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1
Lara, Maria Cristina Figueiredo Lima e. « Estudos das interações do íon Cu2+ com os dipeptídeos glicil-triptofano e triptofil-glicina ». Universidade de São Paulo, 1993. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-25022014-114118/.
Texte intégralRésumé :
Neste trabalho, são estudados dois dipeptídeos complexados com cobre, Triptofil-Glicina (trp-Gly) e Glicil-Triptofano (Gly-Trp). Focalizamos a interação com o metal de transição, mudanças conformacionais, papel do resíduo pesado de triptofano na simetria dos complexos formados, e explicamos as propriedades espectroscópicas atípicas que observamos no Gly-Trp: Cu+2 em pH´s altos semelhantes aquelas apresentadas em uma espécie de proteínas naturalmente complexadas as proteínas azuis. Para atingirmos tais objetivos, lançamos mão das técnicas de RPE, Dicroísmo Circular (CD) e Absorção ótica, pelas suas complementaridades. Com os dados experimentais, propusemos dois modelos para os complexos com suas funções de onda. Para Trp-Gly: Cu+2, nos pH´s 9,1 e 13,2 e para o Gly-Trp: Cu+2 no pH= 9,1 propomos um modelo que chamamos de covalente. Que consiste basicamente em considerar que os orbitais do íon Cu+2 e seus ligantes, se encontram em simetria quadrado planar (D4h) e que cada ligante no caso nosso, dois oxigênios e dois nitrogênios, tem disponíveis seus orbitais 2s, 2px, 2py, 2pz para a formação dos orbitais moleculares com os orbitais 3d do cobre. As funções assim construídas, dependem de coeficientes que nos dão informações sobre o grau de covalência. O método é semi-empírico. As expressões teóricas dos parâmetros RPE dependem destes parâmetros de covalência e das energias de transição obtidas por absorção ótica no visível. Pudemos então com os valores experimentais das componentes dos tensores g e A obtermos os valores numéricos dos parâmetros de covalência. Para o complexo Gly-Trp: Cu+2, no pH=13,2, propusemos o modele de mistura de orbitais, um modele não covalente que consiste em considerarmos as funções de onda dos estados excitados 4s e 4p do cobre misturadas com as dos orbitais 3d do mesmo íon, para explicar as propriedades espectroscópicas pouco comuns, que se deslocam na direção daquelas obtidas nas proteínas azuis. Conhecendo os valores experimentais das componentes dos tensores g e A, da força de oscilador obtida dos espectros óticos e da força rotacional obtida dos espectros CD, e das auto-funções compatíveis com o modelo, determinamos numericamente os coeficientes de hibridização (mistura). Os parâmetros experimentais, foram determinados através de simulações espectrais, utilizando programas desenvolvidos para este fim. Através deste trabalho, pudemos enfim, verificar a influência do resíduo pesado de triptofano na estereoquímica dos complexos formados, mudanças de simetria, o caráter das ligações, e ate que ponto as propriedades do dipeptídeo Gly- Trp: Cu2+ em pH alto, são semelhantes às proteínas azuisIn this work we studied two dipeptide-copper complexes, being Triptofil-Glycine (Trp-Gly) and Glycil-Triptophan (Gly-Trp). We focused our interest on the interaction with the transition metal, conformational changes and the role that the heavy residue of the Triptophan plays in the symmetry of the complex. Moreover we explain the unusual spectroscopic properties that we observed with Gly-Trp: Cu+2 in high pH solutions similar to that of the so called blue proteins. For these purposes we used such complementary techniques as EPR, Circular Diochrism and Optical Absorption Spectroscopy. Based on our experimental results we proposed two models for the complexes and their wave functions. For the TRP-Gly: Cu+2 in pH of 9.1 and 13.2 and for Gly-Trp: Cu+2 with pH=9.1, we use a model which we call covalent. It consists basically of the consideration that the electronic orbital of the ion Cu+2 and its ligands are in square planar symmetry and that each of the four ligand atoms, in our case two oxygen and two nitrogen atoms, has available 2s, 2px, 2py, 2pz for the formation of molecular orbital with the copper 3d orbital. The wave functions thus constructed depend on coefficients (parameters) that give information on the degree of the covalent character of the bond (complex). The method is semi-empirical. The theoretical expressions for the EPR parameters depend on these coefficients and the transition energies obtained by absorption spectroscopy (in the visible). With the experimental values of the g and A tensors we can therefore obtain numerical values for the covalent coefficients. For the complex Gly-Trp: Cu+2 with pH=13.2 we proposed a model of mixing orbital, a non covalent model that consists of the assumption that the wave functions of the excited states 4s and 4p of the copper mix with the 3d orbital of the same ion. With this model it was possible to explain the uncommon spectroscopic properties that are similar to these of the blue proteins. Knowing the experimental values of the components of the tensors g and A, the oscillator strength obtained by the optical spectra, the rotational strength obtained by the CD spectra and the eigen-functions compatible with the model, we numerically determined the coefficients of hybridization. The experimental parameters were determined by spectral simulations using programs that we developed especially (specifically) for this purpose. Trough this work it was possible to verify the influence of Triptophan on the stereochemistry (stereo chemical behavior) of the formed complexes, on symmetry changes, covalent character and up to which point the properties of the dipeptide Gly-Trp: Cu+2 in high pH are similar to that of the blue protein
2
Fu, Rong. « Biochemical and Spectroscopic Characterization of Tryptophan Oxygenation : Tryptophan 2, 3-Dioxygenase and Maug ». Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/chemistry_diss/44.
Texte intégralRésumé :
TDO utilizes b-type heme as a cofactor to activate dioxygen and insert two oxygen atoms into free L-tryptophan. We revealed two unidentified enzymatic activities of ferric TDO from Ralstonia metallidurans, which are peroxide driven oxygenation and catalase-like activity. The stoichiometric titration suggests that two moles of H2O2 were required for the production of one mole of N-formylkynurenine. We have also observed monooxygenated-L-tryptophan. Three enzyme-based intermediates were sequentially detected in the peroxide oxidation of ferric TDO in the absence of L-Trp including compound I-type and compound ES-type Fe-oxo species. The Fe(IV) intermediates had an unusually large quadrupole splitting parameter of 1.76(2) mm/s at pH 7.4. Density functional theory calculations suggest that it results from the hydrogen bonding to the oxo group. We have also demonstrated that the oxidized TDO was activated via a homolytic cleavage of the O-O bond of ferric hydroperoxide intermediate via a substrate dependent process to generate a ferrous TDO. We proposed a peroxide activation mechanism of the oxidized TDO. The TDO has a relatively high redox potential, the protonated state of the proximal histidine upon substrate binding as well as a common feature of the formation of ferric hydroxide species upon substrate or substrate analogues binding. Putting these together, we have proposed a substrate-based activation mechanism of the oxidized TDO. Our work also probed the role of histidine 72 as an acid-base catalyst in the active site. In H72S and H72N mutants, one water molecule plays a similar role as that of His72 in wild type TDO. MauG is a c-type di-heme enzyme which catalyze the biosynthesis of the protein-derived cofactor tryptophan tryptophylquinone. Its natural substrate is a monohydroxylated tryptophan residue present in a 119-kDa precursor protein of methylamine dehydrogenase (MADH). We have trapped a novel bis-Fe(IV) intermediate from MauG, which is remarkably stable. A tryptophanyl radical intermediate of MADH has been trapped after the reaction of the substrate with the bis-Fe(IV) intermediate. Analysis by high-resolution size-exclusion chromatography shows that MauG can tightly bind to the biosynthetic precursor and form a stable complex, but the mature protein substrate does not.
