais entre a fase gordurosa e as partículas sólidas. Os emulsificantes promovem o recobrimento das partículas sólidas com a fase oleosa lubrificando as interfaces que, desta maneira, poderão servir de elementos ativos para a nucleação. Este trabalho avaliou o efeito da adição dos dois emulsificantes mais utilizados na indústria, lecitina de soja e PGPR (poliglicerol poliricinoleato), no processo de estruturação cristalina de chocolate amargo. Foram produzidos chocolates com diferentes teores de emulsificantes conforme um planejamento fatorial completo 2² rotacionado. O nível de lecitina variou de 0,08 a 0,92% e o de PGPR de 0,02 a 0,58%. Para caracterizar esta influência foram utilizadas técnicas de reometria (determinação das propriedades de escoamento), ressonância magnética nuclear (acompanhamento da cinética de cristalização), Índice de temperagem (quantificação da pré-cristalização), e ensaios de ruptura (avaliação da resistência estrutural). Os valores de viscosidade plástica de Casson do chocolate medidos a 40ºC variaram de 1,4 a 5,9 Pa.s enquanto que o limite de escoamento variou de zero a 34Pa. Os parâmetros cinéticos avaliados de isotermas de cristalização a 15ºC ajustadas ao Modelo de Avrami resultaram no expoente n variando de 2,598 a 2,956 e o parâmetro k entre 5,15.10-6 e 2,85.10-5 min-n para os diferentes teores de emulsificantes. Estes efeitos foram associados à capacidade da lecitina em aumentar o volume cristalino e ao potencial nucleador do PGPR
Abstract: Chocolates are confectionary products composed by a lipid phase based mainly on cocoa butter that contains cocoa mass, sugar, emulsifiers and eventually milk solids and aromas. Physical characteristics of chocolates like gloss, hardness, melting at mouth temperature and thermal stability result from the crystalline structuration accomplished by the fat phase. The triacylglycerols in cocoa butter can be organized in up to six different polymorphs but only two of them are stable and therefore yield better quality products. The addition of emulsifiers to chocolates intends to improve the rheological behavior during processing by the reduction of the interfacial tension between the fat phase and the solid particles. The emulsifiers promote the coating of the solid particles by an oily layer, lubricating the interfaces that then can serve as active elements for nucleation. This work examines the effects of the addition of the two most used emulsifiers in chocolate, namely soy lecithin and PGPR (polyglycerol polyricinolate) in the crystalline structuration of chocolates. Chocolates with different contents of the two emulsifiers were produced, following a 22 complete factorial rotational design. The lecithin level varied from 0.08 to 0.92% and the PRPG content from 0.02 to 0.58%. The influence of the additives was characterized by rheometry (determination of the flowing parameters), nuclear magnetic resonance (monitoring the crystallization kinetics), Temperindex (pre-crystallization level quantification), and snap test (structural resistance). The values of Casson's plastic viscosity of the chocolates, measured at 40ºC, varied from 1.4 to 5.9 Pa.s while the yield value ranged between zero to 34 Pa. The kinetic parameters evaluated from crystallization isotherms at 15ºC modeled by the Avrami equation resulted in the exponent n varying from 2.598 to 2.956 and k parameters between 5.15 10-5 min-n and 2.85 10-5 min-n when the different amount of emulsifiers were used. These effects are associated to the ability of lecithin to enlarge the crystal volume and to the nucleating potential of PGPR
Mestrado
Engenharia de Processos
Mestre em Engenharia Química
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Li, Min. "Site-directed mutagenesis of the branchpoint sequence of intron 4 of the human lecithin : cholesterol acyltransferase gene." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0019/NQ56575.pdf.
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Saint-Pierre-Chazalet, Michèle. "Structure et interactions en mono et multicouches de cyanine a longues chaines et d'amphotericine b." Paris 6, 1987. http://www.theses.fr/1987PA066208.
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Park, Yong Bok. "Studies on Hog Plasma Lecithin:cholesterol Acyltransferase: Isolation and Characterization of the Enzyme." Thesis, North Texas State University, 1987. https://digital.library.unt.edu/ark:/67531/metadc331699/.
