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1
Pexa, Annette. "Alimentäres Methionin und Hyperhomocysteinämie." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1168459718761-52550.
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Eine erhöhte Konzentration von Homocystein im Plasma (Hyperhomocysteinämie) gilt als unabhängiger Risikoindikator für neuronale und kardiovaskuläre Erkrankungen. Der Präcursor des Homocysteins, Methionin, ist eine essentielle Aminosäure, die bei Fehlernährung übermäßig verzehrt werden kann. Es wurde untersucht, ob tatsächlich durch langfristigen erhöhten Methioninverzehr via Erhöhung des Homocysteinspiegels im Plasma ein reales Gesundheitsrisiko besteht. Als Modell wurde eine Füttterungsstudie an Ratten gewählt, deren Bedingungen bezüglich Fütterungsdauer und Methioningehalt der Diät (0,4 % Methionin für 4 Wochen) an eine mögliche Fehlernährung des Menschen angepasst waren. Bei diesen Ratten war die Plasmahomocystein-Konzentration ca. 2-fach höher, als bei Ratten, die im gleichen Zeitraum eine "normale" Diät mit einem 3-4 fach niedrigeren Methioningehalt bekamen. Neben der Auswirkung der Diät auf den Homocystein-Stoffwechsel wurde geprüft, welche der in der Literatur dargestellten potentiellen Pathomechanismen für Hyperhomocysteinämie-induzierte Schäden Anwendung in diesem Modell finden. Obwohl die Konzentration von Homocystein im Plasma verändert war, wurde keine Beeinträchtigung der Gefäßfunktion gefunden. Auch die Plasmakonzentration von asymmetrischem Dimethylarginin, einem weiteren Risikoindikator für Herz-Kreislauf-Erkrankungen blieb unverändert, obwohl dieser Parameter bei Hyperhomocysteinämie oftmals erhöht ist. Eine Konzentrationsverdoppelung von Homocystein durch erhöhte alimentäre Methioninzufuhr ohne gleichzeitige Erhöhung von ADMA scheint also keine Verschlechterung der Gefäßfunktion bei Ratten zu bewirken. In diesem Punkt kann man von in anderen Modellen der Hyperhomocysteinämie gefundenen Resultaten keine Rückschlüsse auf die durch alimentäres Methionin verursachte Hyperhomocysteinämie ziehen. Andere Modelle zur Induktion einer Hyperhomocysteinämie ist Homocyst(e)in-Fütterung. In weiteren Rattenstudien wurden Effekte homocystin- und methioninreiche Diät verglichen. In diesen Studien zeigte sich, dass bei ähnlichen applizierten Dosen (tägliche Aufnahme ca. 1,0 bzw. 1,4 g/kg Körpergewicht) methionin- und homocystinreiche Diät bei Ratten zu vergleichbaren Plasma-Homocysteinspiegeln führen (methioninreich: 27,32 ± 2,80 µmol/l; homocystinreich: 40,61 ± 2,22 µmol/l). Als Vergleichsparameter zur Beurteilung pathophysiologischer Veränderungen diente zum einen der Gewebsgehalt an Homocystein, zum anderen wurden die intrazellulären Konzentrationen von S-Adenosyl-Methionin (SAM) und S-Adenosyl-Homocystein (SAH) betrachtet. Es zeigten sich besonders in Leber und Niere signifikante Unterschiede zwischen einer methioninreichen und einer homocystinreichen Diät bei Ratten. Dies ist eine mögliche Erklärung dafür, dass die bei vierwöchiger methioninreicher Diät gefundenen Ergebnisse nicht mit Literaturdaten übereinstimmen. Abschließend wurde der Frage nachgegangen, ob eine homocytinreiche Ernährung, wie in der vorherigen Studie angewandt, überhaupt möglich ist. Da zwar die Gehalte von Methionin in fast allen Lebensmitteln bekannt sind, nicht aber die von Homocystein, wurde untersucht, in welchen Konzentrationen Homocystein in Lebensmitteln enthalten ist. In Schwarzbier (0,03 mg/l), Weißbrot (0,95 mg/kg), Roquefort-Käse (0,50 mg/kg), Thunfisch (0,25 mg/kg) und Schweineleber (0,31 mg/kg) konnte Homocystein bestimmt werden. Da die Homocysteinkonzentrationen in diesen Beispiellebensmitteln mindestens um den Faktor 105 geringer waren als die Methioninkonzentrationen ist ein Einfluss von alimentärem Homocystein auf den Plasmaspiegel sehr unwahrscheinlich. Es wurde weiterhin geprüft, ob durch Darmbakterien ein Teil des alimentär aufgenommenen Methionins bereits im Dünndarm in Homocyt(e)in umgewandelt werden könnte. Dabei wurde eine vermehrte Homocysteinproduktion nach Methionin-Zugabe zu Dünndarmisolaten gefunden. Quantitativ kommt dieser Homocysteinquelle eine untergeordnete Bedeutung zu.
2
Reck, Andreas Michael. "Homocysteinstoffwechsel und Atherosklerose Methionin-Belastungstests und langfristige Methionin-Applikation im Kaninchenmodell /." [S.l. : s.n.], 2006.
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3
Pexa, Annette. "Alimentäres Methionin und Hyperhomocysteinämie." Doctoral thesis, Technische Universität Dresden, 2006. https://tud.qucosa.de/id/qucosa%3A24971.
Full textAbstract:
Eine erhöhte Konzentration von Homocystein im Plasma (Hyperhomocysteinämie) gilt als unabhängiger Risikoindikator für neuronale und kardiovaskuläre Erkrankungen. Der Präcursor des Homocysteins, Methionin, ist eine essentielle Aminosäure, die bei Fehlernährung übermäßig verzehrt werden kann. Es wurde untersucht, ob tatsächlich durch langfristigen erhöhten Methioninverzehr via Erhöhung des Homocysteinspiegels im Plasma ein reales Gesundheitsrisiko besteht. Als Modell wurde eine Füttterungsstudie an Ratten gewählt, deren Bedingungen bezüglich Fütterungsdauer und Methioningehalt der Diät (0,4 % Methionin für 4 Wochen) an eine mögliche Fehlernährung des Menschen angepasst waren. Bei diesen Ratten war die Plasmahomocystein-Konzentration ca. 2-fach höher, als bei Ratten, die im gleichen Zeitraum eine "normale" Diät mit einem 3-4 fach niedrigeren Methioningehalt bekamen. Neben der Auswirkung der Diät auf den Homocystein-Stoffwechsel wurde geprüft, welche der in der Literatur dargestellten potentiellen Pathomechanismen für Hyperhomocysteinämie-induzierte Schäden Anwendung in diesem Modell finden. Obwohl die Konzentration von Homocystein im Plasma verändert war, wurde keine Beeinträchtigung der Gefäßfunktion gefunden. Auch die Plasmakonzentration von asymmetrischem Dimethylarginin, einem weiteren Risikoindikator für Herz-Kreislauf-Erkrankungen blieb unverändert, obwohl dieser Parameter bei Hyperhomocysteinämie oftmals erhöht ist. Eine Konzentrationsverdoppelung von Homocystein durch erhöhte alimentäre Methioninzufuhr ohne gleichzeitige Erhöhung von ADMA scheint also keine Verschlechterung der Gefäßfunktion bei Ratten zu bewirken. In diesem Punkt kann man von in anderen Modellen der Hyperhomocysteinämie gefundenen Resultaten keine Rückschlüsse auf die durch alimentäres Methionin verursachte Hyperhomocysteinämie ziehen. Andere Modelle zur Induktion einer Hyperhomocysteinämie ist Homocyst(e)in-Fütterung. In weiteren Rattenstudien wurden Effekte homocystin- und methioninreiche Diät verglichen. In diesen Studien zeigte sich, dass bei ähnlichen applizierten Dosen (tägliche Aufnahme ca. 1,0 bzw. 1,4 g/kg Körpergewicht) methionin- und homocystinreiche Diät bei Ratten zu vergleichbaren Plasma-Homocysteinspiegeln führen (methioninreich: 27,32 ± 2,80 µmol/l; homocystinreich: 40,61 ± 2,22 µmol/l). Als Vergleichsparameter zur Beurteilung pathophysiologischer Veränderungen diente zum einen der Gewebsgehalt an Homocystein, zum anderen wurden die intrazellulären Konzentrationen von S-Adenosyl-Methionin (SAM) und S-Adenosyl-Homocystein (SAH) betrachtet. Es zeigten sich besonders in Leber und Niere signifikante Unterschiede zwischen einer methioninreichen und einer homocystinreichen Diät bei Ratten. Dies ist eine mögliche Erklärung dafür, dass die bei vierwöchiger methioninreicher Diät gefundenen Ergebnisse nicht mit Literaturdaten übereinstimmen. Abschließend wurde der Frage nachgegangen, ob eine homocytinreiche Ernährung, wie in der vorherigen Studie angewandt, überhaupt möglich ist. Da zwar die Gehalte von Methionin in fast allen Lebensmitteln bekannt sind, nicht aber die von Homocystein, wurde untersucht, in welchen Konzentrationen Homocystein in Lebensmitteln enthalten ist. In Schwarzbier (0,03 mg/l), Weißbrot (0,95 mg/kg), Roquefort-Käse (0,50 mg/kg), Thunfisch (0,25 mg/kg) und Schweineleber (0,31 mg/kg) konnte Homocystein bestimmt werden. Da die Homocysteinkonzentrationen in diesen Beispiellebensmitteln mindestens um den Faktor 105 geringer waren als die Methioninkonzentrationen ist ein Einfluss von alimentärem Homocystein auf den Plasmaspiegel sehr unwahrscheinlich. Es wurde weiterhin geprüft, ob durch Darmbakterien ein Teil des alimentär aufgenommenen Methionins bereits im Dünndarm in Homocyt(e)in umgewandelt werden könnte. Dabei wurde eine vermehrte Homocysteinproduktion nach Methionin-Zugabe zu Dünndarmisolaten gefunden. Quantitativ kommt dieser Homocysteinquelle eine untergeordnete Bedeutung zu.
