Bibliografías temáticas / Chromogenic substrates

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Literatura académica sobre el tema "Chromogenic substrates"

Autor: Grafiati
Publicado: 4 de junio de 2021
Última modificación: 19 de febrero de 2022

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Artículos de revistas sobre el tema "Chromogenic substrates"

1

Hutton, R. A. "Chromogenic substrates in haemostasis". Blood Reviews 1, n.º 3 (septiembre de 1987): 201–6. http://dx.doi.org/10.1016/0268-960x(87)90036-1.

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Burrous, Mary R. y John Westley. "Chromogenic substrates for sulfurtransferases". Analytical Biochemistry 149, n.º 1 (agosto de 1985): 66–71. http://dx.doi.org/10.1016/0003-2697(85)90477-4.

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Hortin, Glen L., Ilka Warshawsky y Maryline Laude-Sharp. "Macromolecular Chromogenic Substrates for Measuring Proteinase Activity". Clinical Chemistry 47, n.º 2 (1 de febrero de 2001): 215–22. http://dx.doi.org/10.1093/clinchem/47.2.215.

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Abstract Background: Proteinase activities are often measured using chromogenic substrates that are much smaller than physiological substrates. Methods: The hydrodynamic size of macromolecular substrates (macrosubstrates) prepared by linking small chromogenic substrates to polyethylene glycol was determined by gel filtration. Efficiency of macrosubstrate cleavage by proteinases and α2-macroglobulin-proteinase complexes was monitored spectrophotometrically. Results: Macrosubstrates had hydrodynamic radii of ∼20 Å, similar to proteins with a molecular weight of 18 000. Different macrosubstrates served as efficient substrates for chymotrypsin, trypsin, and thrombin. Linking small substrates to a polymer variably affected substrate efficiency, with the impact on activity ranging from a 60-fold decrease to a 30-fold increase. Proteinases complexed with α2-macroglobulin had ∼10-fold lower activity vs macrosubstrates than small substrates. Conclusions: Macrosubstrates are efficient substrates that allow decreased measurement of sterically hindered proteinase molecules such as α2-macroglobulin-proteinase complexes. Thus, macrosubstrates may provide more accurate functional assays of proteinases such as coagulation factors.
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Johnson, Gary M. y Robert Schaeper. "Chromogenic Lactate−Leukocyte Esterase Substrates". Bioconjugate Chemistry 8, n.º 1 (enero de 1997): 76–80. http://dx.doi.org/10.1021/bc960081h.

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Marmuse, Laurence, Michèle Asther, David Navarro, Laurence Lesage-Meessen, Marcel Asther, Sébastien Fort y Hugues Driguez. "Chromogenic substrates for feruloyl esterases". Carbohydrate Research 342, n.º 15 (noviembre de 2007): 2316–21. http://dx.doi.org/10.1016/j.carres.2007.06.004.

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Conyers, Susan M. y David A. Kidwell. "Chromogenic substrates for horseradish peroxidase". Analytical Biochemistry 192, n.º 1 (enero de 1991): 207–11. http://dx.doi.org/10.1016/0003-2697(91)90208-b.

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Marmuse, Laurence, Michèle Asther, Emeline Fabre, David Navarro, Laurence Lesage-Meessen, Marcel Asther, Michael O'Donohue, Sébastien Fort y Hugues Driguez. "New chromogenic substrates for feruloyl esterases". Organic & Biomolecular Chemistry 6, n.º 7 (2008): 1208. http://dx.doi.org/10.1039/b717742a.

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Somorin, O., W. Okiei, T. Emokpae y M. Ogunlesi. "New lysine chromogenic substrates for trypsin". International Journal of Biological Macromolecules 9, n.º 1 (febrero de 1987): 27–31. http://dx.doi.org/10.1016/0141-8130(87)90021-3.

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Bozic, Natasa, Biljana Dojnov, Aleksandra Milovanovic, Vera Nenadovic, Jelisaveta Ivanovic y Z. Vujcic. "Characterization of endopeptidases from the midgut of Morimus funereus (Coleoptera: Cerambycidae) larvae". Archives of Biological Sciences 60, n.º 3 (2008): 403–9. http://dx.doi.org/10.2298/abs0803403b.

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Application of specific chromogenic substrates, use of class-specific inhibitors, and zymogram analysis enabled us to identify several peptidase classes in extracts of the midgut of Morimus funereus larvae. Zymogram analysis with gelatin as a peptidase substrate and phenylmethylsulfonyl fluoride as an inhibitor showed that serine peptidases were the most abundant endopeptidases in the midgut of M. funereus larvae. By zymogram analysis with gelatin as a peptidase substrate and 1,10-phenanthroline as an inhibitor, metallopeptidases were also detected. Analyses of serine peptidases with specific chromogenic substrates revealed dominance of elastase-like peptidases in extracts of the midgut of M. funereus larvae, with less pronounced chymotrypsin- and trypsin-like activities.
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10

Mašková, Hana P., George Kokotos, Chryssa Tzougraki y Tomislav Barth. "Synthesis and use of an aminoquinolinone derivative for the fluorometric determination of oxytocinase". Collection of Czechoslovak Chemical Communications 54, n.º 10 (1989): 2802–8. http://dx.doi.org/10.1135/cccc19892802.

