Increasing demand for chiral technology in industry has led to the rapid development of catalysts for enantioselective processes. In this respect biocatalysts are of particular interest due to their excellent regio- and stereo- selectivity and their ability to work under mild conditions. The development of catalysts for the selective oxidation of alcohols to aldehydes and ketones represents a major challenge in organic synthesis. Previous work showed that a variant of the enzyme galactose oxidase (GOase) was capable of oxidising a wide range of chiral secondary alcohols with high enantioselectivity. The aim of this work is to develop new applications for this variant. Two new stereoselective processes have been developed employing this variant: 1. Enzymatic desymmetrisation of proatropisomeric diaryl ethers and biaryls. Atropisomers are stereoisomers resulting from restricted rotation about an axis, where the rotational barrier is high enough for isolation of the conformers. Desymmetrisation by GOase has allowed the production of atropisomers with enantiomeric excess (ee) up to 99% in good yields. An alternative approach based upon asymmetric reduction of the corresponding dialdehyde using ketoreductases (KREDs) has also been explored. 2. Deracemisation of racemic secondary alcohols by a combination of enzyme and transition metal catalysts. Deracemisation is a method for the production of enantiopure compounds starting from racemic substrates. Combination of the enzyme GOase and a transition metal catalyst has allowed the production of a single enantiomer of a number of secondary alcohols from the corresponding racemic mixture (ee > 99%, yield > 98%). Primary amides are widely applied in the polymer industry. They are produced in large quantities each year. An efficient solvent-free process (yield > 90%) for the production of erucamide has been developed employing immobilised Candida antarctica Lipase B (CALB, Novozym® 435 ) under mild conditions (solid ammonia source, 90 °C).

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No description available.

A β-galactosidase (E.C 3.2.1.23) é uma das enzimas mais empregadas na indústria de alimentos sendo utilizada na hidrólise da lactose. Neste trabalho foram utilizadas duas metodologias para imobilização desta enzima. Na primeira delas foi empregado como suporte um material híbrido à base de sílica que possui um grupo orgânico catiônico covalentemente ligado. A adsorção da enzima a este material apresentou eficiência que variou de 74 a 53% com o aumento da quantidade de enzima aplicada ao suporte. A baixa estabilidade térmica da enzima imobilizada obtida e as prováveis fracas interações envolvidas na sua adsorção a este suporte podem explicar o decréscimo de atividade observada durante as sucessivas bateladas de hidrólise da lactose. Na primeira batelada o grau de hidrólise foi de 90,9% e no final da última batelada (4ª), a enzima foi capaz de converter apenas 13% do substrato. A segunda metodologia utilizada foi imobilização covalente da enzima em um filme de celulose/líquido iônico modificado com uma poliamina e ativado com glutaraldeído. A presença da poliamina foi confirmada por análises de infravermelho. Após a imobilização, a enzima reteve 60% de sua atividade inicial. Bons resultados de hidrólise da lactose em batelada foram obtidos tanto a 7ºC como a 35ºC e foi possível reutilizar a enzima imobilizada por 16 ciclos consecutivos, a 7ºC, sem mudanças significativas na atividade enzimática. O valor de Km para a enzima imobilizada no material híbrido à base de sílica foi de 9,17 mM e para a enzima imobilizada nos filmes de celulose foi de 11,22 mM, ambos apresentaram um acréscimo quando comparados ao Km enzima livre (1,25 mM), devido à dificuldade de acesso do substrato ao sítio ativo da enzima. Não houve mudança no pH e temperatura ótimos da enzima imobilizada em relação à enzima livre em nenhum dos métodos testados. / β-galactosidase (E.C 3.2.1.23) is the most widely used enzymes in the food industry and its employed in the lactose hydrolysis process. In this study, two methodologies were used to test their immobilization. In the first, the enzyme was immobilized by adsorption in one silica based hybrid material that contains a cationic organic group covalently linked. The efficiency of immobilization showed a decrease of 74 to 53% by increasing the protein load applied to the support. The low thermo stability of the immobilized enzyme and the probable weak interactions involved in their adsorption, could explain the decrease in enzyme activity observed in the successive batch hydrolysis of lactose. In the first run, the degree of lactose hydrolysis was 90.9% and, at the end of the last run (4th), the enzyme was able to convert only 13% of the substrate. The second methodology used was the covalent immobilization of the enzyme on a cellulose/ionic liquid film, modified with a polyamine and activated using glutaraldehyde. The presence of a polyamine was confirmed by infrared analysis. After immobilization, the enzyme retained 60% of its initial activity. Highly efficient lactose conversion was achieved in a batch process at 7ºC and 35ºC and was possible to reuse the immobilized enzyme in 16 repeated cycles, at 7ºC, without any drastic decrease in enzyme activity. Km value for the immobilized enzyme in silica based hybrid material was 9.17 mM and for the enzyme immobilized in the film of cellulose/ionic liquid was 11.22 mM, both showing an increase compared with the Km value for free enzyme (1.25 mM), due to the difficulty of access of the substrate to the active sites of the enzyme. The immobilized enzyme did not show any changes in the optimal pH and temperature when compared to the free enzyme in both methods tested.