4
Reck, Andreas Michael [Verfasser], and Friedrich [Akademischer Betreuer] Schmahl. "Homocysteinstoffwechsel und Atherosklerose : Methionin-Belastungstests und langfristige Methionin-Applikation im Kaninchenmodell / Andreas Michael Reck ; Betreuer: Friedrich Schmahl." Tübingen : Universitätsbibliothek Tübingen, 2006. http://d-nb.info/1160754365/34.
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5
Mikulíková, Renata. "Studium vybraných typů sirných látek v pivu a pivovarských surovinách." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2010. http://www.nusl.cz/ntk/nusl-233307.
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Much attention has been recently devoted to sensorially active substances affecting beer quality in the Czech Republic and worldwide. Among them, the heterocyclic and sulphur containing compounds play an important role, some of them with high sensorial activity even in extremely low concentrations. Trace amounts of these compounds, which can be frequently found in foods, participate in formation of their aroma and this effect can be generally evaluated as favorable However, in malt or beer it is true only to a limited extent and the presence of heterocyclic and sulphur containing compounds are in this respect assessed rather unfavorably. The aim of the present study was to provide a survey about of problems in the field of sulphur containing compounds in barley, malt and beer, to describe metabolic paths leading to their formation and to verify experimentally possibilities of their determination using modern analytical methods. Sulphur-containing amino acids are a natural part of barley, malt and beer and are precursors of the origin of volatile sulphur substances. The most frequently occurring sulphur amino acids, metionine, cysteine and homocysteine, were selected for analytical monitoring. The method of gas chromatography was used to determine sulphur-containing amino acids in barley, malt and beer. Prior to the analysis, sulphur-containing amino acids were derived and volatile N(O,S)-ethoxycarbonyl propyl esters were formed; they were subsequently analyzed using the gas chromatography with mass detector (GC/ MSD) and the gas chromatography with flame photo detector (GC/ FPD). Direct analysis of sulphur volatile substances is possible only rarely as they are found in the analyzed matrices (malt, beer) only in very low concentrations ( g/kg,l - ng/kg,l). Before the analysis, the analytes must be extracted from the matrix and concentrated. The modern analytical methods SPME (Solid Phase Micro Extraction), SPDE (Solid Phase Dynamic Extraction) and TDAS (Thermal Desorption Autosampler) were experimentally compared for the extraction and subsequent concentration of sulphur volatile substances. The method of gas chromatography with flame photo detector was used to determine sulphur volatile substances. Following volatile sulphur substances were monitored: dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide, carbon disulphide, ethyl sulphide, diethyl disulphide, methionol, 3-methylthiophen, ethyl thioacetate, 2-methyl-1-buthanthiol. Only metionine was detected in significant amounts in the barley samples analyzed. Not only content but also dependence on a variety and locality were studied. Further, changes in methionine, cysteine and PDMS content during malting were followed. Results proved a significant decline in these substances content depending on the kilning temperature. Three types of fibers were tested for the analyses of the selected volatile sulphur substances in beer in the SPME method. PEG - a fiber with stationary phase Carbowax, PDMS - a fiber with stationary phase polydimethylsiloxan and a combined fiber CAR/PDMS - Carboxen and polydimethylsiloxan. Carbon disulphide, methionol, dimethyl sulphide, 3-methylthiophen and diethyl disulphide were detected with this method. Content of the other analyzed volatile sulphur substances was below the limit of detection. Further was tested usage the SPDE and TDAS methods. Both methods appear to be the suitable for the determination of volatile sulphur substances in beer.
6
Hohage, Oliver. "Makrochelatbildung und sequenzabhängige Spaltung bei den Reaktionen von Cisplatin mit methionin- und cysteinhaltigen Peptiden." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983533946.
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Mohrmann, Sarah [Verfasser]. "Experimentelle Untersuchungen zur Wirkung von Methionin auf den antioxidativen Status beim Broiler / Sarah Mohrmann." Gießen : Universitätsbibliothek, 2019. http://d-nb.info/1185976868/34.
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Schütz, Verena [Verfasser], and Elmar [Akademischer Betreuer] Heinzle. "Metabolic Engineering von Corynebacterium glutamicum zur Produktion von Methionin / Verena Schütz. Betreuer: Elmar Heinzle." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2010. http://d-nb.info/1050940962/34.
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9
Hüben, Michael. "Synthese von S-Adenosyl-L-methionin-Analoga für enzymatische DNA-Markierung und funktionelle Proteomuntersuchungen /." Aachen : Mainz, 2009. http://d-nb.info/996996257/04.
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Selzer, Paul M. "Charakterisierung und Untersuchung der Regulierung der S-Adenosyl-L-Methionin Decarboxylase von Trypanosoma brucei /." [S.l. : s.n.], 1994. http://www.gbv.de/dms/bs/toc/171353293.pdf.
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Lorenz, Antje. "In vivo-Analyse der hepatischen mitochondrialen Funktion HIV-infizierter Patienten durch den 13C-Methionin-Atemtest." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-96344.
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12
Mustafi, Nurije [Verfasser]. "Die Entwicklung und Anwendung eines Einzelzell-Biosensors zur Detektion von L-Methionin und den verzweigtkettigen Aminosäuren / Nurije Mustafi." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2013. http://d-nb.info/1043040943/34.
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Kröger, Thomas [Verfasser]. "Doppelt-aktivierte S-Adenosyl-L-Methionin-Analoga mit funktionalisierten Seitenketten zur sequenzspezifischen Übertragung durch DNA-Methyltransferasen / Thomas Kröger." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1031109323/34.
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Wiedenmann, Nicole. "Integration der 11C-Methionin-Positronenemissionstomographie in die stereotaktische Bestrahlungsplanung von Hirntumoren Validierung einer Methode zur automatischen Bildfusion multimodaler Datensätze /." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972579370.
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Martin, Julia [Verfasser], Arne [Akademischer Betreuer] Skerra, Wolfgang [Gutachter] Liebl, and Arne [Gutachter] Skerra. "Synthese von L-Methionin durch biokatalytische Fixierung von CO2 / Julia Martin ; Gutachter: Wolfgang Liebl, Arne Skerra ; Betreuer: Arne Skerra." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1220322458/34.
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Strunck, Anna-Carina. "Studien über die Aktivierung der Phospholipasen in N-Formyl-Methionin-Leucin-Phenylalanin stimulierten humanen neutrophilen Granulozyten Dissoziation zwischen Arachidonsäurefreisetzung und Leukotrien B4-Synthese = Studies of the activation of phospholipases in N-formyl-methionyl-leucyl-phenylalanine stimulated human neutrophils /." [S.l.] : [s.n.], 2003. http://www.diss.fu-berlin.de/2003/186/index.html.
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Stöber, Barbara. "Charakterisierung des Transportes der Aminosäuren L-[Methyl-3H]-Methionin (Met) und O-(2-[18F]fluorethyl)-L-Tyrosin (FET) in humane Lymphozyten, Makrophagen und Kolonkarzinomzellen." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973390352.
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HIREL, PH HERVE. "Specificite de la methionyl-aminopeptidase : etude systematique in vivo de l'excision de la methionine amino-terminale des proteines de escherichia coli." Palaiseau, École polytechnique, 1990. http://www.theses.fr/1990EPXX0007.