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A new fluorogenic substrate for the determination of the activity of human serum oxytocinase-cystine aminopeptidase (EC 3.4.11.3), H-Cys(Bzl)-NH-Meq, has been synthesized. The affinity of H-Cys(Bzl)-NH-Meq to oxytocinase was by two orders higher than that of the usually employed chromogenic substrates. The Michaelis constant of oxytocinase for this substrate was within the range of the optimum pH (7.0–7.5) 2.3.10-6 mol l-1, i.e. in the region of the affinity of the natural substrate, oxytocin. The concentration of dimethylsulfoxide used for the solubilization of H-Cys(Byl)-NH-Meq (<0.4%) did not influence adversely the course of the enzyme reaction as in the case of chromogenic substrates, where the concentrations of the organic solvent exceeded 3%.
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Tesis sobre el tema "Chromogenic substrates"

1

Davidson, Gwen. "The development of chromogenic substrates for microbial detection". Thesis, University of Reading, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.731708.

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Various aspects in the field of chromogens were studied. In a multifaceted approach, investigations into their synthesis, coupling to less common sugars, and screening as substrates for biological activity, together with kinetic studies on the rate of hydrolysis of indoxyl substrates were carried out. A three-step route to synthesise substituted indoxyl chromogens was successfully developed. This method was subsequently used to prepare a number of halogen derivatives to study the effect of halogen type and position of substitution on the reaction yields. Overall yields range between 2 and 27 %. However attempts to make /V-alkyl indoxyl derivatives were unsuccessful. Studies were carried out to extend the range of target glycosidases by coupling indoxyl to a range of less common pentose and hexose sugars. The following sugars were successfully coupled; D- and L-glucose, D- and L-iyxose, D-galactose, L-rhamnose, 2-deoxy-D-ribose and acetyl-D-xylofuranose. The syntheses of indoxyl aminopeptidase substrates were successfully carried out using L- and D-alanine and L-pyroglutamic acid, with overall yields of between 1 and 3%. An ALDOL™ phosphatase substrate was synthesised with an overall yield of 18%. Studies determined that it was potentially suitable as both a fluorogenic and a chromogenic substrate. Agar based testing indicated that Clostridium perfringens could be successfully detected at a concentration 2.5 x 102 CFU/mL. The substrate was also found to fluoresce plastics. An agar method was developed to screen a range of key microorganism targets with indolyl substrates. The optimised method included the use of agar multipoint inoculators with 3mm pins, by inoculating 1.5 x 108 CFU/mL into nutrient agar containing chromogenic substrate (50mg/100mL), and incubating at 37 °C for 24 hours. Using quantitative UV-Vis and HPLC analyses, techniques to monitor the hydrolysis of indoxyl galactosides were developed and used to correlate molecular structure with rates of hydrolysis. Rates were observed to increase in the order unsubstituted
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2

Sidibeh, Cherno Omar. "Production and cleavage specificity determination of serine proteases mMCP-4, mMCP-5, rMCP-2 and two platypus serine proteases of the chymase locus". Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-197088.

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Serine proteases are a family of enzymes with a wide array of functions across both eukaryotes and prokaryotes. Here we have attempted to produce the serine proteases rat mast cell protease 2 and mouse mast cell protease 5 in a culture of HEK 293 cells; and mouse mast cell protease 4, platypus granzyme B-like protease and platypus hypothetical protease in a baculovirus expression system. Following production we wanted to analyse these serine proteases using a phage display assay and a battery of chromogenic substrates.
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Huang, Zheng. "Studies of novel chromogenic substrates and immunomagnetic separation techniques for microbiological characterization and detection". Thesis, King's College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415119.

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Gamage, Sujatha Nandani. "A study of catalytic autoxidation of organic substrates using H2/O2 mixtures in the presence of rhodium complexes containing dimethylsulfoxide ligands". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25791.