3
Walsh, Harold Archibold. « Regulation of tryptophan-2,3-dioxygenase and pineal indoleamines by selected tryptophan derivatives and antidepressants ». Thesis, Rhodes University, 1997. http://hdl.handle.net/10962/d1004077.
Texte intégralRésumé :
The regulation of tryptophan-2,3-dioxygenase (TDO) (EC 1.13.1.12) and, to a lesser extent, pineal indoleamines, both in vitro and in vivo, is examined in this study. Rat liver TDO is a cytosolic enzyme which plays a crucial role in the regulation of circulating tryptophan (TRP) levels. Stimulation of this enzyme by heme enhances the catabolism of TRP, making less TRP available for uptake into the brain and other tissues, and for protein synthesis. At pH 7, the enzyme has an approximate Km of 100μM, is subject to substrate inhibition immediately beyond Sopt([S] at Vmax), and response of the enzyme is cooperative in both uninhibited and inhibited regions. Hill analysis of the uninhibited region reveals a biphasic plot and two classes of binding sites. Negative cooperativity is brought about through deprotonation of the enzyme. Substrate iphibition also occurs at both acidic and basic pH values with concomitant shifts in Sopt. The results obtained indicate that substrate inhibition could be an additional mechanism whereby the flux through the TRP-kynurenine pathway is regulated. TDO is subject to a diurnal rhythm, with peak activity during the pre-dark period and the loweSt activity towards the end of the dark period. It is possible that the enzyme controls the synthesis of the neurotransmitter serotonin (5-HT), and that the circadian rhythm in TDO activity is due to the endogenous rhythm of melatonin (aMT) production by the pineal gland. In the present study, aMT displaces TRP from bovine serum albumin (BSA) in vitro, and it is therefore possible for the indoleamine to regulate the availability of TRP for uptake into the brain for conversion to its derivatives. Chronic intraperitoneal administration of aMT affects physiological hepatic parameters in rats, such as TDO activity and stromal fatty acid composition, whilst no observable effect is demonstrable with respect to protein synthesis, nucleic acid metabolism, membrane fatty acid composition and pineal indole biosynthesis. On the other hand, chronic treatment of rats with antidepressants, the tricyclic desmethylimipramine (DMI) and the selective serotonin reuptake inhibitor (SSRI), fluoxetine, reveals significant negative alterations in TDO concentrations and pineal indole amine synthesis. Combining aMT with any of these two drugs normalises the activity of the hepatic enzyme. DMI is found to be an effective inhibitor of TDO in the micromolar range in vitro, and also affects total enzyme concentrations in vivo. Fluoxetine has no effect on TDO in vitro, but in vivo also reduces total enzyme levels in the liver. However, the SSRI does not affect conjugation between apo- and holoenzyme. Instead, it decreases extant holoenzyme levels. Indoleamine synthesis by the pineal gland, in organ culture, is altered by both antidepressants, although in different ways. DMI increases N-acetylserotonin levels and reduces the output of methoxyindole acetic acid and meth6xytryptophol. Fluoxetine treatment markedly reduces aMT concentrations and also brings about high levels of the 5-HT catabolites, 5-hydroxytryptophol and 5-hydroxyindole acetic acid. Insulin also lowers aMT synthesis significantly in pineal organ cultures, via a mechamsm that involves inhibition of the enzyme, N-acetyl transferase, that regulates aMT synthesis. The effects of insulin on pineal indole metabolism are due to the observation that a carbohydrate rich diet which induces insulin release elevates plasma TRP and brain 5-HT, but has no effect on pineal TRP and indole amine synthesis. It could thus be possible for insulin to have an effect on the pineal, since the latter is outside the blood brain barrier. The finilings of this study support the biogenic amine deficiency hypothesis, implicating some of the major biogenic amines such as noradrenaline (NA), 5-HT and aMT in depression. There is believed to be a deficiency of NA and 5-HT at their respective synapses in the depressed state. The drug DMI could act, firstly, by inhibiting TDO and thus increasing plasma TRP levels, and could, secondly, stimulate NA release and inhibit NA reuptake at the pineal membrane. The combined effect would be to enhance aMT synthesis, with eventual remission. Fluoxetine, on the other hand, appears to utilize a slightly different mode of action to DMI, which seems to focus on the preservation of 5-HT. The fact that aMT counteracts the effects of both antidepressants, and restores the activity of TDO to that of the controls, is also consistent with the observation that the therapeutic action of drugs such as these coincides willi the restoration of normal plasma levels of the neurohormone in depressives. In view of the biogenic amine deficiency hypothesis of depression and the contentious claim that TDO is the major peripheral determinant of brain TRP, brain 5-HT and ultimately aMT, the regulation of TDO is investigated and discussed. The study concludes that TDO activity is regulated by a number of endogenous compounds which are mainly derivatives of TRP, such as aMT and oxidized nicotinamide adenine dinucleotide and exogenous substances, of which DMI and fluoxetine are but two. In addition, modulation of IDO activity in depression appears to be an important aspect of antidepressant action. aMT, the product of the pineal gland, also has the potential to increase plasma TRP and hence forebrain TRP levels, and ultimately 5-HT concentrations, firstly by displacing TRP from serum albumin and secondly by inhibiting TDO.
4
Brnardic, Edward Joseph. « Synthesis of aza-tryptophan derivatives ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0013/MQ52518.pdf.
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Schaechter, Judith Diane. « Tryptophan availability modulates serotonin release ». Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/13995.
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Tsimpos, Kleomenis. « Τοwards a Synthetic Tryptophan Aminotransferase ». Thesis, Linnéuniversitetet, Institutionen för kemi och biomedicin (KOB), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-97548.
