Ma Ka Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 99-118). / Abstracts in English and Chinese. / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- What are prebiotics? --- p.1 / Chapter 1.2 --- Current prebiotics and their development --- p.2-3 / Chapter 1.3 --- The intestinal microflora --- p.3-4 / Chapter 1.3.1 --- Bacteroides --- p.5 / Chapter 1.3.2 --- Bifidobacteria --- p.5 / Chapter 1.3.3 --- Clostridia --- p.5-6 / Chapter 1.3.4 --- Lactobacilli --- p.6 / Chapter 1.4 --- Bacterial colonic fermentation --- p.7-8 / Chapter 1.4.1 --- Carbohydrates metabolism in colonic bacteria --- p.8-10 / Chapter 1.4.1.1 --- Carbohydrates metabolism in Bacteroides --- p.11 / Chapter 1.4.1.2 --- Carbohydrates metabolism in Bifidobacteria --- p.11 / Chapter 1.4.1.3 --- Carbohydrates metabolism in Clostridia --- p.11 / Chapter 1.4.1.4 --- Carbohydrates metabolism in Lactobacilli --- p.12 / Chapter 1.5 --- Health benefits of prebiotics --- p.12-13 / Chapter 1.6 --- Metabolites of fermentation: Short-chain fatty acids (SCFAs) --- p.14-15 / Chapter 1.7 --- Applications of prebiotics as functional food ingredients --- p.16 / Chapter 1.8 --- Methodology for evaluating prebiotics --- p.17 / Chapter 1.8.1 --- In vivo fermentation study --- p.17 / Chapter 1.8.2 --- Human clinical study --- p.17-18 / Chapter 1.8.3 --- In vitro fermentation study --- p.18-19 / Chapter 1.9 --- Methods of bacterial enumeration --- p.19-20 / Chapter 1.9.1 --- Fluorescent in situ hybridisation --- p.20-22 / Chapter 1.9.2 --- Bacterial enumeration by automatic image analysis --- p.22-23 / Chapter 1.10 --- Sugar alcohols --- p.23 / Chapter 1.10.1 --- Sugar alcohols and their functions --- p.23-25 / Chapter 1.10.2 --- Digestion and absorption of sugar alcohols --- p.25-26 / Chapter 1.10.3 --- Metabolism of sugar alcohols in humans --- p.26 / Chapter 1.10.4 --- Adverse effect of sugar alcohols --- p.26-27 / Chapter 1.11 --- Fermentation of sugar alcohols in colonic bacteria --- p.27 / Chapter 1.12 --- Project objectives --- p.28 / Chapter Chapter 2. --- Materials and Methods --- p.29 / Chapter 2.1 --- Materials --- p.29 / Chapter 2.2 --- Static batch culture fermentation --- p.29 / Chapter 2.2.1 --- Substrate preparation --- p.29-30 / Chapter 2.2.2 --- Human fecal inoculum preparation --- p.30-31 / Chapter 2.3 --- Dry matter and organic matter disappearance in batch fermentation --- p.31 / Chapter 2.4 --- Determination of flow rate in the continuous fermentation system. --- p.32-33 / Chapter 2.5 --- Three-stage continuous fermentation culture system --- p.34 / Chapter 2.5.1 --- Initial set-up --- p.34-35 / Chapter 2.5.2 --- Continuous fermentation --- p.35-36 / Chapter 2.6 --- Validation of fluorescent in situ hybridisation (FISH) method --- p.36 / Chapter 2.6.1 --- Oligonucleotide probes for FISH --- p.36-37 / Chapter 2.6.2 --- Cultivation of pure human intestinal bacterial culture --- p.37-38 / Chapter 2.6.3 --- Validation of oligonucleotide probes for FISH --- p.38-40 / Chapter 2.7 --- Bacterial enumeration of fermentation broth by FISH --- p.41 / Chapter 2.7.1 --- Automated image analysis --- p.41-42 / Chapter 2.7.2 --- Quantification of bacteria --- p.43 / Chapter 2.8 --- Gas chromatographic determination of short-chain fatty acids (SCFAs) --- p.44-46 / Chapter 2.9 --- Statistical analysis --- p.46 / Chapter Chapter 3: --- Results and Discussion --- p.47 / Chapter 3.1 --- Dry matter and organic matter disappearance in batch fermentations --- p.47-48 / Chapter 3.2 --- Validation of genus-specific oligonucleotide probes for FISH by pure bacterial culture --- p.48-50 / Chapter 3.3 --- FISH and multi-color FISH of human fecal bacteria --- p.50-53 / Chapter 3.4 --- Enumeration of fecal bacteria with the CellC software --- p.53-54 / Chapter 3.5 --- Colonic bacterial profile in batch culture in vitro fermentation --- p.55 / Chapter 3.5.1 --- Total colonic bacteria --- p.55-56 / Chapter 3.5.2 --- Bacteroides --- p.57-59 / Chapter 3.5.3 --- Bifidobacteria --- p.60-62 / Chapter 3.5.4 --- Clostridia --- p.63-64 / Chapter 3.5.5 --- Lactobacilli --- p.65-66 / Chapter 3.6 --- Short-chain fatty acids (SCFAs) in batch in vitro fermentation --- p.67 / Chapter 3.6.1 --- Total SCFAconcentration --- p.67-68 / Chapter 3.6.2 --- Acetate --- p.68 / Chapter 3.6.3 --- Propionate --- p.69 / Chapter 3.6.4 --- Butyrate --- p.69-70 / Chapter 3.7 --- Determination of flow rate in three-stage continuous fermentation system --- p.71-73 / Chapter 3.8 --- Colonic bacterial profile in three-stage continuous fermentation system --- p.74 / Chapter 3.8.1 --- Total colonic bacteria --- p.74-75 / Chapter 3.8.2 --- Bacteroides --- p.76 / Chapter 3.8.3 --- Bifidobacteria --- p.77-78 / Chapter 3.8.4 --- Clostridia --- p.79-80 / Chapter 3.8.5 --- Lactobacilli --- p.81 / Chapter 3.9 --- SCFAs in three-stage continuous fermentation system --- p.82 / Chapter 3.9.1 --- Total SCFA concentration --- p.82-87 / Chapter 3.9.2 --- SCFA molar ratio --- p.88-89 / Chapter 3.9.3 --- Acetate --- p.90-91 / Chapter 3.9.4 --- Propionate --- p.92-93 / Chapter 3.9.5 --- Butyrate --- p.94-95 / Chapter Chapter. 4 --- Conclusions and Future Works --- p.96-98 / List of References --- p.99-117 / Related Publications --- p.118

Le CO2 est une source de carbone propre pour les réactions chimiques, nombreux chercheurs ont étudié l'utilisation du CO2. Les alcools supérieurs sont des additifs de carburant propres. La synthèse des alcools supérieurs à partir de l'hydrogénation du CO a également été étudiée par de nombreux chercheurs, mais il existe peu de littératures sur la synthèse des alcools supérieurs à partir de l'hydrogénation du CO2, qui est une réaction complexe et difficile. Les catalyseurs utilisés pour la synthèse des alcools supérieurs nécessitent au moins deux phases actives et une bonne synergie. Dans notre étude, nous avons étudié les catalyseurs spinelle basés sur Co. Cu. Fe et l'effet des supports (CNTs et TUD-1) et celui des promoteurs (K, Na, Cs) à la réaction de HAS. Nous avons trouvé que le catalyseur CuFe-précurseur-800 est favorable pour la synthèse d'hydrocarbures en C2+ et d'alcools supérieurs. Dans l'hydrogénation du CO2, Co agit comme catalyseur de méthanisation plutôt que comme catalyseur FT, en raison du mécanisme de réaction différent entre l'hydrogénation du CO et celle du CO2. Afin d'inhiber la formation d'hydrocarbures de quantités importante, il est préférable de choisir des catalyseurs sans Co dans la réaction d'hydrogénation du CO2. En comparant les fonctions des CNT et du TUD-1, nous avons constaté que le CNT est un support parfait pour la synthèse de produits à longue chaîne (alcools supérieurs et hydrocarbures C2+). Le support TUD-1 est plus adapté à la synthèse de produits à un seul carbone (méthane et méthanol) .L'addition d'alcalis en tant que promoteurs conduit non seulement à augmenter la conversion de CO2 et H2, mais augmente également la sélectivité des produits visés fortement, des alcools supérieurs. Le catalyseur 0.5K30CuFeCNTs possède une productivités les plus élevées (370.7 g ∙ kg-1 ∙ h-1) d'alcools supérieurs à 350 ° C et 50 bar. / CO2 is a clean carbon source for the chemical reactions, many researchers have studied the utilization of CO2. Higher alcohols are clean fuel additives. The synthesis of higher alcohols from CO hydrogenation has also been studied by many researchers, but there are few literatures about the synthesis of higher alcohols from CO2 hydrogenation, which is a complex and difficult reaction. The catalysts that used for higher alcohols synthesis need at least two active phases and goodcooperation. In our study, we tested the Co. Cu. Fe spinel-based catalysts and the effect of supports (CNTs and TUD-1) and promoters (K, Na, Cs) to the HAS reaction. We found that catalyst CuFe-precursor-800 is beneficial for the synthesis of C2+ hydrocarbons and higher alcohols. In the