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Química / Made available in DSpace on 2013-07-16T02:17:49Z (GMT). No. of bitstreams: 0 / No presente trabalho, foram sintetizados e caracterizados novos complexos mononucleares de cobre(II), zinco(II), manganês(III), gálio(III), índio(III) e ferro(III). As estruturas cristalinas dos complexos 1, 2, 3, 5, 7, 8 e 12 foram obtidas através da análise de monocristais dos respectivos complexos pelo método de difração de raios X. Praticamente todos os complexos apresentam um ambiente de coordenação tetragonalmente distorcido para os íons metálicos, sendo a geometrias observadas nos complexos de cobre muito similares as do sítio ativo da enzima GAO. Através da oxidação dos complexos 1 a 10, via processos químicos e/ou eletroquímicos foram obtidos complexos radicalares (metalo-fenoxil) do tipo [MII(HL)]2+", [MII(HL)]3+"", [MII(L)]+", [MII(L)]2+"", [MIII(L)]2+", [MIII(L)]3+"" e [MnIV(L)]4+"", os quais foram devidamente caracterizados pelas espectroscopias de UV-VIS, RPE, assim como técnicas espectroeletroquímicas e coulométricas. As propriedades eletroquímicas e eletrônicas dos complexos metalo-fenoxil apresentam bastante semelhança com às encontradas na GAO e em outros complexos modelo metalo-fenoxil, o que coloca estes complexos como bons modelos funcionais para a enzima GAO e para espécies metalo-radicalares. Alguns dos complexos metalo-fenoxil obtidos são moderadamente estáveis à temperatura ambiente e mostraram-se efetivos na oxidação do substrato 2,4,6-tri-terc-butilfenol.

A β-galactosidase (E.C 3.2.1.23) é uma das enzimas mais empregadas na indústria de alimentos sendo utilizada na hidrólise da lactose. Neste trabalho foram utilizadas duas metodologias para imobilização desta enzima. Na primeira delas foi empregado como suporte um material híbrido à base de sílica que possui um grupo orgânico catiônico covalentemente ligado. A adsorção da enzima a este material apresentou eficiência que variou de 74 a 53% com o aumento da quantidade de enzima aplicada ao suporte. A baixa estabilidade térmica da enzima imobilizada obtida e as prováveis fracas interações envolvidas na sua adsorção a este suporte podem explicar o decréscimo de atividade observada durante as sucessivas bateladas de hidrólise da lactose. Na primeira batelada o grau de hidrólise foi de 90,9% e no final da última batelada (4ª), a enzima foi capaz de converter apenas 13% do substrato. A segunda metodologia utilizada foi imobilização covalente da enzima em um filme de celulose/líquido iônico modificado com uma poliamina e ativado com glutaraldeído. A presença da poliamina foi confirmada por análises de infravermelho. Após a imobilização, a enzima reteve 60% de sua atividade inicial. Bons resultados de hidrólise da lactose em batelada foram obtidos tanto a 7ºC como a 35ºC e foi possível reutilizar a enzima imobilizada por 16 ciclos consecutivos, a 7ºC, sem mudanças significativas na atividade enzimática. O valor de Km para a enzima imobilizada no material híbrido à base de sílica foi de 9,17 mM e para a enzima imobilizada nos filmes de celulose foi de 11,22 mM, ambos apresentaram um acréscimo quando comparados ao Km enzima livre (1,25 mM), devido à dificuldade de acesso do substrato ao sítio ativo da enzima. Não houve mudança no pH e temperatura ótimos da enzima imobilizada em relação à enzima livre em nenhum dos métodos testados. / β-galactosidase (E.C 3.2.1.23) is the most widely used enzymes in the food industry and its employed in the lactose hydrolysis process. In this study, two methodologies were used to test their immobilization. In the first, the enzyme was immobilized by adsorption in one silica based hybrid material that contains a cationic organic group covalently linked. The efficiency of immobilization showed a decrease of 74 to 53% by increasing the protein load applied to the support. The low thermo stability of the immobilized enzyme and the probable weak interactions involved in their adsorption, could explain the decrease in enzyme activity observed in the successive batch hydrolysis of lactose. In the first run, the degree of lactose hydrolysis was 90.9% and, at the end of the last run (4th), the enzyme was able to convert only 13% of the substrate. The second methodology used was the covalent immobilization of the enzyme on a cellulose/ionic liquid film, modified with a polyamine and activated using glutaraldehyde. The presence of a polyamine was confirmed by infrared analysis. After immobilization, the enzyme retained 60% of its initial activity. Highly efficient lactose conversion was achieved in a batch process at 7ºC and 35ºC and was possible to reuse the immobilized enzyme in 16 repeated cycles, at 7ºC, without any drastic decrease in enzyme activity. Km value for the immobilized enzyme in silica based hybrid material was 9.17 mM and for the enzyme immobilized in the film of cellulose/ionic liquid was 11.22 mM, both showing an increase compared with the Km value for free enzyme (1.25 mM), due to the difficulty of access of the substrate to the active sites of the enzyme. The immobilized enzyme did not show any changes in the optimal pH and temperature when compared to the free enzyme in both methods tested.