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The synthesis and evaluation of a molecularly imprinted polymer has been undertaken using an oxazine-based tryptophanamide transition state analogue (TSA) as template. An efficient route to the synthesis of oxazine-based TSAs for the reaction of pyridoxamine and indole-3-pyruvic acid has been established, with yields of up to 80%. NMR titration studies were performed to examine the interactions between the functional monomer, methacrylic acid and the template. Complexation of the template by functional monomer in the presence of crosslinker showed an apparent KD of 0.63-0.79 ± 0.04 M (293 K, acetonitrile-d3) based upon the chemical shift of the template amide protons. TSA-imprinted and non-imprinted reference polymers were synthesized by free radical polymerization in acetonitrile. Polymer monoliths were ground and fractionated into a 25-63 μm size range. Polymer-ligand recognition studies were conducted using the polymers as HPLC stationary phases. An imprinting factor (IF) of 2.93 was observed for the TSA, indicating the selectivity of the imprinted sites for the template. Studies using the D- and L-enantiomers of the phenylalaninamide analogue of the template showed enantioselectivity in the case of the imprinted polymer, α = 1.10, though not in the case of the non-imprinted reference polymer (1.00). Using UV-spectroscopy based polymer-ligand binding studies, a maximum theoretical capacity (Bmax) of 0.059 ± 0.004 mmol·g-1 was observed for the imprinted polymer. Conclusively, an imprinted polymer with binding sites selective for the TSA was successfully prepared and shall subsequently be studied with respect to its capacity to catalyse the transamination reaction between pyridoxamine and indole-3-pyruvic acid to yield pyridoxal and tryptophan.
7
Mirzaei, Hamid. « Synthesis of tryptophan amides and lavendamycin analogs ». Virtual Press, 2001. http://liblink.bsu.edu/uhtbin/catkey/1221298.
Texte intégralRésumé :
The synthesis of 7-N-acetyl-3'-demethyllavendamycin propyl ester (61 ), 7-N-butr-3'-demethyllavendamycin amide of N,N-dimethylethylenediamine (62), 7-N-acetyllavendamycin butyl amide (64), 7-N- acetyllavendamycin amide of ethanolamine (63) are described. Incorporation of the Pictet-Spengler condensation of 7acetamido-2-formylquinoline-5, 8-dione (32) or 7-butyramido-2-formylquinoline-5, 8dione (7) with tryptophan propyl ester (65), L-tryptophan amide of N, N dimethylethylenediamine (66), f3-methyltryptophan butyl amide (68), or methyltryptophan amide of ethanolamine (67) in xylene afforded four lavendamycin analogs.Aldehydes 32, 74 and 86 were prepared according to the following general procedure. Nitration of 8-hydroxy-2-methylquinoline (69) yielded 8-hydroxy-2-methyl - 5,7-dinitroquinoline (29). Compound 29 was then hydrogenated and acylated with acetic anhydride or butyric anhydride or 2-furoyl chloride followed by hydrolysis to yield 5,7diacetamido-8-hydroxy-2-methylquinoline (75) or 5,7- dibutyramido-8- hydroxy-2methylquinoline (73) or 5,7-difuroylamino-8-hydroxy-2- methylquinoline (84). Compounds 75 and 73 and 84 were oxidized by potassium dichromate to give the corresponding 5,8-diones 31 or 72 or 85. Treatment of 31 or 72 or 85 with selenium dioxide in refluxing 1,4-dioxane afforded compounds 32 and 74 and 86, respectively.Tryptophan propyl ester (65) was synthesized via a Fischer esterification of Ltryptophan with propyl alcohol saturated with hydrogen chloride. Compounds 66, 67, 68, 76, 77, 78, 79, and 80 were synthesized via the conversion of esters to amides with dimethylaluminum amides. Tryptophan methyl ester (23) and (3-methyltryptophan methylester (11) were treated with premixed trimethylaluminum and primary amines and refluxed to afford the desired tryptophan and (3-methyltryptophan amides.The structures of the novel compounds 61, 62, 63, 64, 66, 67, 68, 76, 77, 78, 79, 80, were confirmed through 1H NMR, IR, EIMS, and HRMS. Elemental analyses of Compounds 66, 68, 76, 77, 78 and 80 were also included. 1H NMR and IR for known compounds 29, 30, 31, 32, 71, 73, 74, 75, 84, 85, 86 were provided also.Department of Chemistry
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Bergqvist, Peter B. F. « Tryptophan-related neurotransmission in the brain disturbances associated with experimental hepatic encephalopathy / ». Lund : Dept. of Clinical Pharmacology, Institute of Labortaory Medicine, Lund University Hospital, 1997. http://catalog.hathitrust.org/api/volumes/oclc/39761954.html.
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Müller, Burkhardt. « Synthese, Analytik und Bildungsbedingungen von Kontaminanten in biotechnologisch hergestelltem Tryptophan ». [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=957463723.
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Solle, Dörte. « Analyse und Optimierung eines industriellen Biotransformationsprozesses zur Herstellung von Tryptophan ». [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969294492.
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Bae, Jae Hyun. « Studies on tryptophan analogues in proteins ». [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966131681.
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Remes, Lenicov Federico. « Transcriptional regulation of tryptophan hydroxylase-2 ». Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27413.
Texte intégralRésumé :
Dysregulation of serotonergic neurotransmission is a contributing cause of numerous pathologies. In the brain, the enzyme catalyzing the rate-limiting step in serotonin biosynthesis and thus controlling serotonin levels is tryptophan hydroxylase-2 (TPH2). The objective of this project is to study the regulation of TPH2 transcription by characterizing its promoter region.
Study of the 5' flanking region of the human TPH2 gene by means of reporter gene assays resulted in the finding of a core promoter and a repressing element between positions -179 and -88 relative to the transcription start site. In addition, the TPH2 promoter could be activated by Ca++ mobilization in a cell-line model of serotonergic neurons, but not in other cell lines. In agreement, Ca++ mobilization in this model also induced endogenous transcription of TPH2.
This work is the first one to identify the promoter region of the TPH2 gene and to report its activity-dependent regulation of transcription.
13
Parmar, Anil. « Model chemistry of tryptophan tryptophylquinone cofactor ». Thesis, University of Leicester, 2010. http://hdl.handle.net/2381/7958.
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This report covers the model chemistry conducted on the tryptophan tryptophylquinone (TTQ) cofactor 1. The synthesis of the TTQ model compound 13 was established and optimised, starting from o-anisidine (40). Different strategies were attempted to increase the yield of indole-ester compound 42, which was the lowest yielding reaction (38%) in the synthesis of the TTQ model compound 13. The electronic effects on the catalytic oxidation of p-substituted benzylamines by the TTQ model compound 13 have been studied. The TTQ model compound 13 was found to act as an efficient catalyst for the formation of imines 35, 76 and 82. The electronic effect on the aerobic oxidation of p-substituted benzylamines 72, 74 and 80 by TTQ model compound 13 was found to be minimal. The KIEs for benzylamine oxidation by the TTQ model compound 13 have also been investigated. The apparently very large KIE of 48 indicated that the reaction when deuterated benzylamine (87) was used is proceeding slower than expected, compared to the KIE of 9.2 observed by Itoh and co-workers.36 A possible route to a water-soluble derivative of the TTQ model compound 13 has been investigated. The aqueous solubility of the indole 89 was found to be sufficient for the proposed kinetic studies to be carried out using the indole-quinone 91, which is derived from indole 89. Possible routes to the syntheses of other TTQ analogues have also been investigated. A major synthetic achievement was the faster and more efficient synthesis of the TTQ analogue 36 than that reported by Itoh and coworkers. 34, 40 The synthesis of the TTQ analogue 101 was two-steps from completion and the synthesis of the TTQ analogue 102 was three-steps from completion.