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Environ 40% des proteines solubles d'escherichia coli ont conserve, sous leur forme mature, leur methionine amino-terminale. D'une analyse informatique des sequences n-terminales de proteines d'e. Coli, nous avons pu induire un modele enzymatique base sur la reconnaissance de la taille du second acide amine, rendant compte de l'occurrence (ou de la non occurrence) de la maturation, et compatible avec l'existence d'une enzyme unique. Dans le but de valider et preciser notre modele, nous avons systematiquement modifie, par mutagenese dirigee, le second codon du gene de la methionyl-arnt synthetase, fusionne a celui de la beta-galactosidase. Les 20 variants de la proteine hybride ont ete purifies et leur sequence n-terminale determinee. Les resultats sont en parfait accord avec le modele propose, et confirment meme ses predictions concernant des acides amines non encore rencontres en seconde position d'une proteine d'e. Coli. Notre modele affine prevoit que l'espece proteique majoritaire correspondra a une excision de la methionine n-terminale, si et seulement si la longueur de la chaine laterale du second acide amine est inferieure a une valeur seuil comprise entre 2,83 angstroms (cysteine) et 3,68 angstroms (asparagine). Des resultats recents sur la demi-vie des proteines comme fonction de leur acide amine n-terminal suggerent qu'un role possible de la methionine-aminopeptidase servit a participer au controle de la stabilite des proteines. Une autre hypothese, proposant que la map permette un recyclage de la methionine servant au demarrage de traduction, est discutee
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Blum, Nicole Michaela [Verfasser], G. [Akademischer Betreuer] Stangl, K. [Akademischer Betreuer] Eder, and A. [Akademischer Betreuer] Müller. "Einfluss von Selen auf ausgewählte Funktionen des Intermediärstoffwechsels und die differenzielle Regulation von Phase-II-Enzymen sowie die antagonistische und synergistische Wirkung von Methionin und Glucoraphanin auf diese Prozesse : [kumulative Dissertation] / Nicole Michaela Blum. Betreuer: G. Stangl ; K. Eder ; A. Müller." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2014. http://d-nb.info/1052221106/34.
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DESPONS, LAURENCE. "Reconnaissance de l'arn de transfert methionine par la methionyl-arnt synthetase de levure : une analyse fonctionnelle des determinants d'identite de la proteine et de l'acide nucleique." Université Louis Pasteur (Strasbourg) (1971-2008), 1993. http://www.theses.fr/1993STR13029.
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La methionyl-arnt synthetase (metrs) de levure est un monomere de 85000 daltons possedant une forte homologie de sequence primaire avec la metrs native d'e. Coli. Le cur catalytique de l'enzyme de levure comprend les residus 192-594 et possede les memes caracteristiques qu'un fragment trypsique actif de la metrs d'e. Coli dont la structure 3-d a pu etre resolue: l'extremite c-terminale etablit avec le domaine n-terminal un lien essentiel au maintien d'une conformation active et stable de l'enzyme, comme l'ont montre des etudes de deletions progressives de l'extremite c-terminale des deux molecules. La metrs de levure est une metalloenzyme a zinc. Le zinc joue un role structural important. Les resultats d'une analyse par mutagenese dirigee montrent que les cysteines 350, 353 et 367 et l'acide aspartique 370 du motif doigt de zinc c-x#2-c-x#1#3-c-x#2d, present dans le domaine d-terminal, sont essentiels a l'activite et la stabilite de l'enzyme. Nous n'avons cependant pas pu mettre en evidence une perte de fixation du zinc, quand les cysteines 350 et 353 sont simultanement remplacees par des alanines. Les elements d'identite de l'arnt#m#e#t ont ete definis grace a la possibilite de creer des arnt synthetiques par une methode de transcription in vitro. Il ressort de ce travail que l'anticodon cau est incapable a lui seul de conferer une identite methionine a un arnt: il faut soit une boucle anticodon cucauaa, soit une combinaison de l'anticodon cau et de la base discriminatrice a73. Nous avons verifie, par mutagenese dirigee, un modele structural du complexe enzyme-arnt. Cette analyse fait apparaitre deux regions de la metrs impliquees dans la reconnaissance specifique de l'anticodon cau. Le peptide 650-663 et notamment la leucine 658 interviendrait surtout lors de la formation du complexe initial. Des residus, dans la region conservee 582-588, apparaissent comme les elements proteiques les plus critiques pour la selection positive de l'arnt#m#e#t et interviendraient au niveau de l'etat de transition
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Ayer, Carol Theresa. "Methionine Metabolism in Fasciola Hepatica." PDXScholar, 1990. https://pdxscholar.library.pdx.edu/open_access_etds/3954.
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5'-Deoxy-5'-methylthioadenosine (MTA) is derived from s-adenosylmethionine (AdoMet) during the synthesis of the polyamines spermidine and spermine. Methionine can be regenerated from MTA by one of two mechanisms. In mammalian cells and some microorganisms, MTA is degraded to adenine and 5-methylthioribose-1-phosphate (MTR-1-P) via MTA phosphorylase. In certain other microbes, however, MTA is catabolized in two steps; first to adenine and 5-methylthioribose (MTR) via MTA nucleosidase followed by conversion of MTR to MTR-1-P via MTR kinase.
This study was to demonstrate the presence of MTA nucleosidase or MTA phosphorylase in both redia containing cercariae and adult Fasciola hepatica Linnaeus, 1758. If MTA nucleosidase was present, it was wanted to determine if MTR kinase was also present.
The phosphate-dependent cleaving activity of MTA phosphorylase was demonstrated in the cell-free extracts of adult Fasciola hepatica along with an unidentified MTR metabolizing activity. Redia containing cercariae showed MTA nucleosidase and MTR kinase activity.
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Wong, Chi-wai Bonnie. "Essentiality of methionine aminopeptidase in staphylococcus aureus." Thesis, Click to view the E-thesis via HKUTO, 2004. http://sunzi.lib.hku.hk/hkuto/record/B31479212.
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Chu, Jhih-Wei 1973. "Oxidation of methionine residues in protein pharmaceuticals." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28660.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004.<br>Includes bibliographical references (p. 171-189).<br>(cont.) of free methionine. Therefore, the environments surrounding different methionine sites in G-CSF mainly provide spatial restriction to the access to the solvent but do not affect oxidation in a specific manner, consistent with the good correlation between 2SWCN's and the rates of oxidation. A comprehensive picture of oxidation is thus developed. It allows an accurate prediction of protein oxidation, and provides a rationale for developing strategies to control oxidation, such as modulating protein conformation via adding excipients. This knowledge could aid in developing in a more rational manner solvent formulations that protect therapeutic proteins against oxidation.<br>Oxidation of the amino acid methionine by peroxides in aqueous formulations of proteins is a critical issue in the development of therapeutic products. It must be controlled so that therapeutic proteins can maintain their activity. In addition, oxidized therapeutics are undesirable due to their possible immunogenetic effects. An understanding of the mechanism and the factors that influence the reactivity of different methionine sites toward oxidation is therefore important. In this thesis, computational methods are applied and developed to address these problems. First, a mechanism by which peroxides oxidize the sulfur atom of methionine is developed. The rate-limiting step was found to be the breaking of the O-O bond of H₂O₂ and the formation of the S-O bond during which significant charge separation is developed. The charge separation can be stabilized via specific interactions such as hydrogen bonding with surrounding water molecules. This "water-mediated" mechanism of oxidation is consistent with experimental data such as those on activation energies of oxidation and pH dependence of the rates of oxidation. Based on the "water-mediated" mechanism, a structural property, average 2-shell water coordination number (2SWCN), has been shown to correlate well to the rates of oxidation of different methionine groups in Granulocyte Colony-Stimulating Factor (G-CSF) and in a Human Parathyroid hormone fragment (hPTH(1-34)). Including the dynamics of protein and water molecules in an explicit manner was found to be important for such correlation. Via combined quantum mechanical and molecular mechanical free energy simulations, the activation free energies of the oxidation of methionine residues in G-CSF are found to be equivalent to the values for the oxidation<br>by Jhih-Wei Chu.<br>Ph.D.
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POIRSON, BICHAT FLORENCE. "Analogues de methionine associes a une carence en methionine : pharmacologie et therapeutique experimentale dans les tumeurs solides de l'homme." Paris 6, 1997. http://www.theses.fr/1997PA066757.