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Dimethylacetamide (DMA) solvent is oxidized catalytically to CH₃CON(CH₃)CH₂OOH and CH₃CON(CH₃)CHO under H₂/0₂ mixtures at 50°C in the presence of the dimethylsulfoxide complex RhCl₃(DMSO)₃ (I) at a rate which is much faster than peroxide-initiated autoxidation of DMA under O₂ alone. The hydroperoxide is thought to be the initial product, and the N-formyl derivative its decomposition product. An accompanying metal-catalyzed hydrogenolysis of 0₂ leads to H₂0₂ and H₂0. Hydrogen peroxide and CH₃CON(CH₃)CH₂OOH are the only products formed in the early stages of the catalytic reaction. The maximum rate of gas uptake in this initial region is independent of the partial pressure of 0₂, but shows linear dependences on Rh and H₂. Stoichiometry, rate and spectral data are consistent with an initiation reaction between complex I and H₂, and then 0₂ to give a catalytically active RhIII (0₂=) (DMA) species (II) (eq. 1) [formula omitted] The autoxidation of DMA and the hydrogenolysis of 0₂ are postulated to occur via independent pathways involving II (eqs. 2 and 3). [formula omitted] In the absence of H2, II degenerates to catalytically inactive species. The role of H₂ in the DMA autoxidation is thought to be the regeneration of Rh I species and hence II, from deactivated forms of II. Eventual slow, irreversible deactivation of the catalyst and the probable participation of the H₂0₂ product in peroxide initiated free-radical autoxidations complicate the interpretation of later stages of reaction. Diphenylsulfide (DPS) is catalytically oxidized to the sulfoxide by complex I under H₂/O₂ in DMA at 50°C, but accompanying oxidation of the solvent persists even in the presence of a 100-fold excess of DPS over Rh. Oxidation of the sulfide is thought to involve H₂0₂ liberated in the catalytic hydrogenolysis of 0₂. Complex I in CH₂C1₂ or C₂H₄CL₂ reacts with CO to give the dimethylsulfide complex RhCL₃(DMS)₃ via a facile reduction of DMSO ligands. Dimethylsulfoxide is reduced also by RhI species in CH₂CL₂ in the presence of two equivalents of acid to yield DMS, RhIII and H₂0. However, Rh I /2H⁺/DMS0 systems are relatively stable in DMA, because of the proton affinity of the solvent. Complex I reacts also with the strongly basic tertiary amine NEt₃ via a redox process in which the RhIII is reduced to Rh I with an accompanying dehydrogenation of the amine (eq. 4). RhCl₃ + 3NEt₃ → RhCl + 2NEt₃ HCl + CH₂=CHNEt₂ (4) The resulting ethenamine then reacts with I to give the ƞ¹-ylidic complex, RhCl₃(DMS̠O)₂(⁻CH₂CH=⁺NEt₂). Data from an earlier thesis, on a reaction between complex I and 1,8-bis(dimethylamino)naphthalene (or Proton Sponge), are reinterpreted in terms of a similar redox reaction that gives an N-carbene fragment (eq. 5),which is stabilized within the RhIII complex, RhCl₃(DMS̠O)₂(=CH-N(Me)-C₁₀H₆NMe₂•HCl). [formula omitted]
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5

Bedernjak, Alexandre. "Synthesis and biological evaluation of novel chromogenic substrates for the enhanced detection of pathogenic bacteria". Thesis, University of Sunderland, 2010. http://sure.sunderland.ac.uk/6561/.

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The present work investigated the preparation of phenoxazinone derivatives and evaluated their performances for the detection of pathogenic bacteria. The first method investigated the condensation of nitroaminophenol with tetrahalogenobenzoquinones; the corresponding nitrohalogenophenoxazinones were all characterised and evaluated for the detection of nitroreductase activity in a range of clinically important microorganisms. The detection of nitroreductase activity has been previously suggested for the monitoring of bacterial growth; however, nitrohalogenophenoxazinones were proven to be less suitable for this purpose than other, previously reported, nitroreductase substrates. The second route investigated the synthesis of phenoxazinone derivatives via the oxidative cyclisation of diamino-dihydroxydiphenylethers and of diaminobenzoquinones. The reactive intermediates were trapped and characterised in order to rationalize the mechanism of formation of aminophenoxazinones via this route. 7- and 8-Aminophenoxazinones derivatives were prepared and further derivatised with b-alanine. Similarly, some nitrohalogenophenoxazinones were reduced to their corresponding aminophenoxazinones and derivatised with b-alanine. Thirteen new chromogenic substrates were prepared, characterised and evaluated for their sensitivity to detect b-alanine aminopeptidase on agar medium; this enzyme is expressed by only three types of bacteria, the most important being Pseudomonas aeruginosa, a pathogen commonly known to affect cystic fibrosis sufferers. Their performance for the detection of Pseudomonas aeruginosa were compared to the lead compound (7-N-(b-alanyl)amino-1-pentylphenoxazin-3-one), the substrate contained in a commercially available medium, chromIDTM ID Ps. aeruginosa. The substrates, if hydrolysed, resulted in a low colouration of the colonies when compared to the lead compound; however, 2-pentyl substituted aminophenoxazinones were found to be less toxic and had an excellent affinity for the bacterial colonies.
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6

Abuaita, Areej y Saleh Asmaa El. "Utvärdering av analysmetod för bestämning av anti-FXa aktivitet i plasma hos patienter behandlade med apixaban eller LMH". Thesis, Hälsohögskolan, Högskolan i Jönköping, HHJ, Avd. för naturvetenskap och biomedicin, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-45236.