14
Jiang, George Chih-Thai. « Structure and function of tryptophan hydroxylase / ». Connect to electronic thesis, 2003. http://dspace.zsr.wfu.edu/jspui/handle/10339/192.
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Thesis (M. S.)--Wake Forest University Graduate School of Arts and Sciences, Molecular Genetics Program, May 2003.Kent E. Vrana, advisor. Includes curriculum vita. Includes bibliographical references.
15
Jusof, Felicita Fedelis. « Tryptophan-catabolising enzymes in animal models ». Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/13697.
Texte intégralRésumé :
The first and rate-limiting step of the kynurenine pathway is the metabolism of tryptophan (Trp) to N-formylkynurenine, which is then rapidly converted to kynurenine. This initial step can be catalysed by three enzymes, tryptophan 2,3-dioxygenase (TDO), indoleamine 2, 3-dioxygenase-1 (IDO1) and the most recently discovered, IDO2. In adult mammals, TDO is expressed constitutively in the liver and is involved in the global regulation of tryptophan. IDO1 expression is mainly induced in various tissues during inflammatory conditions. IDO2, detected in the adult liver, may play a role in inflammation and autoimmune diseases. This report demonstrates the cellular localisation of IDO2 in adult mouse liver with Ido2-/- mice as the negative control, as well as the mRNA expression of Trp-catabolising enzymes in embryonic developmental series of zebrafish (tdo2a, tdo2b and ido) and mouse (Tdo2, Ido1 and Ido2). Both tdo2a and tdo2b were detected in zebrafish embryonic liver, whereas all three genes coding for Trp-catabolic enzymes were found in the intestine. In murine developmental tissues, Tdo2, Ido1 and Ido2 were all detectable in the yolk sac and placenta, with the expression of Tdo2 being the highest. Finally, this report also is the first to postulate a possible role for IDO2 in averting inflammation and metabolic dysregulation in the liver.
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Marshall, Eve. « Biomimetic approaches to tryptophan-derived alkaloids ». Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41344/.
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Chapter One describes several natural products derived from the amino acid tryptophan including the structures of the new natural products hyrtioseragamine A and B and tintamine. Chapter Two describes the work towards hyrtioseragamine A and B. It was intended that the unknown furo[2,3-b]pyrazine-2(1H)-one core would be synthesised from a 1,4-dicarbonyl and this has been synthesised from the amino acid ornithine and the tryptophan derivative kynurenine. Cyclisation of this material to give the 2,3-amino-furan was unsuccessful and thus a number of model systems were synthesised to examine the barrier to furan formation. These models suggest formation of a furan with nitrogen at its 2- and 3-positions was not possible by this route, and further attempts to install a nitrogen to a 2-amino-furan also proved unsuccessful. Chapter Three describes work on the synthesis of the marine natural product tintamine. This novel compound contains a unique tropo-1,2-dihydro-3,6-phenanthroline core and our synthesis was based on biomimetic principles. A Friedlӓnder reaction allowed successful formation of the quinoline and the attached seven-membered ring was further functionalised to a tropolone. Formation of the dihydro-phenanthroline was successful; it was also possible to separately functionalise the tropolone-quinoline with the sulfur side chain present in tintamine. Unfortunately several of the key intermediates of this route proved unstable, and at this point a final deprotection to form the natural product has not been successful. Chapter Four contains the synthetic details for the preparation of the novel compounds described in Chapters Two and Three.
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Cowan, Peter J. « Controlled production of tryptophan by genetically-manipulated strains of Escherichia coli ». Connect to thesis, 1992. http://repository.unimelb.edu.au/10187/1020.
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The tryptophan productivity of the genetically-manipulated strain JP4153 was increased 2.5-fold by introducing pMU78, a medium copy-number plasmid carrying a feedback-resistant trp operon. JP4153(pMU78) produced 23.5 g/l of tryptophan at a rate of 0.7 g/l/h when grown at 37 degrees C in a defined glucose and ammonium salts medium in a bench-scale fermentor.During prolonged cultivation in the presence of antibiotic, the recombinant strain generated faster-growing, production-defective variants, which harboure mutated derivatives of pMU78. Insertion sequences were responsible for the two predominant types of mutation. The plasmid element ISI02 mediated deletions extending into the promoter-proximal region of the plasmid-borne trp operon. ISI0-Right, a chromosomal element, inserted into the promoter/trpE region of the plasmid. Three methods were employed to increase the structural stability of JP4153(pMU78) during the course of the production process. First, the growth of seed cultures was carried out at 30 degrees C, the permissive temperature for the trpS378 mutation carried by the host strain. Second, the seed culture medium was modified by the addition of yeast extract, which appeared to reduce the selective disadvantage conferred by the plasmid. Third, ISI02was deleted from pMU78 to create pMU88. (For complete abstract open document)
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Tanda, Sindiswa Eunice. « The effect of 6-Methoxy-2-Benzoxazolinone (6-MBOA) on indoleamine regulation and its possible role in depression ». Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1003971.
Texte intégralRésumé :
Tryptophan is an essential amino acid that is obtained from the diet. Approximately 98 % of ingested tryptophan is metabolized by the enzyme tryptophan 2,3-dioxygenase (TDO). The metabolism of tryptophan by TDO is an important determinant of tryptophan bioavailability to the brain for serotonin (5-HT) biosynthesis, an essential amine in affective disorders such as depression. Studies done on circadian rhythmicity of the enzyme activity have shown that, TDO activity is high during the scoto-phase (dark-phase), which is attributable to the de novo enzyme synthesis that occurs during this phase. 6-Methoxy-2-benzoxazolinontr-(6-MBOA), a structural analogue of melatonin (aMT) was shown to inhibit TDO activity in both the photo-phase (light-phase) and the scoto-phase with greater potency during the light-phase. Further studies were directed at demonstrating the effects of 6-MBOA on the brain tryptophan hydroxylase (TH) activity, which is a rate limiting enzyme in 5-HT biosynthesis and subsequently on 5-HT levels. The findings showed that, 6-MBOA induces TH activity with a concomitant rise in brain 5-HT levels. The blockade of 5-HT re-uptake into the presynaptic neuron leads to an increase in 5-HT available for the stimulatory action of 5-HT receptors. An attempt to establish whether the administration of 6-MBOA would block the binding of 5-HT to receptors on the synaptosomal membrane showed that 6-MBO A only inhibits the binding of 5 -HT at specific concentrations. In view of the positive effects imposed by 6-MBOA on brain 5-HT levels, urinary 5-hydroxyindole acetic acid (5-HIAA) excretion was measured before and after treatment with 6-MBOA. 5-HIAA excretion was found to be significantly increased after 6-MBOA treatment. Extensive research on the biosynthesis of pineal metabolites has been conducted in the past two decades. The pineal metabolites are synthesized from the precursor tryptophan. In order to obtain an overall picture of the effect of6-MBOA on pineal indole metabolism, an organ culture technique was employed. The results obtained showed that although 6-MBOA administration to rats caused a significant increase in aMT production, there was an insignificant increase in NAS production. This is an immediate precursor of aMT. Other pineal indoles were not affected at all by 6-MBOA administration. Furthermore, the production of pineal NAS and aMT showed an inter-individual variation with some animals producing very high, some very low and some produced average levels of these two metabolites in both photo and scoto-phase experiments. A study undertaken to investigate the circadian rhythm in endogenous aMT production using the competitive ELISA technique showed a clear pattern with high levels of aMT produced during the dark-phase and low levels ofaMT produced during the light-phase. Furthermore, the administration of6-MBOA to rats lead to a significant rise in endogenous aMT production.