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L'elaboration du concept therapeutique propose repose sur les differences entre le metabolisme de la methionine du tissu cancereux et celui du tissu normal. Cette deviation metabolique est liee principalement aux pertes des chromosomes 9 et 10, porteurs des genes codant des enzymes intervenant dans le metabolisme de la methionine. Ces alterations existent dans de nombreuses tumeurs dont celle des gliomes et des tumeurs prostatiques. In vitro, en cultivant les cellules dans un milieu sans methionine avec homocysteine (met hcy +), nous avons mis en evidence que de nombreuses lignees cellulaires tumorales sont dependantes en methionine exogene. Differents analogues de la methionine ont ete testes en milieu met hcy +, afin de potentialiser l'effet de la privation en methionine. L'hypothese etait que la metabolisation de ces analogues conduirait a la formation de metabolites inactifs ou toxiques. Les resultats montrent : un blocage irreversible des cellules en phase s ; l'induction d'une mort cellulaire par apoptose ; une reduction rapide et importante de la quantite d'atp ; une diminution rapide de methionine intracellulaire, confirmant la dependance en methionine des cellules tumorales ; une incorporation elevee de l'ethionine dans les cellules ; une utilisation de l'homocysteine exogene dans la voie de transulfuration. In vivo, un effet antitumoral significatif de l'association regime met hcy +-ethionine a ete obtenu en particulier, dans le cas de tumeurs gliales, greffees sur souris nude. La mesure de la distribution tissulaire de la methionine, de l'ethionine et de l'homocysteine (par cg-sm) a montre que : la methionine a un tropisme important pour la tumeur ; l'ethionine passe la barriere hematoencephalique et est trois fois plus incorporee dans la tumeur que dans les autres organes. Un nouveau modele de tumeur humaine de la prostate hormono-dependante chez la souris nude, a ete etabli et caracterise. Une potentialisation importante de l'effet antitumoral induit par une molecule de chimiotherapie (doxorubicine, cisplatine, fluoro-5 uracile) associe au regime carence en methionine-ethionine a ete obtenue. Ainsi, la carence en methionine obtenue par le regime met hcy + associe a un analogue, offre de nouveaux outils therapeutiques, dans le traitement des cancers avances chimioresistants de l'homme.
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Plank, Johanna E. "Methionine and Methionine Analog Supplementation: Comparison of Bioavailability In Dairy Cows and Differential Utilization by Rumen Microbes in Batch Culture." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306946206.
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Kocic, Vesna Garovic. "Methionine auxotrophy in inborn errors of cobalamin metabolism." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56756.
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Several of the inborn errors of vitamin B$ sb{12}$ (cobalamin, Cbl) metabolism (cblC, cblD, cblE, cblF, cblG) are associated with homocystinuria and hypomethioninemia due to a functional deficiency of the cytoplasmic enzyme methionine synthase which requires methylcobalamin (MeCbl) as a cofactor. We compared the growth of cultured fibroblasts from controls with those from patients with a selective deficiency of MeCbl (cblE and cblG) and with those from patients with a defect in both MeCbl and adenosylcobalamin (AdoCbl) (cblC, cblD and cblF). Cells were grown in methionine and folic acid free media and in fully supplemented medium. Control cells were able to grow in the deficient medium supplied with homocysteine, cobalamin and folate, while mutant cells were not, due to their inability to synthesize methionine from its immediate metabolic precursor, homocysteine. This differential growth is useful for screening for genetic defects of methionine biosynthesis. Moreover, by correcting methionine auxotrophy in these cells, it may be possible to isolate genes which code for the products that are deficient in these disorders.
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Lim, Jina. "EVALUATION OF L-METHIONINE BIOAVAILABILITY IN NURSERY PIGS." UKnowledge, 2015. http://uknowledge.uky.edu/animalsci_etds/54.
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DL-Methionine (Met) has been conventionally used in swine diets with assumption of similar bioefficacy with L-Met. However, because L-Met is the form that is utilized by animals for protein synthesis, L-Met could, theoretically, be more available. Four experiments were conducted to evaluate L-Met bioavailability in nursery pigs with 21-day growth trials. A total of 105,105,112 and 84 crossbred pigs were used in Exp. 1, 2, 3 and 4, respectively. Each experiment had a low Met basal diet and 3 levels of the Met sources (DL-Met and L-Met). In addition to the basal diet, supplementation levels were 0.053%, 0.107% and 0.160% in Exp. 1, 0.040%, 0.080% and 0.120% in Exp. 2, 0.033%, 0.067% and 0.100% in Exp.3, 0.040%, 0.080% and 0.120% in Exp. 4. Body weight (BW), average daily gain (ADG), average daily feed intake (ADFI), gain: feed (G:F) were measured and plasma urea nitrogen (PUN) was analyzed in blood samples weekly. In Exp. 3 and 4, preference studies were conducted with the basal diet and the second highest level of each Met source. When additional DL-Met or L-Met were supplemented to the basal diet, BW, ADG, ADFI, and G:F ratio increased (P < 0.05). In the comparison between the DL-Met and L-Met diets in Exp. 1, pigs in the L-Met group had greater ADG and G:F ratios in the d 0-7 (P < 0.05) period than those in the DL-Met group. However, there were no differences for the overall experimental period. In Exp. 2, pigs in the DL-Met group had greater BW (P < 0.05), ADG (P < 0.05) and ADFI (P < 0.05) than those in the L-Met group for the overall period whereas no differences were observed in G:F ratios and PUN concentrations. In Exp. 3 and 4, there were no differences in BW, ADG, ADFI, G:F ratios or PUN concentrations between L-Met and DL-Met groups for the overall period. There was no preference exhibited for either the DL-Met or L-Met diet. In the results of relative bioavailability of L-Met to DL-Met, the values was 111.1% for d 0-14 based on the estimation by ADG in Exp. 1; L-Met bioavailability was lower than DL-Met based on all response measures in Exp. 2. However, in Exp. 3, relative bioavailability of L-Met to DL-Met was 100.4, 147.3, and 104.1% for d 0-14 ADG, G:F ratio and PUN concentrations. In Exp 4, the relative bioavailability of L-Met was 92.9, 139.4 and 70.4% for d 0-14 ADG, G:F ratio and PUN concentrations. In conclusion, using L-Met in the nursery diet demonstrated no consistent beneficial effect on ADG, G:F ratio or relative bioavailability compared to conventional DL-Met.
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Ferrier, L. J. "The methionine and cystine requirements of growing pigs." Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383688.
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Cadirci, Sahin. "Feeding methionine to laying hens in drinking water." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368557.
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Zarrilli, Hugo Alfredo Humberto Lago. "Folding and assembly of the methionine repressor protein." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310129.
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Wilson, Fiona A. "The methionine cycle and pregnancy in the rat." Thesis, University of Aberdeen, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430233.
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This study aims to identify in the non-pregnant rat and pregnant dam those tissues with the greatest methionine cycle activity and those that are most sensitive to methyl group deficiency. In addition, as human studies rely heavily on the plasma measurements, this study also aims to investigate whether plasma metabolites of homocysteine and methionine reflect tissue metabolism. This study investigated the kinetics of methionine metabolism in the rat using an L-[1-<sup>13</sup>C, <sup>2</sup>H<sub>3</sub>] methionine tracer that is converted to [1-<sup>13</sup>C] homocysteine and [1-<sup>13</sup>C] methionine by passage through the methionine cycle. The effect of the methionine, folate and choline content in the diet was studied by measuring the conversion of homocysteine to methionine within tissue of the pregnant and non-pregnant rat. Tissue homocysteine methylation was estimated from the ratio of [1-<sup>13</sup>C] methionine to [1-<sup>13</sup>C, <sup>2</sup>H<sub>3</sub>] methionine in comparison with the same ratio in the plasma. The main findings of this study were that the liver and the pancreas were the main sites of homocysteine methylation within the rat, with the pancreas also emerging as the major contributor to plasma homocysteine and synthesised methionine. Additionally, it was observed that ht e fetus was able to compensate for a reduction in homocysteine methylation as a consequence of folate and choline deficiency within the dam until day 19 of gestation. After this time, however, the fetus cannot increase the conversion of homocysteine to methionine to compensate. This study also indicated that as gestation progresses maternal methionine synthesis was reduced to conserve folate and choline for use within the fetus.
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Murray, Ben. "Structural and functional studies of human methionine adenosyltransferases." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2046880/.
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S-Adenosylmethionine (SAMe) is the principal methyl donor of the cell and is synthesized via an ATP-driven process by methionine adenosyltransferase (MAT) enzymes. It is tightly linked with cell proliferation in liver and colon cancer. In humans, there are three genes, MAT1A, MAT2A and MAT2B, which encode MAT enzymes. MAT2A and MAT2B transcribe MATα2 and MATβ enzyme subunits, respectively, with catalytic and regulatory roles. The MATα2β complex is expressed in nearly all tissues and is thought to be essential in providing the necessary SAMe flux for methylation of DNA and various proteins including histones. In human hepatocellular carcinoma MAT2A and MAT2B genes are upregulated, highlighting the importance of the MATα2β complex in liver disease. The individual subunits have been structurally characterized but the nature of the complex has remained elusive despite its existence having been postulated for more than 20 years and the observation that MATβ is often co-localized with MATα2. Though SAMe can be produced by MAT(α2)4 alone, this thesis shows that the kcat of the MATα2β complex is three- to four fold higher depending on the variants of MAT that participate in complex formation. Using X-ray crystallography and solution Xray scattering, the first structures are provided of this 258 kDa functional complex both in crystals and solution with an unexpected stoichiometry of 4α2 and 2βV2 subunits. It is demonstrated that the N-terminal regulates the activity of the complex and it is shown that complex formation takes place surprisingly via the C-terminal of MATβV2 that buries itself in a tunnel created at the interface of the MAT(α2)2. The structural data suggest a unique mechanism of regulation and provide a gateway for structure-based drug design in anticancer therapies. ii Crystal structures of human MATα2 containing various bound ligands providing a ‘structural movie’ of the catalytic steps are also presented. High to atomic-resolution structures reveal the structural elements of the enzyme involved in the utilization of substrates, methionine and adenosine, and the formation of the product SAMe. MAT enzymes are also able to produce S-adenosylethionine (SAE) from substrate ethionine. Ethionine, an S-ethyl analogue of the amino acid methionine, is known to induce steatosis and pancreatitis. It is shown here that S-adenosylethionine occupies the active site in a manner similar to SAMe, confirming that ethionine also binds and utilizes the same catalytic site to form the product SAE. Through by gel filtration and small angle x-ray scattering (SAXS) it is shown that the catalytic MAT enzymes exist in multiple oligomeric populations in solution, whilst the regulatory MAT subunit, MATβ, is monomeric. In view of these data and recent crystallographic structures of the MAT enzyme complex, a rationalization of nomenclature for the MAT enzymes and their complexes has been produced.