A β-galactosidase (E.C 3.2.1.23) é uma das enzimas mais empregadas na indústria de alimentos sendo utilizada na hidrólise da lactose. Neste trabalho foram utilizadas duas metodologias para imobilização desta enzima. Na primeira delas foi empregado como suporte um material híbrido à base de sílica que possui um grupo orgânico catiônico covalentemente ligado. A adsorção da enzima a este material apresentou eficiência que variou de 74 a 53% com o aumento da quantidade de enzima aplicada ao suporte. A baixa estabilidade térmica da enzima imobilizada obtida e as prováveis fracas interações envolvidas na sua adsorção a este suporte podem explicar o decréscimo de atividade observada durante as sucessivas bateladas de hidrólise da lactose. Na primeira batelada o grau de hidrólise foi de 90,9% e no final da última batelada (4ª), a enzima foi capaz de converter apenas 13% do substrato. A segunda metodologia utilizada foi imobilização covalente da enzima em um filme de celulose/líquido iônico modificado com uma poliamina e ativado com glutaraldeído. A presença da poliamina foi confirmada por análises de infravermelho. Após a imobilização, a enzima reteve 60% de sua atividade inicial. Bons resultados de hidrólise da lactose em batelada foram obtidos tanto a 7ºC como a 35ºC e foi possível reutilizar a enzima imobilizada por 16 ciclos consecutivos, a 7ºC, sem mudanças significativas na atividade enzimática. O valor de Km para a enzima imobilizada no material híbrido à base de sílica foi de 9,17 mM e para a enzima imobilizada nos filmes de celulose foi de 11,22 mM, ambos apresentaram um acréscimo quando comparados ao Km enzima livre (1,25 mM), devido à dificuldade de acesso do substrato ao sítio ativo da enzima. Não houve mudança no pH e temperatura ótimos da enzima imobilizada em relação à enzima livre em nenhum dos métodos testados. / β-galactosidase (E.C 3.2.1.23) is the most widely used enzymes in the food industry and its employed in the lactose hydrolysis process. In this study, two methodologies were used to test their immobilization. In the first, the enzyme was immobilized by adsorption in one silica based hybrid material that contains a cationic organic group covalently linked. The efficiency of immobilization showed a decrease of 74 to 53% by increasing the protein load applied to the support. The low thermo stability of the immobilized enzyme and the probable weak interactions involved in their adsorption, could explain the decrease in enzyme activity observed in the successive batch hydrolysis of lactose. In the first run, the degree of lactose hydrolysis was 90.9% and, at the end of the last run (4th), the enzyme was able to convert only 13% of the substrate. The second methodology used was the covalent immobilization of the enzyme on a cellulose/ionic liquid film, modified with a polyamine and activated using glutaraldehyde. The presence of a polyamine was confirmed by infrared analysis. After immobilization, the enzyme retained 60% of its initial activity. Highly efficient lactose conversion was achieved in a batch process at 7ºC and 35ºC and was possible to reuse the immobilized enzyme in 16 repeated cycles, at 7ºC, without any drastic decrease in enzyme activity. Km value for the immobilized enzyme in silica based hybrid material was 9.17 mM and for the enzyme immobilized in the film of cellulose/ionic liquid was 11.22 mM, both showing an increase compared with the Km value for free enzyme (1.25 mM), due to the difficulty of access of the substrate to the active sites of the enzyme. The immobilized enzyme did not show any changes in the optimal pH and temperature when compared to the free enzyme in both methods tested.