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Ernyei, Aliz Judit [Verfasser]. « Untersuchungen zur Substratspezifität der Tryptophan-5- und der Tryptophan-6-Halogenase und Optimierung der Reaktionen / Aliz Judit Ernyei ». München : Verlag Dr. Hut, 2014. http://d-nb.info/104799500X/34.
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Maitland, Smith Kevin Charles. « Tryptophan metabolism during reproduction in the rat ». Thesis, King's College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243546.
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Booth, Elizabeth Suzanne. « Tryptophan oxidation by the heme-containing dioxygenases ». Thesis, University of Leicester, 2016. http://hdl.handle.net/2381/37091.
Texte intégralRésumé :
In biology, the kynurenine pathway is the major degradation pathway of tryptophan (L-Trp). The first and rate-limiting step is the oxidation of L-Trp to N-formylkynurenine (NFK). The mechanism of this oxygen-dependent reaction has not been established, but is catalysed by two heme-containing dioxygenase enzymes: indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO). Early proposals suggested a base-catalysed abstraction mechanism, but most of the recent studies argue against that. Instead, formation of a ferryl (Compound II intermediate) seems more likely. In this thesis, aspects of the reaction mechanism have been investigated. A Compound II intermediate was detected during the oxidation of L-Trp by hIDO using stopped flow photodiode array spectroscopy. A Compound II intermediate was also detected during the oxidation of a number of different tryptophan analogues. The results suggest a common mechanism of oxidation between L-Trp and other substrates of hIDO. The difference in reactivity between the tryptophan analogues 5-hydroxy-tryptophan and 5-methoxy-tryptophan with hIDO have been interpreted to indicate that initial oxygen atom insertion occurs by radical rather than electrophilic addition. An intermediate was detected during the oxidation of L-Trp by hTDO and XcTDO. The spectrum of this intermediate did not appear to be characteristic of a Compound II based on comparison with the spectrum of Compound II from hIDO. Weaker binding of L-Trp to both hTDO and XcTDO has been used to interpret these results. It is suggested that Compound II in TDO has a different spectrum or that the rate-limiting step is altered and an alternative catalytic intermediate accumulates. Crystal trials have been conducted for hIDO and hTDO, with some conditions producing micro-crystals. The structure of XcTDO in complex with potassium cyanide and L-Trp was solved. The binding mode of L-Trp within the distal pocket does not correlate with the L-Trp binding mode in the published ferrous XcTDO- L-Trp binary complex structure. Oxidation of L-Trp by ferric TDO without the addition of reducing agent was investigated. The results suggest the recruitment of hydrogen peroxide from solution to activate ferric heme. A summary of the mechanistic information gathered from all of the above experiments is presented.
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Varvel, Hallie Johnson. « Tryptophan Supplementation During Lactation on Sow Productivity ». OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2551.
Texte intégralRésumé :
The objective of this study was to examine the potential effects of supplementing excess crystalline tryptophan (trp) in the lactation diets of sows. Sixty-one sows of varying parity were fed either a control diet (0.26% trp) or a treatment diet with an extra two grams of tryptophan (0.30% trp). Over the 28 day lactation period utilized by the production site, sow and litter performance were recorded. Sow performance was measured by backfat loss, blood urea nitrogen, milk composition, return to estrus, wean to estrus interval, and conception rate. Litter performance was measured as average weaning weight, number weaned, and pre-wean mortality. The control and treatment groups were further subdivided by parity for statistical analysis. Sows of parity one and two were classified as primiparous, while sows of parity three or more were classified as multiparous. There were no significant differences (P≤0.05) between the control and treatment diets even with regards to parity groups. There was one trend (0.05
0.10) in which treatment multiparous sows had higher litter weaning weight (P=0.055) than the control multiparous sows. In summary, these results indicate that increasing the tryptophan level in this lactation diet by two grams did not significantly influence sow or litter performance.
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Boshra, Mohamed [Verfasser]. « Experimente zum proteomweiten Austausch von L-Tryptophan in Escherichia coli gegen 4-Aza- und 4-Fluor-Tryptophan / Mohamed Boshra ». Berlin : Freie Universität Berlin, 2018. http://d-nb.info/1155167198/34.
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Antunes, Ana Paula Martins. « An investigation into the antioxidative potential and regulatory aspects of liver tryptophan 2,3-dioxygenase by tryptophan and related analogues ». Thesis, Rhodes University, 1998. http://hdl.handle.net/10962/d1004070.
Texte intégralRésumé :
The amino acid, tryptophan, obtained through dietary means, is metabolised by the enzymes tryptophan 2,3-dioxygenase (TDO), indoleamine 2,3-dioxygenase (IDO) and tryptophan hydroxylase. All the enzymes have an effect on circulating tryptophan levels, especially TDO, since it is the major site of tryptophan catabolism in the liver and results in the production of kynurenine metabolites, viz. kynurenine, kynurenic acid, 3-hydroxyanthranilic acid and quinolinic acid. Extrahepatically, IDO is responsible for the synthesis of the kynurenine metabolites. Tryptophan 2,3-dioxygenase and IDO activity is increased by hormones or substrates such as tryptophan, and inflammation, in the case of IDO. Tryptophan availability for serotonin (5-HT) synthesis by the enzyme tryptophan hydroxylase is primarily dependent on TDO activity. A study was attempted in order to ascertain whether any of the endogenous metabolites of the kynurenine and serotonergic pathways would be able to inhibit TDO activity. Results showed that although the kynurenines had no effect, the indoleamines, except for the indoleacetic acids, were able to reduce TDO activity. 6-Methoxy-2-benzoxazolinone (6-MBOA), a structural analogue to melatonin, was the most potent inhibitor with a reduction in activity of 55 % compared with the control. The pineal gland in the rat brain has been shown to have the highest IDO activity. With induction, the kynurenine metabolite concentrations of kynurenic acid and quinolinic acid are increased. The effects of both compounds were determined on the serotonergic pathway. Although kynurenic acid produced no significant effect, quinolinic acid significantly reduced N-acetylserotonin and melatonin synthesis at concentrations of lOJLM and 100 JLM respectively. Many authors have implicated oxygen derived species as causative agents in the important neurodegenerative disorders such as Parkinson's and Huntington's disease. Increased radical generation and lipid peroxidation have been suggested to be responsible for the toxic destruction of neurons, especially in the brain because of its high lipid content and oxygen demand. The brain is therefore vulnerable to oxidative attack. During inflammatory diseases, IDO is induced with a resultant increase in kynurenines. This study was also an attempt at determining the effect of kynurenines on lipid peroxidation. All metabolites of the kynurenine pathway were able to induce lipid peroxidation significantly. The antioxidative potential of various tryptophan analogues, viz. serotonin, melatonin and 6-methoxy-2-benzoxazolinone, was determined using quinolinic acid-induced lipid peroxidation. Serotonin, melatonin and 6-MBOA were able to significantly reduce quinolinic acid-induced lipid peroxidation.