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Zhang, Ping. "Dynamics of methionine ligand rebinding in cytochrome c." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12899.
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Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.<br>Geminate recombination of the methionine ligand to heme iron in ferrous cytochrome c protein following photodissociation displays rich kinetics. It is of particular interest to develop an understanding of fast and slow rebinding timescales, observed in experimental studies, in terms of features of the protein's underlying energy landscape. To accurately model this complex molecular system, the classical empirical force field for the protein and solvent has been extended by incorporating information from ab initio potential energy surface calculations. An algorithm based on the Landau-Zener non-adiabatic transition theory has been developed and implemented into an otherwise classical molecular dynamics simulation model to allow for electronic surface hopping between the singlet and the quintet states, critical to the dissociation and rebinding transitions. Multiple conformational substates of the dissociated methionine are found to participate in the reaction dynamics. Varying timescales for the experimentally observed fast and slow ligand rebinding are elucidated through a mechanism based on the underlying dynamics of interconversion between conformational substates. A two-dimensional reaction coordinate that captures the essential protein dynamics is proposed.
Temperature and solvent dependence of the methionine ligand rebinding in cytochrome c has been studied. Conformational substates of methionine, observed at high temperature and found to be critical to the high temperature rebinding dynamics, are not observed during the process of dissociation and rebinding at low temperature or in high viscosity conditions. The activation energy for transitions between substates is estimated through its temperature dependence. A higher energetic barrier at lower temperature leads to a lower reaction rate. The distinctive rebinding kinetics and the reaction paths at low temperature suggest that the rebinding dynamics are dictated by the conformational substates accessible to the protein prior to photodissociation. The more single-exponential like nature of the kinetics at higher temperature is attributed to the protein conformational homogeneity. Insight into the reaction dynamics derived from these simulations has led to suggestions for future experiments to further probe the role of dynamic heterogeneity in the kinetics of function-related ligand-protein binding.
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Madeira, Jean-Paul. "Dynamique de l'exoprotéome et homéostasie rédox chez Bacillus cereus : rôle de l'oxydation et réduction des résidus méthionines." Thesis, Avignon, 2016. http://www.theses.fr/2016AVIG0336/document.
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Bacillus cereus est une bactérie aéro-anaérobie facultative à Gram positif ubiquiste pouvant s’adapter à de nombreux environnements et s’y développer. C’est un agent pathogène de l’homme capable de produire tout un éventail de protéines extracellulaires et de toxines jouant un rôle majeur dans la pathogénicité de ce micro-organisme. B. cereus croit suivant un métabolisme de type respiratoire en aérobiose et fermentaire en anaérobiose en l’absence d’accepteur final d’électrons. En aérobiose, la chaine respiratoire est une source majeure des dérivés réactifs de l'oxygène (ROS) endogènes. En anaérobiose, les ROS endogènes sont générés en réponse au stress oxydant secondaire au stress nutritionnel et au stress réducteur, lorsque les cultures sont réalisées à bas potentiel d’oxydo-réduction (POR). Les résidus méthionines (Met) sont particulièrement sensibles à l’oxydation par les ROS. L’oxydation des Met conduit à la formation de méthionine sulfoxyde (Met(O)), un dérivé oxydé stable détectable par spectrométrie de masse (MS). L'oxydation des résidus Met est réversible : leur réduction est catalysée par des méthionines sulfoxyde réductases (Msr). Pour déterminer le rôle de l’oxydation des résidus Met, nous avons réalisé une étude exhaustive par MS de la dynamique de l’exoprotéome de la souche ATCC 14579 (pBClin 15) de B. cereus en aérobiose (pO2 = 100%) et en anaérobiose (pO2 = 0%) à haut (POR initial = +140 mV) et bas potentiel redox (PORi= -350 mV). Les résultats ont montré que la dynamique des toxines était représentative de la dynamique de l’exoprotéome à la fois en termes d’abondance relative de protéines et d’oxydation des Met dans les trois conditions testées. L’analyse des résultats suggèrent que (i) l’abondance des toxines et leur taux de méthionines oxydés reflètent le niveau d’oxydation cellulaire et (ii) la sécrétion de toxines au cours de la croissance cellulaire contribue au maintien de l'homéostasie redox intracellulaire en piégeant les ROS endogènes, en particulier en phase active de croissance en aérobiose et en fin de croissance en anaérobiose. Pour étayer l’hypothèse selon laquelle, les Met des protéines extracellulaires, et des toxines en particuliers sont des composants de la machinerie cellulaire antioxydante, nous avons construit une souche mutante ne synthétisant plus MsrAB et comparer le protéome et l’exoprotéome de cette souche mutante avec celle de la souche parentale en aérobiose et anaérobiose à haut POR. Cette étude a mis en évidence l’implication de MsrAB mais également du plasmide cryptique pBClin15 dans la sécrétion des toxines et le maintien de l'homéostasie redox intracellulaire<br>Bacillus cereus is a Gram-positive aerobic or facultative anaerobic worldwide-distributed bacterium. In addition, B. cereus is a human pathogen able to produce a range of extracellular enzymes and toxins playing a major role in the virulence of the bacteria. In presence of oxygen, B. cereus performs respiration. Without oxygen or other electron acceptors, it performs mixed-acid fermentation. Under aerobiosis, the respiratory electron transport chain is a major source of endogenous reactive oxygen species (ROS). Under anaerobiosis, endogenous ROS are generated in response to reductive stress (mainly under high-reductive anaerobiosis) and to starvation (nutrient stress), i.e. in response to secondary oxidative stresses. Methionine residues (Met) of proteins are vulnerable to oxidation by free radicals. Oxidation of Met leads to the formation of methionine sulfoxide (Met (O)), a stable by-product detectable by mass spectrometry (MS). Met(O) can be reduced back to Met by the action of methionine sulfoxide reductase (Msr). To determine the role of oxidation of Met residues, B. cereus exoproteome time courses were monitored by MS under low oxidation-reduction potential (ORP) anaerobiosis (initial ORP = +140 mV and pO2 = 0%), high-ORP anaerobiosis (iORP = -350 mV and pO2 = 0%), and aerobiosis (pO2 = 100%). The results indicated that toxin-related proteins were the most representative of the exoproteome changes, both in terms of protein abundance and their Met(O) content in the presence and in the absence of oxygen. The analysis results suggest that (i) the abundance of toxins and their oxidized methionines rates reflect the cellular oxidation level and (ii) the secretion of toxins during growth helps to maintain redox homeostasis by keeping endogenous ROS at bay, during the exponential growth phase under aerobic conditions and at the end of growth under anaerobiosis. To support our hypothesis that Met residues of extracellular proteins, particulars of toxins are components of the cellular machinery antioxidant, we constructed a mutant strain by deleting the gene of MsrAB and compare the cellular proteome and exoproteome of this mutant strain with the wild-type strain under aerobiosis and high-ORP anaerobiosis. This study highlighted the involvement of MsrAB but also pBClin15 plasmid in the secretion of toxins and maintain of the intracellular redox homeostasis
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Kang, Wenli. "Kinetic study of ammonium/ammonia production by Anabaena variabilis cultures in relation with a continuous gas stripping." Thesis, Nantes, 2016. http://www.theses.fr/2016NANT4041/document.