by Chan Sau Han. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.ii / ACKNOWLEDGMENT --- p.iii / CONTENTS --- p.iv / ABBREVIATIONS --- p.vi / Chapter CHAPTER 1 --- General Introduction / Chapter 1-A. --- Role of Copper in Biology --- p.1 / Chapter 1-B. --- A Brief Review on Radical Copper Proteins --- p.4 / Chapter 1-C. --- Objectives of This Work --- p.12 / Chapter 1-D. --- References --- p.13 / Chapter CHAPTER 2 --- Copper(II) and Zinc(II) Complexes containing N3O Tetradentate Ligands / Chapter 2-A. --- Introduction Results and Discussion --- p.14 / Chapter 2-B. --- Preparation of Tetradentate Ligands and Complexes --- p.27 / Chapter 2-C. --- Characterization --- p.36 / Chapter 2-D. --- Generation of Metal Phenoxyl Radical Species --- p.51 / Chapter 2-E. --- Summary --- p.57 / Chapter 2-F. --- References --- p.59 / Chapter CHAPTER 3 --- Copper(I) Complexes with N30 Tetradentate Ligands / Chapter 3-A. --- Introduction Results and Discussion --- p.62 / Chapter 3-B. --- Preparation of Copper(I) Complexes with N30 Tetradentate Ligands --- p.75 / Chapter 3-C. --- Characterization --- p.79 / Chapter 3-D. --- Reactivities of 86，87 and 88 toward Dioxygen --- p.88 / Chapter 3-E. --- Summary --- p.93 / Chapter 3-F. --- References --- p.94 / Chapter CHAPTER 4 --- Experimental Sections / Chapter 4-A. --- General Preparations and Physical Measurements --- p.97 / Chapter 4-B. --- Compounds Described in Chapter2 --- p.99 / Chapter 4-C. --- Compounds Described in Chapter3 --- p.113 / Chapter 4-D. --- Oxo-Transfer to Triphenylphosphine as Described in Chapter3 --- p.117 / Chapter 4-E. --- References --- p.119 / Chapter APPENDIX A --- 1H and13 C̐ưث1H ̐ưحNMR Spectra / Chapter A-1. --- Compounds Described in Chapter2 --- p.120 / Chapter A-2. --- Compounds Described in Chapter3 --- p.127 / Chapter APPENDIX B --- Crystallographic Data / Chapter B-1. --- X-ray Crystal Structure Data for Complexes in Chapter2 --- p.131 / Chapter B-2. --- X-ray Crystal Structure Data for Complexes in Chapter3 --- p.133 / Chapter APPENDIX C --- GC-MS Spectra / Chapter C-1. --- GC-MS Spectra for Standard Samples --- p.134 / Chapter C-2. --- GC-MS Spectra for the Reactions with Triphenylphosphine Described in Chapter3 --- p.136

M.S. / Biochemistry / The EPR spectrum of the Tyr-Cys· free radical in oxidized apoGAOX has been investigated, using a combination of approaches. Power saturation analysis has been used to resolve two unique spectra through Evolving Factor Analysis (EFA) global fitting, indicating the presence of two distinct free radical species in the sample. The component that dominates at low microwave power arises from the Tyr-Cys· side chain, while the high power component has not yet been assigned. The experimental results show that the EPR spectrum collected at low power includes approximately 7% of the high power component. EPR spectra have been collected for ten different isotope derivatives of GAOX, including ²H-labeled, ¹³C-labeled, 17[superscript]O-labeled, and ³³S-labeled forms. XSophe simulation of the EPR spectra has been performed for the isotopically labeled samples in order to determine the spectroscopic parameters - g-values, hyperfine coupling constants, and linewidths. The g-values and the methylene proton hyperfine coupling constants obtained for the isotopically labeled samples are consistent with the literature values. The magnitude of the hyperfine coupling constants associated with each of the nuclei confirms that significant electron spin density is found on the methylene protons, the alternating carbon atoms within the aromatic π system and the 2p[subscript]z orbital of both sulfur and oxygen. Moreover, the rotation angle of the methylene protons to the phenoxyl ring around the C1-C7 bond has been evaluated based on the experimentally defined hyperfine coupling constants of the two methylene protons.