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Lecithin:cholesterol acyltransferase (LCAT) was isolated from hog plasma and basic physicochemical properties and functionally important regions were investigated. Approximately one milligram of the enzyme was purified to apparent homogeneity with approximately a 20,000-fold increase in specific activity. In the plasma, hog LCAT was found to associate with high-density lipoproteins (HDL) probably through hydrophobic interactions with apolipoprotein A-I. HDL was the preferred lipoprotein substrate of the enzyme as its macromolecular substrate. The enzyme was found to contain 4 free sulfhydryl groups; at least one of these appeared to be essential for catalytic activity. The enzyme had a tendency to aggregate at high concentrations. More than half of the tryptophan and none of the tyrosine residues of the enzyme were shown to be exposed to the aqueous environment based on fluorescence and absorbance studies, respectively.
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Yao, Zemin. "Phosphatidylcholine biosynthesis and lipoprotein secretion in rat hepatocytes." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29220.
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Young male rats fed a choline-deficient diet for three days accumulated triacylglycerol (TG) in the liver, and had reduced very low density lipoprotein (VLDL), but not high density lipoprotein (HDL), levels in the plasma. Cultured hepatocytes obtained from these rats were used as a model system to investigate how choline deficiency affected hepatic lipogenesis, apolipoprotein synthesis and lipoprotein secretion. When the cells were cultured in a medium free of choline and methionine, the secretion of TG and phosphatidylcholine (PC) was impaired. Supplementation of choline, methionine or lysophosphatidylcholine (lysoPC) to the culture medium increased the secretion of these lipids to normal levels, and stimulated PC biosynthesis. Fractionation of the secreted lipoproteins by ultracentrifugation revealed that the reduced secretion of TG and PC from choline-deficient cells was mainly due to impaired secretion of VLDL. The secretion of HDL and lipid-free proteins (for example albumin), however, was not affected by choline and methionine deficiency. Supplementation of betaine and homocysteine also stimulated PC biosynthesis and enhanced hepatic VLDL secretion. However, supplementation of ethanolamine, N-monomethylethanol-amine or N, N-dimethylethanolamine did not correct the impaired VLDL secretion from the hepatocytes, although an active synthesis of phosphatidylmonomethyl-ethanolamine (PMME) and phosphatidyldimethylethanolamine was observed. Choline deficiency had no effect on the rate of incorporation of [³H]leucine into cellular apolipoprotein B, E and C or on the rate of disappearance of radioactivity from the labeled apolipoproteins. These results suggest that biosynthesis of PC is specifically required for hepatic VLDL (but not HDL) secretion, and any one of the three synthetic pathways, the CDP-choline pathway, methylation of phospha-tidylethanolamine (PE) or reacylation of lysoPC, is sufficient to provide the required PC. The total activity of cytidylyltransferase in liver was unchanged in choline deficiency. However, choline deficiency caused an abnormal distribution of cytidylyltransferase activity between rat liver cytosol and microsomes (mainly endoplasmic reticulum), a decrease in the cytosolic enzyme activity and an increase in the microsomal enzyme activity. In cultured hepatocytes from the choline-deficient rat, the abnormally distributed cytidylyltransferase activity could be rapidly reversed by the addition of choline, but not lysoPC, to the culture medium. The stimulated microsomal activity of cytidylyltransferase during choline deficiency might be a mechanism whereby the cells could more effectively utilize phosphocholine to maintain a normal CDP-choline level in the choline-deficient liver.
Rat liver PE N-methyltransferase catalyzes all three transmethylation reactions in the conversion of PE to PC. The in vitro activity of PE N-methyltransferase was increased in choline-deficient livers using endogenous PE as the methyl group acceptor. However, no significant changes were observed in the enzyme activity when exogenous PMME was used as the methyl group acceptor. Addition of methionine to the cultured hepatocytes obtained from choline-deficient rats resulted in a concomitant reduction in cellular PE levels and the specific activity of PE-dependent methyltransferase. However, the specific activity of PMME-dependent methyltransferase was not significantly altered upon the addition of methionine. No change in PE N-methyltransferase activity was observed in the cultured hepatocytes supplemented with choline. Immunoblotting of PE
N-methyltransferase, in crude liver microsomes and in membrane fractions of cultured hepatocytes, revealed that the enzyme mass was not altered by choline and methionine deficiency. Thus, hepatic PE N-methyltransferase is preserved in choline deficiency, and its activity is probably dependent on the availability of metabolic substrates (i.e. methionine and PE).Medicine, Faculty of
Biochemistry and Molecular Biology, Department of
Graduate