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Apixaban och lågmolekylärt heparin (LMH) är antikoagulantia som förhindrar blodproppsbildning genom att hämma faktor Xa. Allt mer patienter använder apixaban och LMH, vilket gör att laboratoriemedicin på länssjukhuset Ryhov är i behov av att utvärdera analysmetoder för apixaban och LMH för att kunna implementera analyserna i klinisk rutin. Syftet med studien var att utvärdera analysmetoden för bestämning av anti-FXa aktivitet i plasma hos patienter behandlade med apixaban eller LMH med hjälp av kromogen substratmetod. Metodutvärderingen bestod av fyra steg: repeterbarhet, mellanliggande precision, överensstämmelse med validerad metod och analys av normalpopulation. Utvärderingen genomfördes med hjälp av Sysmex CS-2100 där det analyserades 20 respektive 40 patientprover för apixaban och LMH samt 10 normalprover. Aktivitet av faktor Xa bestämdes kvantitativt med användning av ljusabsorption vid 405 nm. Repeterbarhet och mellanliggande precision visade låg CV. Patientprover visade överensstämmande resultat med referensvärden från andra laboratorium där r2 för apixaban och LMH var 0,95. Avvikande resultat kan bero på mätfel eller förväxling mellan prover. Analys av normalpopulation visade att värden låg under det lägsta tillförlitliga värdet. Utvärdering av analysmetoden apixaban och LMH på Ryhovs laboratorium visade goda resultat vilket bekräftar att analysmetoden kan användas i klinisk rutin.
Introduction: Apixaban and low molecular weight heparin (LMWH), are anticoagulants that prevent clot formation by inhibiting factor Xa. Increasingly more patients use apixaban and LMWH, for this reason the laboratory medicine at the county hospital Ryhov needs to evaluate methods of analysis for apixaban and LMWH to be able to implement the analyzes in clinical routine. Aim: The purpose of the study was to evaluate the assay method for determining anti-FXa activity in plasma in patients treated with apixaban or LMWH using chromogenic substrate method. Method: The method evaluation consisted of four steps: repeatability, intermediate precision measures, compliance with validated method and analysis of normal population. The evaluation was performed using Sysmex CS-2100 where 20 respective 40 patient samples were analyzed for apixaban and LMWH as well as 10 normal population samples. Factor Xa activity was quantitatively determined using light absorption at 405 nm.Result and discussion: Repeatability and intermediate precision showed low CV. Patient samples showed consistent results with reference values from other laboratories where r2 for apixaban and LMWH were 0.95. Deviant results may be due to measurement errors or confusion between samples. Analysis of normal population showed that values were below the lowest reliable value. Conclusion: Evaluation of the analysis method apixaban and LMWH at Ryhov's laboratory showed good results, which confirms that the assay method can be used in clinical routine.
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Chen, Jo-Chin y 陳若瑾. "3D-Printed, Peroxidase Mimic/Chromogenic Substrate-Incorporated Multi-Well Device for in Situ Glucose Determination". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/w3er3z.

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碩士
國立清華大學
生醫工程與環境科學系
105
Nanomaterials with intrinsic peroxidase-like activities have been demonstrated as promising artificial enzymes for numerous biochemical applications. In recent years, three dimensional printing (3DP) technologies have accelerated the customization and rapid prototyping of multilayer components/devices in general laboratories for a wide range of analytical applications. In this study, to enable the 3D-printed devices to have both the peroxidase and chromogenic activities, a multi-well plate is one-step printed using a dual-head fused deposition modeling-type 3D printer with two functionalized thermoplastic filaments, acrylonitrile butadiene styrene incorporated with peroxidase-mimicking iron oxide (Fe3O4) nanoparticles and polyvinyl alcohol infiltrated with chromogenic substrate o-phenylenediamine (OPD). The fabricated plates are confirmed to efficiently catalyze the oxidation of OPD by peroxidase substrate H2O2 and allow measurement of the absorbance of the derivatized samples through directly loading it into a conventional plate reader. After method’s optimization, the method’s detection limits can reach as low as 2.8 μM for H2O2 and 5.0 μM for glucose. Based on our demonstrations, the proposed 3D-printed peroxidase mimic/chromogenic substrate-incorporated multi-well plates can provide the competitive peroxidase activities, in-well derivatization and measurement/visualization without any sample transfer, and the applicability of in situ, rapid, high-throughput analyses of glucose concentrations in clinical samples.
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Libros sobre el tema "Chromogenic substrates"

1

Lijnen, H. R. Synthetic Substrates in Clinical Blood Coagulation Assays. Springer, 2011.