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DeFelippis, Michael Rosario. « The redox potentials of the tyrosine and tryptophan radicals and long-range electron transfer between tyrosine and tryptophan in peptides / ». The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487678444257431.
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Salimi, Elizei Sanam. « Anti-inflammatory role of IDO and tryptophan metabolites ». Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59120.
Texte intégralRésumé :
Inflammation is essential to the establishment of homeostasis following injury and inflammatory cell and the cytokine network associate with tissue repair. However, sometimes inflammation can cause further inflammation; it can become self-perpetuating. One of the many possibilities of prolonged secretion of cytokines and growth factor is autoimmunity and delay in wound closure. The current anti-inflammatory treatment modalities vary however their adverse effects are common. Here we asked the question of whether Kynurenine (Kyn), one of the tryptophan (Trp) metabolite, could modulate the inflammation by altering the profile of the key pro-inflammatory cytokines as well as the proliferation of immune cells. We showed that Kyn treatment significantly reduced some pro-inflammatory cytokines and chemokines such as IL-17, IL-2, CXCL-9 and CXCL-10 in ConA⁺ Kyn-treated splenocytes. To validate our findings in a wound healing model, we also showed that topical application of Kyn cream resulted in fewer infiltration of CD3⁺ T cells at wound site. Further, in this study we used kynurenic acid (KynA) instead of Kyn as KynA is the end product and safer metabolites in the kynurenine pathway. The emphasis was given in evaluating the effect of KynA on expression of IL-17/IL-23 axis which has recently been identified to be very important in the immunopathogenesis of autoimmune diseases and inflammation such as psoriasis. Our findings have shown that KynA can modulate the frequency of IL-23 and IL-17 by DCs and CD4⁺ cells. Moreover, we showed that KynA suppresses the production of IL-23 in DCs through GPCR35 activation. We then evaluated the therapeutic use of intra-lesional injection of IDO-expressing fibroblasts, as a source of Kyn and KynA production in psoriasis, which is one of the most common recurrent chronic inflammatory diseases of the skin. The findings of this work demonstrated that IDO-expressing cells significantly improved thickness, erythema, and scaling scores in skin psoriatic like condition. Moreover, IDO-expressing fibroblasts reduce infiltration of IL-17⁺ CD4⁺, IL-17⁺ γδ⁺ T cells, IL-23⁺-activated dendritic cells and granulocytes in skin psoriatic like condition. The findings presented in this thesis collectively prove the potent local immunosuppressive activity of IDO-expressing dermal fibroblast and tryptophan metabolites in skin inflammatory conditions.Medicine, Faculty of
Graduate
27
Davis, Kevin. « An analysis of models of the tryptophan operon ». Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19269.
Texte intégralRésumé :
Though the tryptophan operon has received a fair amount of experimental study over recent decades, modeling e?orts have been relatively few and disparate in some of their conclusions regarding the behavior of the operon. We consider a selection of existing models of the tryptophan operon and analyze them from the standpoints of stability, response to periodic signals in the biochemistry, and existence of attracting invariant manifolds in the model state space. We ?nd that the stability properties of these models may depend greatly upon small changes in parameters that are in keeping with updated experimental data. Further, we show the ability of the tryptophan operon to act as a classical band-pass ?lter to periodic ?uctuations ostensibly caused by the periodic nature of the cell cycle. Finally, a functional iteration technique for the approximate computation of attracting invariant manifolds is presented and the manifold for one of the models is computed.Bien que l'opéron de tryptophane ait fait l'objet d'un nombre d'essais expérimentaux considérables dans les dernières décennies, les e?orts dans la modélisation ont été rel- ativement peu et disparates quant à leurs conclusions concernant le comportement de l'opéron. Nous considérons un choix de modèles existants de l'opéron de tryptophane et les analysons des points de vue de leur stabilité, de leur réponse aux signaux périodiques en biochimie, et de l'existence d'attractions de variétés invariantes dans l'espace d'états du modèle. Nous constatons que les propriétés de stabilité de ces modèles peuvent dépendre considérablement de petits changements des paramètres qui sont en accord avec des données expérimentales mises à jour. De plus, nous montrons la capacité de l'opéron de tryptophane à agir comme ?ltre passe-bande classique aux ?uctuations périodiques en apparence provoquées par la nature périodique du cycle cellulaire. En conclusion, une technique fonctionnelle d'itération pour le calcul approximatif de l'attraction de variété invariante est présentée et la variété pour un des modèles est calculée. fr
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Wise, William Robert. « Synthetic chemistry for tryptophan tryptophylquinone like enzyme cofactors ». Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/10072.
Texte intégralRésumé :
This thesis describes studies on the synthesis of model compounds based on the tryptophan tryptophanyl quinone (TTQ) cofactor designed to probe the mechanism by which it catalyses primary amine oxidation and the role of the enzyme in assisting the TTQ-facilitated reaction. This project has begun to explore ways of investigating the mechanistic landscape going from small molecule ortho-quinone catalysis through to the corresponding enzymatic reaction to address the proposal that enzyme environment is directly involved in the catalytic activity of the TTQ moiety by facilitating a process known as quantum tunnelling and to determine at what point does the catalytic mechanism 'swap' from a classical one to a mechanism involving quantum tunnelling? The principal goal was therefore to establish a synthetic route to novel amino acid building blocks that contained appropriate functionality that could be converted into the key ortho-quinone unit that would mimic TTQ. Such fragments required suitable protecting groups to allow their incorporation into peptide and protein domains. This report describes exploration of two synthetic routes to such molecules, both routes utilising 4-methylphenol that, once modified, incorporates the key ortho-quinone unit. One approach is the synthesis of a novel TTQ-like amino acid that would allow for insertion into a peptide using well documented procedures. This thesis details a variety of different synthetic approaches to the preparation of such a molecule, including problems in coupling the amino acid moiety with the quinone moiety and utilisation of a range of protecting groups in an attempt to overcome these problems. An alternative approach is also explored involving the synthesis of an ortho-quinone cassette that incorporates either alkyne or azide functionality and utilisation of the relatively new field of copper-catalysed click chemistry to insert this unit into an enzyme containing a non-natural amino acid with an alkyne or azide-containing side chain. Again details of a variety of different routes involved in attempting to produce such a molecule are given and although the target molecule was not produced a model system was successfully developed and inserted into an alkyne-containing amino acid.