CO2 hydrogenation, Co acts as a methanation catalyst rather than acting as a FT catalyst, because of the different reaction mechanism between CO hydrogenation and CO2 hydrogenation. In order to inhibit the formation of huge amount of hydrocarbons, it is better to choose catalysts without Co in the CO2 hydrogenation reaction. Compared the functions of CNTs and TUD-1, we found that CNTs is a perfect support for the synthesis of long-chain products (higher alcohols and C2+ hydrocarbons). The TUD-1 support are more suitable for synthesis of single-carbon products (methane and methanol).The addition of alkalis as promoters does not only lead to increase the conversion of CO2 and H2, but also sharply increased the selectivity to the desired products, higher alcohols. The catalyst 0.5K30CuFeCNTs owns the highest productivities (370.7 g∙kg-1∙h-1) of higher alcohols at 350 °C and 50 bar.

O uso das preparações alcoólicas ainda suscita questionamentos e influencia na segurança do cuidado em saúde. Os aspectos relacionados à aceitação e tolerância destes produtos são determinantes para melhoria da prática de higiene das mãos (HM). Diante do exposto, objetivou-se avaliar a utilização de duas preparações alcoólicas na HM segundo a Estratégia Multimodal da Organização Mundial da Saúde (OMS). Trata-se de um estudo com delineamento cross-over, randomizado, duplo-cego, realizado com profissionais de enfermagem por meio de entrevistas e avaliações objetivas das condições das mãos. Utilizaram-se duas preparações alcoólicas distintas, sendo uma formulação recomendada pela OMS (handrub) e a outra fornecida pela instituição em estudo (álcool gel). Nesse sentido, foi possível avaliar as características dos produtos que influenciam a sua aceitação e tolerância nas mãos dos profissionais. Na elaboração do banco de dados realizou-se dupla digitação e a análise no Statistical Package of Social Science (SPSS). Totalizou-se 42 profissionais de enfermagem, com predominância de mulheres (36; 85,7%), faixa etária entre 36 e 45 anos (14; 33,4%) e pertencentes à categoria de técnico e auxiliar de enfermagem (32; 76,2%). Quantos aos aspectos que influenciam a tolerância da pele, a maioria dos participantes referiu ter pele clara (16; 38,1%) ou morena clara (13; 31,0%), raramente fazer uso de cremes/loções para as mãos (11; 26,2%), bem como negaram o histórico de dermatites irritativas (30 - 71,4%), atópicas (37; 88,1%) e intolerância ao álcool (42; 100,0%). Outras dificuldades relativas ao uso das preparações alcoólicas e os aspectos da prática de HM dos profissionais, antes e após a participação no estudo também foram avaliados. A preparação alcoólica na apresentação handrub não apresentou aceitabilidade positiva para apenas uma das características avaliadas (ressecamento), enquanto para o álcool gel não houve aceitabilidade para duas características (textura e velocidade de secagem). Observou-se tolerância positiva para todas as características avaliadas na utilização do handrub, entretanto observou-se uma piora no aspecto escamosidade após a utilização do álcool gel. Embora questões relativas ao treinamento e supervisão não foram exploradas estas se mostram fundamentais quando os aspectos inerentes à qualidade das preparações antissépticas foram superadas. / The use of alcoholic preparations still raises questions and influences the safety of health care. Aspects related to the acceptance and tolerance to these products are crucial to improving the practice of hand hygiene (HH). This study aimed to evaluate the use of two alcoholic preparations in HH according to the World Health Organization (WHO) Multimodal Strategy. This cross-over, randomized and double- blind study was carried out with nursing professionals through interviews and objective assessments of the conditions of the hands. Two different alcoholic preparations were used, one formulation recommended by the WHO (handrub) and the other provided