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Witt, Irene y Deutsche Gesellschaft für Klinische Chemie. New methods for the analysis of coagulation using chromogenic Substrates: Proceedings of the symposium of the Deutsche Gesellschaft für Klinische Chemie, Titisee, Breisgau, West-Germany, July 1976. De Gruyter, Inc., 2019.

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Capítulos de libros sobre el tema "Chromogenic substrates"

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Kirschke, H. y B. Wiederanders. "Chromogenic Peptide Substrates". En Proteolytic Enzymes, 11–29. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-642-59816-6_2.

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Porstmann, Bärbel y Tomas Porstmann. "Chromogenic Substrates for Enzyme Immunoassay". En Nonisotopic Immunoassay, 57–84. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4684-5466-6_3.

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Zhang, Ruo-heng, Xue Ge, Xiao-jie Xu y You-qi Tang. "Kinetic investigation of the chromogenic peptide substrates for chymotrypsin". En Peptides, 278–79. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-010-9066-7_81.

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Biely, Peter. "Differentiation of Glycanases of Microbial Cellulolytic Systems Using Chromogenic and Fluorogenic Substrates". En Extracellular Enzymes of Microorganisms, 187–92. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4684-1274-1_23.

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Rijkers, D. T. S., H. C. Hemker y G. I. Tesser. "Peptide p-nitroanilides: Chromogenic substrates for the determination of the thrombin generation curve". En Peptides 1994, 901–2. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-1468-4_415.

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Friberger, P. "Use of Chromogenic Peptide Substrates in the Study of Proteolytic Enzymes and Mechanisms Regulating them". En Cells, Membranes, and Disease, Including Renal, 327–33. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4684-1283-3_34.

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Schückel, Julia y Stjepan Krešimir Kračun. "Two-Dimensional High-Throughput Endo-Enzyme Screening Assays Based on Chromogenic Polysaccharide Hydrogel and Complex Biomass Substrates". En Cellulases, 201–17. New York, NY: Springer New York, 2018. http://dx.doi.org/10.1007/978-1-4939-7877-9_15.

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Aasen, A. O. "Chromogenic Peptide Substrate Assays". En Update in Intensive Care and Emergency Medicine, 141–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-83042-6_16.

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Pennington, M. W., S. M. Festin, M. L. Maccecchini, F. Dick y P. E. Scarborough. "HIV protease, chromogenic substrate and inhibitor". En Peptides 1990, 787–89. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3034-9_326.

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Hahn-Hägerdal, Bärbel y Anneli Svensson. "A Chromogenic Substrate Limulus Assay Applied to Raw Milk". En MILK the vital force, 132. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-3733-8_110.

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Actas de conferencias sobre el tema "Chromogenic substrates"

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Stüber, W., D. Schiwek, U. Becker y N. Heimburger. "NEW CHROMOGENIC SUBSTRATES FOR THE DETERMINATION OF COAGULATION AND FIBRINOLYSIS ENZYMES". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644323.

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A new type of chromogenic substraces based on derivatives of phenoxazine is presented. Particularly interesting is the blue dye 7-amino-3-diethylamino-8-methylphenoxazine (ADMP) with a molar extinktion coefficient of about 80,000 at 624 nm. Peptides were linked to the aminogroup of the dye and red coloured substrates were obtained with a λmax value of about 540 nm. On account of the distinct difference of the λmax values and the negligable influence of the absorption peaks of the acylated and the free dye this chromophore is suitable for the synchesis of substrates. Besides the spectral properties of chese new chromogenic peptides we determined their characce-riscics using serine proteases involved in the process of coagu-lacion and fibrinolysis. In comparison co para-nitroaniline substrates the introduction of the relatively bulky ADMP into the peptide sequence led to products with superior properties in respect of sensitivity and specificity.It was found that the ADMP substrates are particularly favourable for the determination of thrombin, urokinase and activated protein C in the presence of other proteases.
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Baumann, Martin J., Tuula T. Teeri y Harry Brumer. "SYNTHESIS OF CHROMOGENIC AND FLUOROGENIC XYLOGLUCO-OLIGOSACCHARIDES AS SUBSTRATES FOR ENDOGLUCANASES AND XYLOGLUCAN ENDOTRANSGLYCOSYLASES". En XXIst International Carbohydrate Symposium 2002. TheScientificWorld Ltd, 2002. http://dx.doi.org/10.1100/tsw.2002.730.

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Siekmann, U., D. Dittrih y R. E. Zimmermann. "PHOTOMETER-LINKED MICROCOMPUTER SYSTEM ENABLES PRECISE CHROMOGENIC PROTHROMBIN TIME ASSAYS". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644809.