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Haule, Ambrose Francis. « Design of tryptophan analogues as novel tryptanocidal drugs ». Thesis, University of Sunderland, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277923.
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Swift, Simon. « Tryptophan synthase : a model for protein/protein interaction ». Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303962.
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Thackray, Sarah J. « Enzymatic and mechanistic studies into tryptophan 2,3-dioxygenase ». Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/11458.
Texte intégralRésumé :
Tryptophan 2,3-dioxygenase (TDO) from Xanthomonas campestris (xcTDO) is a highly specific heme-containing enzyme from a small family of homologous enzymes, which includes indoleamine 2,3-dioxygenase (IDO). TDO contains a histidine residue (histidine 55) in its active site, which hydrogen bonds to the indole nitrogen atom of L-tryptophan, and could function as an active site base. In this study we attempt to resolve the question of whether an active site base is necessary for catalytic activity, to which end, two complementary strategies, based on the active-site structure have been applied. Firstly, active-site mutants were studied, where histidine 55 was replaced by alanine or serine (H55A and H55S). The crystal structures of the H55A and H55S mutant forms were determined to 2.15 Å and 1.90 Å resolution respectively, in binary complexes with L-tryptophan. These structural data, in conjunction with potentiometric and kinetic studies, reveal that histidine 55 is not essential for turnover, but greatly disfavours the mechanistically unproductive binding of L-tryptophan to the oxidized enzyme, allowing control of catalysis. The second strategy utilises 1-methyl tryptophan. Our studies reveal that whilst 1-methyl tryptophan is not a substrate for TDO, and is not an inhibitor of its action, the active site mutants H55A and H55S can deoxygenate 1-methyl tryptophan. These catalytic differences are explained by comparison of the active sites of the enzymes, and support the proposal that a catalytic base is not necessary for enzymatic activity. In addition, these data provide new insight into the future of 1-methyl tryptophan as an inhibitor of IDO activity in cancer treatments.
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Zholudov, Yu, N. Lysak et G. Xu. « Electrochemiluminescence in Tryptophan / Tetraphenylborate System for Biosamples Assay ». Thesis, ISBC, 2018. http://openarchive.nure.ua/handle/document/5793.
Texte intégralRésumé :
L-tryptophan is one of the most important essential amino acids which role in the human body is invaluable. It participates in maintaining of nitrogen balance in metabolism, in the synthesis of muscle proteins, enzymes, antibodies of the immune system and other biologically active substances. Thus the development of reliable methods for quantitative determination of this compound in biolsamples, foods and medicines is an actual task for today.
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Zhang, Luyuan. « Ultrafast Protein Hydration Dynamics Probed by Intrinsic Tryptophan ». The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276524825.
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Ummadi, Madhavi. « Tryptophan Catabolism in Brevibacterium linens BL2 ». DigitalCommons@USU, 2002. https://digitalcommons.usu.edu/etd/5501.
Texte intégralRésumé :
Recent studies suggest aromatic amino acid catabolism by starter lactococci and flavor adjunct bacteria have a significant impact on off-flavor development during Cheddar cheese ripening. We hypothesized that a flavor adjunct bacterium, Brevibacterium linens BL2, produces off-flavor compounds from aromatic amino acid metabolism that will have a detrimental impact on cheese flavor.
The mechanism of tryptophan (Trp) catabolism in Brevibacterium linens BL2, was investigated in a chemically defined medium during incubation in laboratory conditions (no carbohydrate, pH 6.50, 220 rpm, 25°C) and cheese-like conditions (no carbohydrate, 4% NaCl, static incubation, l5°C). In laboratory conditions, metabolic studies and enzyme assays confirmed that Trp was converted to kynurenine and anthranilic acid. However, cells incubated in cheese-like conditions did not utilize Trp, indicating that these enzymes are not likely to be involved in formation of Trp compounds associated with off-flavors in Cheddar cheese.
In an attempt to verify the metabolic activity of the cells during incubation by monitoring the amino acid metabolism in chemically defined medium inoculated with B. linens BL2, a capillary electrophoresis-laser-induced fluorescence method was developed that could separate, detect, and quantitate 18 amino acids within 38 min. The data indicated that B. linens BL2 was metabolically active. Presumably, the cells will be metabolically active and metabolize amino acids in cheese as well.
The ability to determine the Trp metabolic activity of B. linens BL2 in cheese, and to quantify Trp catabolic compounds in cheese during ripening, requires a quantitative extraction procedure. An analytical method was developed to extract and quantify aromatic amino acids and Trp catabolites from cheese using capillary electrophoresis. Methanol was used to extract Cheddar cheese made with Lactococcus lactis S3 alone and in combination with B. linens BL2 to quantitatively determine the influence of BL2 on the occurrence of aromatic catabolites. All cheeses contained aromatic amino acids, indole acetic acid, and indole. The concentration and time taken for development of these compounds were significantly decreased or delayed by the addition of B. linens BL2. After 6 months of aging, the concentrations of Trp catabolites were significantly lower in cheese made with B. linens BL2. Addition of BL2 did not directly contribute to off-flavors derived from Trp catabolism in Cheddar cheese. Therefore, the hypothesis was rejected.
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Frith, Kelly-Anne. « Polymers, catalysts and nanostructures a hybrid approach to biomolecule detection ». Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1004039.
Texte intégralRésumé :
The main goals in electroanalytical sensing are towards improved sensitivity and selectivity, or specificity, of an analyte. There are several approaches to achieving these goals with the main approach being modification of an electrode surface with synthetic or natural catalysts (enzymes), polymers and also utilisation of nanostructured materials. At present, there is a strong movement towards hybrid sensing which couple different properties of two or more surface modification approaches. In this thesis, a range of these surface modifications were explored for analysis and detection of two main analytes: the amino acid, tryptophan (Trp); and, the neurotransmitter, dopamine (DA). Specifically, this thesis aimed to utilise these methods to enhance the sensitivity and selectivity for Trp over an interferent, the indoleamine, melatonin (Mel); and, DA over the vitamin, ascorbic acid (AA). For Trp detection, immobilisation of an enzyme, Tryptophanase (Trpase) resulted in poor selectivity for the analyte. However, enhanced sensitivity and selectivity was achieved through pH manipulation of the electrolyte medium at a Nafion®-modified electrode surface for both Trp and Mel. At pH 3.0, the Mel and Trp anodic peak potentials were sufficiently resolved allowing for an LOD of 1.60 and 1.62 nM,respectively, and permitting the accurate analysis of Trp in a dietary supplement containing Mel. Multi-walled carbon nanotubes (MWCNTs) suspended in Nafion® exhibited further increases in the signal responses of these analytes at pH 3.0 and 7.4 with minimal change in the resolution of the anodic peaks. A lower sensitivity was, therefore, observed at the Nafion® and MWCNT modified electrode compared to the Nafion®-modified electrode at pH 3.0 with LODs of 0.59 and 0.80 nM exhibited for Trp and Mel, respectively. Enhanced selectivity for Trp in the presence of Mel can be achieved with MWCNTs in the presence of metallotetrasulphonated phthalocyanines (MTSPcs) particularly at pH 3.0, owing to cation exchange effects. However, the lack of sensitivity towards Trp, and even Mel, at this CoTSPc and MWCNT modified electrode remains a drawback. For DA, detection at the MWCNT and Nafion® surface resulted in improved sensitivity over that of both the bare electrode (613.0 nM) and the Nafion® modified electrode (1045.1 nM) with a calculated LOD of 133.9 nM at this layer. Furthermore, improvements in the selectivity of DA were achieved at the Nafion® and MWCNT modified electrode as exclusion of AA (150 μM) was achieved. At the MWCNT and CoTSPc surface, AA was excluded up to 130 μM with sensitivity for DA extending as low as 14.3 nM, far greater than observed for Trp and Mel. These concentrations are well within physiological concentration ranges and represent the most significant solution yet in terms of AA exclusion and enhanced sensitivity for DA. An examination of the surface layering by impedance spectroscopy and atomic force microscopy indicates that the success of the hybrid sensor utilising CoTSPc and MWCNTs lay in improved dispersion of MWCNTs and improved electron transfer kinetics, facilitated by the net charge of the materials present. This thesis, thus, showed the utility of a judicious selection of synthetic and biological catalysts, polymers and carbon nanomaterials towards a hybrid approach to the electrochemical sensing of Trp, Mel, DA and AA with focus on sensitivity and selectivity of these analytes.