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Certaines cyanobactéries photoautotrophes sont capables de fixer l’azote atmosphérique grâce à des cellules spécialisées, les hétérocytes. De plus, en aérobiose, comme ces cellules peuvent excréter de l’ammonium lorsque leurs activités glutamine synthétase sont partiellement inhibées. Elles sont considérées comme usines cellulaires potentielles pour une bioproduction d’engrais azoté. Nous utilisons une souche mutante de Anabaena variabilis PCC 7937-C9, cyanobactérie hétérocytée à taux de croissance élevé, pour étudier la capacité à produire de l’ammonium en photobioréacteurs. Les caractéristiques de croissance de cette souche ne différent pas significativement de celles de la souche sauvage, avec un taux de croissance spécifique maximal de 3.0 j–1 à 30°C. Nous montrons qu’une partie de l’azote excrété dans le milieu de culture est entrainé sous forme de NH3 par la phase gazeuse, expliquant ainsi des sous-estimations antérieures. Cette production dépend de la température, l’irradiance, le taux d’aération et la concentration en MSX. Des études cinétiques confirment que la production d’azote ammoniacal en phase liquide et en phase gazeuse est corrélée aux variations de pH. Une régulation pulsée de pH permet d’accroitre la production de NH3. Des cultures en chemostat confirment que les productions de NH3 gazeux sont maximales à pH 8.8. Une variation cyclique des teneurs en NH4 +/NH3 dissous semble réguler les teneurs en NH4 +/NH3 en dessous d’un seuil critique de 1.5 mmol L–1 via une consommation par les cellules végétatives. Ces caractéristiques physiologiques sont analysées pour une application potentielle à la fourniture d’azote à des cultures de microalgues oléagineuses<br>Some photoautotrophic cyanobacteria species are able to fix dinitrogen thanks to specialized cells, the heterocyts. Moreover, these cells are known to secrete ammonia when the glutamine synthase activity is partially inhibited under aerobic conditions. They are considered as potential cell factories for fertilizer. The present study uses a mutant strain of Anabaena variabilis PCC 7937-C9, a fast-growing heterocytous cyanobacterium, to investigate the potential use of diazotrophic cyanobacteria in photobioreactors for ammonium production. The growth characteristics of this strain cultivated in chemostat cultures are not significantly different from those of the wild strain, with a maximal specific growth rate of 3.0 d–1 at 30°C. A part of the combined nitrogen excreted in the culture medium is shown to be stripped through the aeration of the cultures as NH3, indicating previous underestimation of NH4 +/NH3 excretion. This process is shown to be affected by parameters such as temperature, irradiance, gas flow rate and MSX concentrations. Kinetics study reveals that the dissolved NH4 +/NH3 as well as the gaseous NH3 productions are correlated to pH variations production; a pulse regulation of pH is used to increase the NH3 production. Chemostat cultures with pH regulation are used to confirm that maximal gaseous NH3 is produced at pH 8.8. A cyclic variation of dissolved NH4 +/NH3 seems to regulate the NH4 +/NH3 concentrations under a threshold level of 1.5 mmol L–1; uptake of NH4 + by vegetative cells seems to be involved. These physiological features are discussed in view of operative conditions for efficient nitrogen supply for production by oleaginous microalgae
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Sillaots, Susan L. (Susan Linda). "Heterogeneity in cblG : differential binding of vitamin B12 to methionine synthase." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60091.
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Fibroblasts from patients with functional methionine synthase deficiency can be divided into 2 complementation classes, cblE and cblG. Both have low levels of intracellular methylcobalamin. Both groups also demonstrate low levels of incorporation of label from 5-methyltetrahydrofolate into macromolecules. Under standard reducing conditions, methionine synthase specific activity is normal in cblE fibroblast extracts, but is low in cblG fibroblast extracts. Seven cblE and seven out of ten cblG cell lines demonstrate levels of accumulation of ($ sp{57}$Co) CN-Cbl in fibroblasts comparable to that of control cells. They exhibit similar proportions of label associated with the two intracellular cobalamin binders, methylmalonyl-CoA mutase and methionine synthase. The remaining three cblG cell lines exhibit a lower level of cobalamin accumulation, and demonstrate a lack of cobalamin association with the enzyme methionine synthase. The specific activity of methionine synthase is almost undetectable in the three cblG cell lines that showed no such association. These results demonstrate heterogeneity within the cblG group and suggest that the defect in cblG affects the methionine synthase apoenzyme.
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Ng, Wai-yun Louisa. "Bacterial methionine aminopeptidase as a potential target for therapeutics." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38761233.
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Ng, Wai-yun Louisa, and 吳慧欣. "Bacterial methionine aminopeptidase as a potential target for therapeutics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38761233.
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Simmons, Alfred Lincoln Arthur. "Dietary methionine requirement of juvenile arctic charr, Salvelinus alpinus." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ27544.pdf.
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Wenninger, Elizabeth A. "The design and synthesis of inhibitors of methionine synthase." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246140.
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Bonissone, Stefano Romoli. "Exploration of N-terminal methionine excision via comparative proteogenomics." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p1474117.
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Thesis (M.S.)--University of California, San Diego, 2010.<br>Title from first page of PDF file (viewed February 19, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 45-48).
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Lou, Xiao. "Biochemical and structural studies of human methionine synthase reductase." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/biochemical-and-structural-studies-of-human-methionine-synthase-reductase(822952fc-8bef-4a30-9221-7fb154638193).html.
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Human methionine synthase reductase (MSR) is a 78-kDa diflavin enzyme involved in folate and methionine metabolism. It regenerates the cofactor of methionine synthase (MS), cob(II), to reduce inactive MS. MSR and one of its the FAD/NADPH binding domain were cloned as GST-tagged fusion proteins for expression and purification in Escherichia coli. And a 1.9 Å Crystals of the FAD/NADPH binding domain of MSR with and without NADP+ were produced and carried out X-ray diffraction experiment and the structure of the crystal was solved by molecule replacement method. The activation domain of human MS was also expressed and purified in Escherichia coli and crystallization conditions determined. A new expression vector for full-length MSR, which contains a N-terminal GST tag, and C-terminal 6× His tag, was constructed and validated by sequencing, restriction enzymes digestion and successfully expressed in E. coli and Yeast Pichia pastoris. Based on the structure information, site-directed mutagenesis on the two positions Asp652 and trpytophan697 of MSR were designed and completed. The variants D652A, D652R, D652N of the FAD/NADPH binding domain of MSR and the variants D652A,D652R,D652N, W696A,W697H of the full-length MSR were cloned and expressed in BL21 (E. coli). The proteins of these mutants were purified by affinity chromatography, anion exchange chromatography and gel filtration chromatography. And the kinetic studies on these variants of MSR were investigated in steady state kinetic study, steady state inhibition studies, stopped-flow pre steady-state kinetic and redox potential studies. Compared with the data of the wild type MSR, the turnover number of variants all decreased, the catalytic ability become lower and the midpoint potential of cofactor FAD occurred positive shift. Both 2'5-ADP and NADP+ were competitive inhibitors for variants of MSR. However, 2'5'-ADP was relative strong inhibitor than NADP+. All the data on variants of MSR suggested the Asp652 and tryptophan697 were two important structural and function determinant of MSR. To investigate the dynamic properties of EPR, ENDOR and ESMME are used to investigate the existence of the semiquinone flavin cofactors, FAD and FMN, and the hyperfine coupling arising from the interaction of some nuclei with the unpaired electron spin. ELDOR spectroscopy was applied to measure the distance between the FAD and FMN in MSR under the binding of 2', 5'-ADP, NADP and the activation domain of MS to further check the conformational change of MSR.
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Gao, Chao. "HOMOCYSTEINE-METHIONINE CYCLE IS A KEY METABOLIC SENSOR SYSTEM CONTROLLING METHYLATION-REGULATED PATHOLOGICAL SIGNALING - CD40 IS A PROTOTYPIC HOMOCYSTEINE-METHIONINE CYCLE REGULATED MASTER GENE." Master's thesis, Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/603000.