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In coagulation diagnostics photometric assay procedures are in widespread use. Due to the availability of new specific chromogenic peptide substrates, automated instruments play an important role in clinical routine laboratory diagnosis. For research work, the benefit of expensive industrial photometric coagulation systems is questionable, especially as the program cannot be adapted by the user. For this purpose we developed an inexpensive microcomputer-controlled measuring system as well as a suitable photometric assay which allows to determine chromogenic clotting times with any conventional spectrophotometer.Absorbance data were taken from the analog chart-recorder output of a double-beam spectrophotometer, digitized by a 12 bit analog-to-digital converter and read by the computer via an interface. Menu driven, user orientated / user dialogue based compiled BASIC software was written to enable data acquisition and processing.During the chromogenic assay procedure, automatically collected absorbance data were displayed, stored, analyzed immediately, saved on disk for later kinetic analysis and printed.Preliminary results with our chromogenic PT-assay indicate excellent reproducabi1ity of the test. The clotting time itself is defined as the interval from the beginning of the test to the moment when a preselected absorbance change occurred. Standard curves can automatically be calculated by regression routines after measurement of reference values.It must be emphasized that the occurence of fibrinogen-generated turbidity during the chromogenic assay sometimes influences the total absorbance significantly. For this reason the reaction time has to be limited by a low optical endpoint setting.
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4

Fenton, J. W., J. I. Witting y T. M. Miller. "THROMBIN KINETIC PARAMETERS WITH TRIPEPTIDE p-NITROANALIDES UNDER PHYSIOLOGICALLY RELEVANT CONDITIONS". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643278.

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The Michaelis-Menten (Km ), catalytic (kcat ), and specificity (kcat/Km ) constants were determined for humSft α- and β-thrombins with the chromogenic substrate S-2238 (H-D-Phe-Pip-Arg-pNA), Chromozym-TH (Tos-Gly-Pro-Arg-pNA), and Spectrozyme-TH (H-D-HHT-Ala-Arg-pNA) in 0.15 M NaCl buffered with 10 mM HEPES ancTlO mM Tris-HCT at pH 7.4, 37°C. Spontaneous hydrolysis was insignificant for these substrates. Both S-2238 and Spectrozyme-TH exhibited limiting solubilities at ∼35 μM, while Chromozym-TH did not do so up to 50 μM. From initial estimates, Km's and k t's were refined by computer Gause-Newton iterations or nonlinearneast-square fits for the concentration of p-nitroanalide formed per second versus the initial substrate concentration. No major differences were found between a-thrombin (99% α, 91% esterolytically active enzyme, and > 3,500 kilo-U.S. clotting units/g with fibrinogen) and Yγ-thrombin (98% γ. 89% active enzyme, and < 10 kilo-units/g). For α- versus γ-thrombin and the three substrates, respectively, the Km 's were 6.75 ± 0.13 vs 7.62 ± 0.30, 18.4 ± 0.4 vs 23.0 ± 0.3, and 2.53 ± 0.02 vs 3.85 ± 0.51 μM; the kcat> s were 125 ± 1 vs 134 ± 2, 181 ± 2 vs 130 ± 1, and 35.5 ± 0.2 vs 52.4 ± 2.0 s−1 ; and the kcat/Km 's were 18.5 vs 17.6, 9.84 vs 5.65, and 10.1 vs 13.6 s−1 μm . These values closely approximate those of 7.2 ± 0.9 μM, 84 ± 4 s−1 , and 11.7 s−1 μM−1 determined by Higgins, Lewis, and Shafer (J. Biol. Chem. 258:9276-9282, 1983) for the Aα cleavage of human fibrinogen by human α-thrombin under physiologically relevant conditions. Thus, these chromogenic substrates have thrombin specificities similar to that of fibrinogen, although their amidolytic activities are independent of additional active-site regions required for fibrinogen clotting activity (α vs γ-thrombin). Fibrinogen interactions with such active-site regions might account for why the fibrinogen Aa site is an atypical thrombin susceptible bond and the high species variability of fibrinopeptides. (Supported in part by NIH grant HL-13160).
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5

Tans, G., T. Janssen-Claessen, J. Rosing y J. H. Griffin. "APPLICATION OF SPECIFIC SERINE PROTEASE INHIBITORS IN ASSAYS FOR ACTIVATED CONTACT FACTORS." En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643301.