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McElroy, Craig Alan. « Dynamics and function mechanistic studies of the gene regulatory proteins TRAP and anti-TRAP / ». Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1111429539.
Texte intégralRésumé :
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 327 p.; also includes graphics (some col.) Includes bibliographical references (p. 315-327). Available online via OhioLINK's ETD Center
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Toyn, Jeremy H. « The selection and study of mutants of the yeast Saccharomyces cerevisiae that are defective for translocation of proteins into the endoplasmic reticulum ». Thesis, Open University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327843.
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Lysek, Nicola. « Tryptophan-Abkömmlinge in wirbellosen Meerestieren Isolierung, Struktur und Funktion / ». [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965429881.
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Tusell, Jose Ramon. « Computation of tryptophan fluorescence quenching by amide and histidine ». Diss., Montana State University, 2011. http://etd.lib.montana.edu/etd/2011/tusell/TusellJ1211.pdf.
Texte intégralRésumé :
Tryptophan fluorescence quantum yield is widely used to follow protein folding for the villin headpiece subdomain (HP-35) and a synthetic peptide Ac-W-(A) ₃ -H + -NH ₂ (WH5). These biopolymers have a histidine residue, which is a potent quencher of tryptophan fluorescence, positioned four amino acids away from tryptophan. Experiments assumed that when folding occurs the fluorescence of tryptophan will be quenched by histidine due to the formation of an alpha helix. The reliability of folding and unfolding rate constants determined by tryptophan fluorescence has been called into question by several computational studies. A method to calculate the electron transfer matrix element was developed for different donor/acceptor systems. This method shows that the electron transfer matrix element is sensitive to orientation at close distances and that it does not follow a simple exponential decay with distance. This thesis improved the methods developed by Callis and coworker by conducting 100 ns long simulations for single tryptophan proteins and by modifying the calculation of the fluorescence quantum yield to account for heterogeneity in the calculated electron transfer rates. In addition the method was extended to calculate electron transfer rate constants for histidine quenching by conducting 1microsecond long simulations of HP-35 and WH5. Calculated tryptophan fluorescence quantum yields for the single tryptophan proteins show better agreement with experiment than was previously reported. Simulations for HP-35 and WH5 indicate that the ability of histidine to quench the fluorescence of tryptophan is surprisingly controlled by the energy gap dependence on the distance that separates them. The energy gap dependence on this distance arises from water solvation around histidine. At large distances this solvation decreases the ability of histidine to accept an electron from tryptophan. Different tryptophan/histidine rotamers control this distance. Even when HP-35 is completely folded much of the time histidine does not quench tryptophan fluorescence contrary to the idea that histidine is only close when HP-35 is folded. The calculated fluorescence quantum yield is sensitive to the distribution of close and far conformations and the rate of exchange between these two conformations. This sensitivity gives credibility to the folding/unfolding rates derived from tryptophan fluorescence quantum yields.
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Phillips, Susan R. « Spectroscopic investigation of tryptophan microenvironments in bovine lens proteins ». Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/32973.
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Regoli, Martine. « Acute tryptophan depletion in heavy 3,4-methylenedioxymethamphetamine (MDMAecstasy) users ». Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80860.
Texte intégralRésumé :
3,4-methylenedioxymethamphetamine (MDMA/ecstasy) is a serotonin neurotoxin in animals. Human MDMA abusers exhibit evidence of disturbed serotonin transmission. Altered serotonergic neurotransmission in MDMA abusers might underline susceptibility to developing depressed mood. The acute tryptophan depletion (ATD) challenge was used to study altered serotonin levels in MDMA abusers. Sixteen MDMA abusers and nineteen age- and gender-matched controls were tested. In a double-blind crossover study, subjects ingested a 100g amino acid mixture with or devoid of tryptophan. Mood was measured before and after the ingestion of the amino acid, a total of three times throughout the day. Impulsivity was measured with the Go/No-Go task. ATD lowered mood (p < 0.01) and increased anxiety (p < 0.05) in female MDMA abusers. The present design does not permit a distinction between effects of MDMA use or a pre-existing trait. If the effects are due to neurotoxicity, they could reflect MDMA abuse alone or an effect of a combination of drugs.
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Zholudov, Yu. « Electrogenerated chemiluminescence in tryptophan / tetraphenylborate system for biosamples assay ». Thesis, КрНУ, 2018. http://openarchive.nure.ua/handle/document/7523.
Texte intégralRésumé :
In this work the results of study of electrochemiluminescence in the system tryptophan / co-reatant tetraphenylborate and analysis of the possibility of its use for measuring the content of the amino acid tryptophan in biological samples are presented.
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Wohlgamuth-Benedum, Jessica M. « MODIFICATION AND EDITING IN MITOCHONDRIAL TRYPTOPHAN tRNA OF TRYPANOSOMES ». The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1245097409.
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Quiel, Juan Antonio. « The tryptophan biosynthetic pathway in Arabidopsis and its regulation ». Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3068200.
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Smolen, Gromoslaw A. « Regulation of the tryptophan biosynthetic pathway in Arabidopsis thaliana ». Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3068214.
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Kad, Neil M. « Probing the functional and conformational dynamics of the chaperonins GroEL and GroES ». Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265326.
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Dacko, Christopher Andrew. « The synthesis of tryptophan derivatives, 2- and/or 3-substituted indoles, progress toward dilemmaones A-C, and synthetic studies towards fistulosin via palladium-catalyzed reductive N-heteroannulation ». Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10403.
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Thesis (Ph. D.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains xxvi, 324 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 186-198).
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