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Biomedical Sciences<br>M.S.<br>Homocysteine-Methionine (HM) cycle produces a universal methyl group donor S-adenosylmethionine (SAM), a competitive methylation inhibitor S-adenosylhomocysteine (SAH), and an intermediate amino acid product homocysteine (Hcy). Elevated plasma levels of Hcy is termed as hyperhomocycteinemia (HHcy) which is an established risk factor for cardiovascular disease (CVD) and neural degenerative disease. We were the first to describe methylation inhibition as a mediating biochemical mechanism for endothelial injury and inflammatory monocyte differentiation in HHcy-related CVD and diabetes. We proposed metabolism-associated danger signal (MADS) recognition as a novel mechanism for metabolic risk factor-induced inflammatory responses, independent from pattern recognition receptor (PRR)-mediated pathogen-associated molecular pattern (PAMP)/danger-associated molecular pattern (DAMP) recognition. In this study, we examined the relationship of HM cycle gene expression with methylation regulation in human disease. We selected 115 genes in the extended HM cycle, including 31 metabolic enzymes and 84 methyltransferases (MT), examined their mRNA levels in 35 human disease conditions using a set of public databases. We discovered that: 1) HM cycle senses metabolic risk factor and controls SAM/SAH-dependent methylation. 2) Most of metabolic enzymes in HM cycle (8/11) are located in cytosol, while most of the SAM-dependent MTs (61/84) are located in the nucleus, and Hcy metabolism is absent in the nucleus. 3) 11 up-regulated, 3 down-regulated and 24 differentially regulated SAM/SAH-responsive signal pathways are involved in 7 human disease categories. 4) 8 SAM/SAH-responsive H3/H4 hypomethylation sites are identified in 8 disease conditions. We conclude that HM cycle is a key metabolic sensor system which mediates receptor-independent MADS recognition and modulates SAM/SAH-dependent methylation in human disease. We propose that HM metabolism takes place in cytosol and that nuclear methylation equilibration requires nuclear-cytosol transfer of SAM, SAH and Hcy. CD40 is a cell surface molecule which is expressed on antigen presenting cells such as monocyte, macrophage, dendritic cells and neutrophils. The costimulatory pair, CD40 and CD40L, enhances T cell activation and induce chronic inflammatory disease. Also, DNA hypomethylation on CD40 promotor induces inflammatory monocyte differentiation in chronic kidney disease. In order to figure out if CD40 is a prototypic HM cycle regulated master gene, RNA-seq analysis were performed for CD40+ and CD40- monocytes from mouse peripheral blood and 1,093 differentially expressed genes (DEGs) were selected from those two groups. All the DEGs modulate as much as 15 functional gene groups such as cytokines, enzymes and transcriptional factors. Furthermore, CD40+ monocytes activated trained immunity pathways especially in Acetyl-CoA generation and mevalonate pathway. In HM cycle, CD40 is a prototypic HM cycle regulated master gene to induce the most of the Hcy metabolic enzymes as well as MT, which can further modulate the methylation-regulated pathological signaling.<br>Temple University--Theses
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Shaw, Nigel Anthony. "Cloning studies of the methionine high-affinity transport system of Salmomella typhimurium." Thesis, University of Hull, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253147.
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Kass, Carl. "Micro feeding machines in the dairy industry." Thesis, Kansas State University, 2018. http://hdl.handle.net/2097/38854.
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Master of Agribusiness<br>Department of Agricultural Economics<br>Allen M. Featherstone<br>Micronutrient machines have been used successfully in the beef industry, however, their use was mostly for the addition of antibiotics into the rations. Their use in the dairy industry has been very limited. Feed cost is over 50% of the total cost on a typical dairy farm, thereby creating an area where minor changes in cost per cow can impact the bottom line. Because of the high feed cost on dairy farms, income over feed cost (IOFC) is one of the bench marks as to the overall farm financial health. The feed rations also impact animal health incidences and reproduction efficiencies.
Micro machines can add small amounts of a desired nutrient or product, generally less than 56 grams (± 2 oz) into the cattle's daily total mixed rations (TMR). These micronutrients are generally expensive, and their inclusion into the rations of only cows that need that particular micronutrient is one benefit of a micro machine. Micro machines also take out the human error of mixing small accurate amounts and can easily track inventories. Benefits also include the control of on-farm shrink through dust control, and environmental stewardship of resources. Lastly, by creating options to accurately add micronutrients, milk production may be increased and health incidences reduced. The dairy industry is a virtually an untapped field for this technology and this research will explore if there is a benefit from their use. As feeding systems have evolved and milk production has continued to climb, innovative technologies will continue to be implemented. Increased financial pressures will also continue to cause producers to become more efficient with their resources.
As production increases in any field, fine tuning of inputs becomes more exact. The rumen inner workings and how feedstuff blends affect rumen micros and the pH levels is an area in which there is much research completed, however, much more is still needed. The addition of micro machines to fine tune rations for dairy farms TMR rations can be a profitable way to manage income over feed cost, not only by saving money spent on micronutrients but by increasing production and reducing herd health incidences.
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Mistry, Dineshkumar. "The vertebrate neuronal gamma-aminobutyric acid (GABAa) receptor and its modulation : a patch clamp study." Thesis, University of St Andrews, 1988. http://hdl.handle.net/10023/14452.
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Pressure application of gamma-aminobutyric acid (GABA) to mouse spinal and rat DBG neurones maintained in culture evoked transient membrane currents. Using the whole-cell patch clamp technique, these currents were shown to primarily involve the flow of Cl-. The GABA-evoked whole-cell currents in both types of neurones were reversibly suppressed by the GABAA antagonist bicuculline. The barbiturate phenobarbitone reversibly potentiated GABA-evoked whole-cell currents in mouse spinal neurones. Attempts to look at the unitary currents activated by GABA in outside-out patches, revealed spontaneous unitary currents. The I-V relationships of the spontaneous currents were linear and had a reversal potential of OmV in symmetrically distributed Cl solutions. Changing the monovalent cation concentrations on one or both sides of the membrane patch had no effect on the amplitude or the reversal potential of the spontaneous currents. Replacing some of the Cl- in the patch pipette with the impermeant anion SO42- shifted the reversal potential to more negative values. These spontaneous currents in both types of neurones were blocked by bath perfusion of bicuculline. GABA-activated unitary currents in outside-out patches, the main conductance state in both types of neurones was 30pS. However, GABA could occasionally also activate other conductance levels. Spontaneous Cl- currents did not occur in cell-attached patches from mouse spinal and rat DRG neurones, suggesting that the spontaneous events in the outside-out patches did not represent the activity of voltage dependent Cl- channels. Alphaxalone, a steroid anaesthetic, potentiated GABA-evoked whole cell currents in both spinal and DRG neurones. At high (muM) concentrations, pressure application of alphaxalone evoked a membrane Cl- current; this current was reversibly suppressed by blcuculline and potentiated by phenobarbitone. Pregnanolone (5beta-pregnane-3x-ol-20-one) a progesterone metabolite at low (nM) concentrations reversibly enhanced GABA currents in spinal neurones. Pregnanolone at higher concentrations pressure applied to spinal neurones had a weak direct agonist action on the GABAA receptor. Pregnanolone prolonged the burst duration of GABA-activated unitary currents in outside-out patches from spinal neurones. Some of the actions of the steroids on the GABAA receptor were very similar to the barbiturates, bemegride, a respiratory stimulant was formerly used clinically to counteract barbiturate poisoning in man. Experiments were conducted to see whether bemegride could be used as a specific barbiturate antagonist. Bemegride reduced phenobarbitone enhanced GABA currents in mouse spinal neurones. However, bemegride alone also reduced GABA and pentobarbitone evoked currants to a similar extent. This is suggestive of a noncompetitive action on the GABAA receptor, therefore it was not used to elucidate the site of action of steroids.
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El, Shafey Hatem Mohamed. "Identification du cofacteur métallique de la superoxyde dismutase de Corynebacterium glutamicum et clonage des gènes sodA et msrA et étude des régulations de l'expression sous stress oxydatif et radiatif." Paris 11, 2004. http://www.theses.fr/2004PA112018.
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La SOD cytosolique a été purifiée. Des expériences de substitution de métaux ont montré que la substitution par le manganèse permettait de conserver 84,9 % d'activité spécifique, alors que le cuivre, le fer, le nickel, et le zinc ne permettaient pas de restituer l'activité. L'enzyme est donc une MnSOD stricte (non-cambialistique). Le gène codant, sodA, a été cloné et séquencé. L'analyse du locus chromosomique a permis d'identifier dans l'environnement de sodA, un second gène (msrA, codant un peptide méthionine sulfoxyde réductase), potentiellement impliqué dans la réponse au stress oxydatif. L'analyse de la région promotrice sodA-msrA n'a pas permis de mettre en évidence les sites de fixation des régulateurs éventuels sauf des sites éventuels de fixation de OxyR et IHF. La régulation des deux gènes sodA et msrA a été étudiée par le suivi des variations de l'expression du gène lacZ de E. Coli, gène rapporteur placé sous le contrôle des séquences en amont de sodA et de msrA. Des fusions traductionnelles ont été construites, et intégrées dans le génome de C. Glutamicum. Diverses conditions environnementales de stress oxydatif, de stress radiatif, de stress thermique, ainsi que l'ajout de métaux in vivo ont été étudiées, mais aucun des stress utilisés n'a permis de révéler une régulation transcriptionnelle de sodA, ni de msrA, sauf pour msrA en phase stationnaire tardive en réponse au choc thermique, ou après irradiation UV. Une étude in silico pour chercher les régulateurs éventuels dans le génome de C. Glutamicum a montré l'absence des homologues de soxRS et arcA, la présence de oxyR, et de candidats putatifs homologues de ahpC, ohrR, crp-fnr, IHF, furA, IdeR,DtxR et mntR<br>The cytosolic SOD was purified. Experiences of metal substitution indicated that the substitution by manganese permitted the conservation of 84,9 % of specific activity, while the use of copper, iron, nickel, zinc did not permit to restore the activity. Thus the enzyme is a strict MnSOD (not-cambialistic). The sodA gene was cloned and sequenced. Analysis of the chromosomal locus allowed the identification of a second gene possibly implicated in oxidative stress response (peptide methionine sulfoxide reductase encoding gene msrA) in the close environment of the sodA gene. The analysis of the promoter region sodA-msrA did not make it possible to highlight the putative sites of fixing of the eventual regulators except possible sites of fixing of OxyR and IHF. Expression of the E. Coli lacZ gene, as a reporter gene placed under the control of the upstream sequences of sodA and msrA, was followed as a reflect of sodA and msrA regulation. Integrative transductionnal fusions were transferred into the C. Glutamicum genome. Various stresses: oxidative stress, radiative stress, heat shock, in vitro addition of metals was tried, but no regulation was detected for sodA and msrA expression, but in the case of msrA during late stationary phase in response to heat shock, and in response to UV irradiation. An in silico study to seek eventual regulators in the genome of C. Glutamicum showed the absence of the homologues of soxRS and arcA, the presence of oxyR, and the presence of putative candidates for ahpC, ohrR, crp-fnr family, IHF, furA, IdeR, DtxR and mntR
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Kadlčík, Vojtěch. "Oxidation of beta-amyloid and model peptides." Paris 11, 2006. http://www.theses.fr/2006PA112008.