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We developed amidolytic assays to determine human Factor Xlla, Factor XIa and plasma kallikrein in mixtures containing variable amounts of each enzyme. The commercially available chromogenic substrates pro-phe-arg-pNA (S2302 or chromozym PK), glu-pro-arg-pNA (S2366), ile-glu-(piperidyl)-gly-arg-pNA (S2337), and ile-glu-gly-arg-pNA (S2222) were tested for their suitability as substrates in these assays. 8-Factor Xlla, Factor XIa and plasma kallikrein each exhibit considerable activity towards a number of these substrates. This precludes direct quantitation of the individual enzymes when large amounts of other activated contact factors are present. Several serine protease inhibitors were tested on their ability to selectively inhibit those contact factors that may interfere with the factor tested for. Soybean trypsin inhibitor efficiently inhibits kallikrein, inhibits Factor XIa at moderate concentrations, but did not affect the amidolytic activity of Factor Xlla. Therefore, this inhibitor can be used to abolish a kallikrein and Factor XIa contribution in a Factor Xlla assay. We also report the rate constants of inhibition of contact activation factors by three different chloromethylketones. D-phe-pro-arg-CH 2 Cl was moderately active against contact factors (k - 2271 M-ls-1 at pH 8.3) but showed no differences in specif ity. D-phe-phe-arg-CH2 Cl was a very efficient inhibitor of kallikrein (k = 118,000 M-ls-1 at pH 8.3) whereas it slowly inhibited Factor Xlla (k = 1389 M-ls-1) and Factor XIa (k = 110 M-ls-1). Also dansyl-glu-gly-arg-CH2Cl was more reactive towards kallikrein (k 15,662 M-ls-1) than towards Factor Xlla (k = 462 M-ls-1) and Factor XIa (k = 63 M-ls-1). Since phe-phe-arg-CH2Cl is highly specific for kallikrein it can be used in a Factor XIa assay to selectively inhibit kallikrein. Based on the catalytic efficiencies of chromogenic substrate conversion and the inhibition characteristics of serine protease inhibitors and chloromethyl ketones we were able to develop quantitative assays for Factor Xlla, Factor XIa and kallikrein in mixtures of contact activation factors.
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6

Exner, T. "CONCENTRATION DEPENDENCE OF ACTIVATION OF ACARBOXYPROTEIN C BY THE CONTORTRIX ACTIVATOR". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644301.

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The protein C activator in Southern Copperhead (Agkistrodon Contortrix Contortrix) venom was isolated by sequential chromatographies on SP�Sephadex, Con A Sepharose and hydroxylapatite. It was found to be a single chain glycoprotein with an apparent molecular weight of 36,000 and an enzymatic specificity on chromogenic substrates resembling kallikein.This "contortrix activator" was used in a solid-phase immunochromometric assay (ICMA) for functional protein C in which heterologous antibody against protein C was passively coated onto microtitre wells and used to immoblize protein C. This was then activated, easily freed of excess activator by washing and assessed by its subsequent overnight cleavage of chromogenic substrates sensitive to activated protein C.Correlation between protein C results obtained by ICMA and immunoradiometric assay (IRMA) on a variety of patient samples was excellent when relatively high concentrations of the venom activator was used. However with lower concentration of activator plasmas from patients deficient in vitamin K gave lower protein C values by ICMA then obtained by IRMA.Normal protein C and "acarboxy" protein C from a patient on oral anticoagulant therapy were immuno-immobilized and studied by the ICMA technique using varying concentrations of the venom activator. The acarboxy-protein C, although completely activatable by high concentrationa of activator, was found to activate much more slowly than normal protein C at low concentrations of the contortrix activator. Thus by reducing the intensity of the activation step, the ICMA protein C results were increased in their sensitivity for functional protein C.
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7

Chmielewska, J. y B. Wiman. "ON THE KINETICS OF THE INHIBITION OF PLASMINOGEN ACTIVATORS BY THE PLASMINOGEN ACTIVATOR INHIBITOR PAI-1". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642808.

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The kinetics of the inhibition of the following plasminogen activators: one- and two-chain tissue plasminogen activator (t-PA) and low and high molecular weight urokinase (UK) by PAI-1 was studied. For this purpose direct systems were employed and the reactions were studied in the presence of different concentrations of plasminogen activator chromogenic substrates. The second-order rate constant of the association reaction was estimated from the initial decline in plasminogen activator activity. Determination of the rate constants in the absence of substrates was performed by plotting the rate constants versus the substrate concentrations and extrapolation to zero concentration. The rate constants with all plasminogen activators were very similar and estimated as 2 - 4 x 107 M-1 x s-1. The reactions were also studied in the presence of 6-aminohexanoic acid, lysine, arginine, guanidinium chloride (final concentrations for all substances about 1 mmol/L) and heparin (10 mg/L), without any significant effect on the rate constants. The effect of soluble fibrin (bathroxobin-digested fibrinogen in urea) at 10 - 300 nmol/L was also studied. With one-chain t-PA the rate constant was decreased about 10-fold with the highest fibrin concentration and about 2-fold at 30 nmol/L. In contrast, the reactions with urokinase or two-chain t-PA were not influenced by fibrin at these concentrations. These findings may have a physiological significance: the one-chain t-PA adsorbed to the fibrin surface and actively involved in fibrinolysis would be protected against inactivation by PAI. This phenomenon adds further to the physiological fibrin specificity of one-chain t-PA.
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8

Ellis, V., M. F. Scully y V. V. Kakkar. "PLASMINOGEN ACTIVATION BY SINGLE-CHAIN UROKINASE (scu-PA) IN FUNCTIONAL ISOLATION - DEMONSTRATION OF A NOVEL MECHANISM". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642907.

