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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

On the inactivation of the catecholase activity of tyrosinase during the enzymatic oxidation of certain substituted catechols

Roth, Lloyd J. January 1944 (has links)
Diss. - Columbia University.
22

The kinetics of the reaction inactivation of tyrosinase during its catalysis of the aerobic oxidation of catechol

Asimov, Isaac, January 1948 (has links)
Thesis--Columbia University. / Vita. Bibliography: p. 65-66.
23

On the mechanism of the reaction involved in the aerobic oxidation of catechol when catalyzed by the enzyme, tyrosinase ...

Soloway, Saul, January 1941 (has links)
Thesis (Ph. D.)--Columbia University, 1942. / Vita. Bibliography: p. 14.
24

The oxidation of catechol-type substrates by tyrosinase

Cushing, Merchant Leroy, January 1941 (has links)
Thesis (Ph. D.)--Columbia University, 1941. / Vita. Bibliography: p. 20.
25

Doppelresonanzspektroskopie an biologisch relevanten Systemen

Plützer, Christian. January 2002 (has links) (PDF)
Düsseldorf, Universiẗat, Diss., 2003.
26

Biocatalytic and biomimetic studies of polyphenol oxidase

Burton, Stephanie Gail January 1994 (has links)
Mushroom polyphenol oxidase (EC 1.14.18.1) was investigated to determine its potential for application as a biocatalyst in the synthesis of o-quinones, in organic medium. In order to determine the kinetic properties of the biocatalyst, a system was devised which comprised an immobilised polyphenol oxidase extract, functioning in chloroform. The system was hydrated by the addition of buffer. A simple method for the consistent measurement of reaction rates in this heterogenous system was designed and used to obtain detailed enzyme kinetic data relating to optimisation of reaction conditions and substrate specificity. The aqueous content of the system was optimised using p-cresol as a substrate. A crude, immobilised extract of Agaricus bisporus was used to hydroxylate and oxidise a range of selected p-substituted phenolic substrates, yielding, as the sale products, o-quinones. These products were efficiently reduced to catechols by extracting the reaction mixtures with aqueous ascorbic acid solution. The biocatalytic system was also successfully utilised to produce L-DOPA, the drug used to treat Parkinson's disease, from L-acetyl tyrosine ethyl ester (ATEE). Michaelis-Menten kinetics were used to obtain apparent Km and V values with respect to the selected phenolic substrates, and the kinetic parameters obtained were found to correlate well with the steric requirements of the substrates and with their hydrophobicity. In the course of the investigation, a novel ¹H NMR method was used to facilitate measurement of the UV molar absorption coefficients of the o-quinones in reaction mixtures, thus avoiding the necessity to isolate these unstable, water-sensitive products. The biocatalytic system was extended to a continuous process, in which the immobilised enzyme was shown to function successfully in the chloroform medium for several hours, with high conversion rates. Modifications, involving partial purification and the addition of a surfactant, were investigated to determine their effect on the kinetic parameters. The results obtained using partially purified enzyme indicated that the removal of extraneous protein and/or melanoid material lead to a reduced capacity for conversion of sterically demanding substrates. The addition of the anionic detergent, sodium dodecyl sulphate (SOS), enhanced the ability of the biocatalyst to bind and oxidise sterically demanding substrates. These effects are attributed to changes in the polar state of groups within the protein binding pocket, which result in altered flexibility and hydrophobicity. Computer modelling of several biomimetic dinuclear copper complexes also indicated the importance of flexibility for effective biocatalysis. Novel binuclear copper (II complexes, containing a flexible biphenyl spacer and imidazole or benzimidazole donors, were prepared and analysed using NMR, UV, AA and cyclic voltammetric techniques. The complexes were also shown, in a detailed kinetic study, to mimic the catecholase activity of polyphenol oxidase by oxidising 3,5-di-tertbutylcatechol, and to catalyse the coupling of the phenolic substrate 2,4-di-tert-butylphenol. However, the complexes were apparently too flexible to react with smaller substrates. These biomimetic complexes provided valuable insights into the nature of the dinuclear copper binding site.
27

Kinetics of the laccase-catalyzed oxidation of aqueous phenol

Soegiaman, Selvia Kurniawati. January 2006 (has links)
No description available.
28

Biocatalysis of tyrosinase in organic solvent media using phenolic substrate models

Bao, Haihong. January 1999 (has links)
No description available.
29

Acclimation of mixed cultures for phenol biodegradation

Phillips, David Gray, 1949- January 1988 (has links)
Experiments were conducted to examine the cause of lag-phase growth during phenol degradation by mixed microbial cultures that had been acclimated to one of four substrates. Four aerated Imhoff cones were inoculated with wastewater sludge and fed one of four substrates: acetate, egg albumin, vegetable oil, or phenol. Inocula from these cones were injected into batch reactors containing phenol. Time-dependent growth was measured by two methods: most probable number (MPN) and epifluorescence microscopy (EM). The MPN technique was used to distinguish two cell concentrations: total cells and a phenol-degrading community within the total; EM was also used to count total cells. The results indicated that a lag in phenol utilization for all cultures, except the phenol-acclimated cultures, was a result of growth of a phenol-degrading subpopulation, and not due to enzyme induction of the existing population. Similar experiments were conducted using 2,4-dichlorophenol (2,4-DCP), which resulted in no growth and no degradation of 2,4-DCP.
30

Interactions between microalgae and chlorophenols in liquid culture

Olivier, Sandrine January 2001 (has links)
No description available.

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