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Le but de mon travail de thèse était de caractériser les produits de l'oxydation du peptide beta-amyloïde (Abeta) impliqué dans le développement de la maladie d'Alzheimer. Pour étudier l'effet de la structure de peptide sur les processus redox, les propriétés du peptide Abeta (1-40) ont été comparées au peptide de séquence inverse, Abeta (40-1). Les radicaux libres choisis ont été produits en radiolyse gamma. Les produits finaux ont été caractérisés par des techniques d'analyse diverses (HPLC, GC, MALDI-TOF MS, spectrométrie de fluorescence, spectrométrie raman). Pour établir l'effet de l'environnement sur le processus d'oxydation, peptides ont été oxydés dans trois systèmes différents: solution aqueuse homogène, milieu micellaire (SDS) et système des vésicules phospholipidiques (POPC). En solution aqueuse homogène, les produits d'oxydation sont différents pour les deux peptides. Les résidus facilement oxydables sont Met35 pour Abeta(1-40) et Tyr10 pour Abeta(40-1). La présence des micelles ainsi que des vésicules phospholipidiques change profondément le cours de l'oxydation. Une étude structurale en dichroïsme circulaire nous permet d'avancer des hypothèses pour interpréter ces résultats. Nous avons montré que des produits de dégradation des peptides Abeta peuvent induire d'une manière catalytique l'altération des phospholipides. Cette propriété est attribuée à l'action des atomes d'hydrogène sur le peptide. Nos résultats sont intéressants dans le contexte du développement de la maladie d'Alzheimer, car ils peuvent aider à éclairer le rôle de l'interaction de peptide Abeta(1-40) avec des membranes phospholipidique dans les propriétés redox du peptide<br>The goal of my thesis work was to characterize oxidation products of beta-amyloid peptide (Abeta), which is implied in the development of Alzheimer's disease. To study the effect of peptide structure on the redox processes, oxidation properties of Abeta(1-40) were compared to the peptide with reverse sequence, Abeta(40-1). Azide and hydroxyl radicals used for oxidation were produced by gamma radiolysis. Final products were characterized by a variety of analytical techniques (HPLC, GC, MALDI-TOF MS, fluorescence and raman spectrometry). To establish the role of peptide environment on its redox properties, oxidation was carried out in three different systems: homogeneous aqueous solution, micellar system (SDS) and in the presence of phospholipids vesicles (POPC). In homogeneous aqueous solution, oxidation products are different for both peptides. The main oxidation targets are Met35 for Abeta(1-40) and Tyr10 for Abeta(40-1). The presence of micelles and phospholipid vesicles has an important impact on the oxidation pathways. These changes could be related to changes in peptide conformations studied by circular dichroism. We have also shown that Abeta degradation products may catalytically induce alternation of phospholipids. This process is initiated by reaction of hydrogen radicals with the peptide. Our results are interesting in the context of the development of Alzheimer's disease as they may bring an insight into the role of Abeta(1-40) interaction with phospholipids membrane for the redox properties of the peptide
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Coope, David John. "Use of [11C]-methionine PET and diffusion-/perfusion-weighted MR imaging in gliomas." Thesis, University of Manchester, 2010. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:207525.
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Introduction: Low-grade gliomas are a sub-group of primary brain tumours that typically affect young adults and which present specific challenges to conventional diagnostic imaging. They demonstrate a pattern of growth whereby tumour cells infiltrate healthy brain tissue without distortion of the surrounding brain or blood-brain barrier integrity. These features limit the capacity of conventional neuro-imaging strategies to effectively delineate the tumour extent or characterise the degree of 'malignancy'. One solution is to apply multiple imaging modalities to image different aspects of the tumour behaviour, analogous to histological classification based upon changes in mitotic activity, cellular atypia, microvascular proliferation and necrosis. Published information regarding how imaging techniques that address these parameters correlate within the tumour volume is limited. This reflects the technical challenges in acquiring and processing data at an adequate spatial resolution to characterise small but heterogenous tumours. In this thesis, following a series of experiments seeking to optimise the sensitivity and reproducibility of PET analysis in gliomas, a prospective multi-modal neuro-imaging study is presented addressing this need. Methods: Retrospective [11C]-methionine PET (MET PET) data made available through a collaboration with the Max-Planck Institute for Neurological Research in Cologne was carried out first to address the optimal method of analysis of PET data in gliomas. A normal methionine uptake map was created and its use in the analysis of patient scans validated against a conventional approach. Automated methods for delineating the extent of abnormal methionine uptake and identifying the region of peak uptake were developed and evaluated to optimise the reproducibility of the approach. High-resolution MET PET and a comprehensive MRI brain tumour protocol were then acquired prospectively in 20 subjects in Manchester. Detailed analysis of the peak uptake and extent of abnormal tissue defined using PET and MRI modalities including structural, diffusion- and perfusion-weighted techniques was performed. Results: Evaluation of methionine uptake with respect to population normal data, the 'RatioMap' technique, yielded peak uptake measurements that correlated closely with a conventional approach (r = 0.97) but with improved reproducibility. The constrained 3D region-growing algorithm designed to delineate the abnormal region was shown to be reproducible and to generate volumes that correlated with tumour grade. High-resolution multi-modal data in suspected low-grade gliomas demonstrated consistent correlation between peak methionine uptake ratio and peak regional cerebral blood volume (r = 0.85) but with disparity between the location of the maximal uptake regions (mean distance = 11.2mm). Significant correlation was seen between multi-modal MRI and PET ‘tumour’ volumes (r = 0.91) but with substantially larger MRI defined abnormal volumes (ratio = 2.0) including small regions identified as abnormal by multiple MRI parameters but normal on PET imaging. Conclusion: A novel method to enhance the reproducibility of analysis of MET PET images in gliomas has been presented and validated but there remains no single imaging modality capable of fully characterising glioma extent and 'malignancy' non-invasively. Considerable correlation between PET and MRI tumour biomarkers has been demonstrated but there are significant differences between the regions identified as the 'most malignant' for biopsy targeting and the extent of potentially tumour bearing tissue. Combined use of diffusion- and perfusion-weighted MRI parameters can provide results very closely correlated to the PET findings but cannot yet completely replace the use of nuclear medicine techniques. The use of multi-modal approaches to tumour characterisation as demonstrated in this study provides the most effective currently available approach to fully characterise a suspected glioma.
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Shalchi-Toosi, Marjan. "Implications of methionine and S-adenosylmethionine for the brain function." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26132.
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We have studied the effect of S-adenosylmethionine (SAM) on tail flick latency in the rat. We also studied the effect of methionine the immediate precursor of SAM. Administration of methionine to the rat increases brain SAM, but little is known about its behavioral effects. Long-Evans rats were given SAM and methionine orally at different doses and tail-flick latency was measured at various times. Both methionine and SAM increased tail-flick latency, but methionine did so at a lower dose. A biochemical study showed that methionine was more effective than SAM in raising brain SAM probably because it is transported better into brain. The biochemical measurements were not consistent with the idea that the effects of SAM and methionine were mediated by an increase in brain 5-HT.<br>Folate deficiency can lower brain SAM levels and cause depression. Thus, methionine, which raises brain SAM, may overcome the effects of folate deficiency. Seven day food records were done by 26 psychiatric outpatients who were stable on lithium treatment. Eight patients had mean daily folate intakes below those recommended. Some of those with low folate intake had high methionine intake consistent with the idea that methionine could substitute metabolically for folate deficiency. Daily methionine intakes ranged from 13 to 304% of the recommended intake. As methionine had behavioral effects in the rat at doses much less than the daily dietary intake this raises the question of whether varying daily intakes of methionine in humans have behavioral implications. (Abstract shortened by UMI.)