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The kinetics of the activation of Glu- and Lys- plasminogen by single-chain urokinase (pro-urokinase) derived from the transformed human kidney cell line, TCL-598, has been studied and compared with two-chain urokinase (UK). Plasminogen activation was determined by the change in fluorescence polarization of fluorescein-labelled aprotinin (Trasylol), an essentially irreversible inhibitor of plasmin. This methodology allows plasmin production by scu-PA to be measured in functional isolation, with no interfering generation of two-chain UK. scu-PA was found to activate plasminogen to plasmin with Michaelis-Menten type kinetics. The Km for this reaction was determined as 70µM, with a catalytic constant of 2.25 min-l. The generation of two-chain plasmin was confirmed by reduced SDS-PAGE. Plasminogen activation by UK was found to have a similar Km but the kcat was 16-fold higher, at 36.0 min-l. This is in contrast to the amidolytic activity of scu-PA which was less than 0.2% that of UK. The activation of scu-PA to UK by plasmin was also characterized. Using these data it is possible to calculate the theoretical rate of plasminogen activation by scu-PA, in the absence of aprotinin when UK will be generated by plasmin action. The calculated rate was in good agreement with that determined experimentally when using the chromogenic substrate, S-2251. These data demonstrate that scu-PA has properties which distinguish it from conventional serine protease zymogens. There is a lack of activity against peptide substrates (and also DFP) demonstrating the inaccessibility of the substrate binding pocket. However, there is moderate activity against plasminogen suggesting that plasminogen may be acting as both an effector and a substrate for scu-PA.
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9

Chabbat, J., L. Pejaudier, V. Kichenin-martin, S. Hampikian-Le Nin y M. Steinbuch. "PROPERTIES OF A F VII CONCENTRATE." En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643282.

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A concentrate of factor VII obtained by adsorption onto an inorganic adsorbent using a by-product of routine fractionation as starting material This fraction contains only small amounts of the other constituents of the prothrombin complex ( PC ) but it is enriched in proteins C and S. It contains much less VIII CAg than the usual even activated PC concentrates. The amounts of isoagglutinins anti-A and B have also been checked. The concentrate of partially versus completely activated factor VII ( by factor Xlla ) has been submitted to animal experiences including those effected on hemophilic dogs. The concentrate and highly purified factor VII prepared from it were checked on a serie of chromogenic substrates and inhibitors of proteolytic enzymes of plasmatic and other origin. The results obtained are compared with those given by the two most commonly used activated PCCs. The correlation between active F VII and by-passing activity has been studied. This concentrate might thus be indicated for the treatment of hemophilia A-patients with inhibitors.
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10

Petersen, L. C., M. Johannessen, D. Foster, A. Kumar y E. Mulvihill. "CATALYTIC ACTIVITIES OF ONE-CHAIN tPA AS REVEALED BY AN ANALOGUE RESISTANT TO PLASMIN CLEAVAGE". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643845.

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Substitution of Arg275 with Gly in the activation site of tPA provides a one-chain recombinant analogue, tPA-Gly275, which is very resistant to cleavage by plasmin. The amidolytic activity of tPA-Gly275 with simple synthetic substrates was investigated and compared to the kinetics obtained with authentic one- and two-chain tPA. Both one-chain (zymogen) forms possess enzymatic activity, however, in the absence of fibrin it is much lower than that of two-chain tPA. Fibrin enhances the activity of the one-chain tPA forms, but not of two-chain tPA.A chromogenic assay was developed for measurement of plasminogen activation. Due to the presence of a high affinity plasmin substrate (D-Val-Phe-Lys-pNA) and aprotinin in the reaction mixture, the assay ensures a low steady-state concentration of free plasmin during the measurement. With this assay and with tPA-Gly275 it is possible to measure plasminogen activation kinetics of one-chain tPA without any significant two-chain tPA formation even in the presence of fibrin. The intactness of tPA-Gly275 was confirmed by direct measurement of the one-/two-chain tPA content by means of reduced SDS-PAGE combined with Western blotting after exposure to plasmin digestion in the presence and absence of fibrin. The results suggest that one-chain tPA possesses enzymatic activity also with plasminogen as the substrate, however, the activity is much lower than that of two-chain tPA. Addition of fibrin profoundly enhances the plasminogen activation rate of both tPA-Gly275, one-chain, and two-chain authentic tPA to approx. the same maximal level. Taken together these observations indicate that fibrin binding can induce an activated state of the intact tPA ‘zymogen’
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