by the institution under study (alcohol gel). It was possible to evaluate the characteristics of the products that influence their acceptance and tolerance in the hands of professionals. For the development of the database, double entry and analysis using the Statistical Package of Social Science (SPSS) were carried out. In total, 42 nursing professionals participated, with a predominance of women (36; 85.7%), aged 36 to 45 years (14; 33.4%) and belonging to the category of technical and auxiliary nurses (32; 76.2%). Regarding the aspects that influence the tolerance of the skin, most participants reported having light skin (16; 38.1%) or light brunette skin (13; 31.0%), rarely using creams/lotions for the hands (11; 26.2%), and denied having a history of irritant (30; 71.4%) or atopic (37; 88.1%) dermatitis and alcohol intolerance (42; 100.0%). Other difficulties related to the use of alcoholic preparations and the aspects of the practice of HH by the professionals, before and after participation in the study, were also evaluated. The alcoholic preparation as handrub did not present positive acceptability only for one of the evaluated characteristics (dryness), whereas for alcohol gel there was no acceptability for two characteristics (texture and drying rate). There was positive tolerance for all assessed characteristics in the use of Handrub, however, worsening in the squamous aspect of the skin was observed after the use of alcohol gel. Although issues related to training and supervision have not been addressed, they are key issues when features intrinsic to the quality of antiseptic preparations have been overcome.

A oxidação seletiva de alcoóis é importante para a síntese de intermediários e produtos químicos utilizados na fabricação de inúmeros materiais. O interesse em novos métodos catalíticos para a oxidação de moléculas orgânicas tem aumentado juntamente com a busca por processos ecossustentáveis. Neste trabalho foram estudadas diferentes estratégias de deposição de nanopartículas bimetálicas de ouro e paládio sobre um suporte magnético, constituído por nanopartículas de magnetita revestidas por sílica. Dois métodos de síntese de nanopartículas bimetálicas de ouro e paládio foram estudados: (I) a síntese de nanopartículas bimetálicas formadas por ligas de ouro e paládio, seguida pela deposição dessas nanopartículas pré-formadas sobre o suporte catalítico e (II) a síntese de nanopartículas bimetálicas do tipo core-shell, por meio da redução sucessiva de ouro e paládio sobre o suporte catalítico. A morfologia dos catalisadores foi determinada por diferentes técnicas de microscopia eletrônica. O desempenho catalítico das nanopartículas bimetálicas foi estudado na reação modelo de oxidação de álcool benzílico com oxigênio. Os catalisadores mostraram-se ativos e seletivos para benzaldeído sem a necessidade do uso de solvente ou base e, após separação magnética, foram usados em sucessivas reações com desempenho satisfatório / The selective oxidation of alcohols is important for the synthesis of intermediates and chemical products used for the production of many materials. The interest in new catalytic methods for the oxidation of organic molecules has increased along with the search for eco-sustainable processes. In this thesis we studied different deposition strategies of gold and palladium bimetallic nanoparticles on a magnetic support, comprised by silica coated magnetite nanoparticles. Two synthetic methods for the preparation of supported gold and palladium bimetallic nanoparticles were investigated: (I) the synthesis of gold and palladium bimetallic nanoparticles, followed by deposition of the preformed nanoparticles on the catalytic support and (II) the synthesis of core-shell bimetallic nanoparticles, through the sequential reduction of gold and palladium on the catalytic support. The catalysts\' morphology was investigated by electronic microscopy techniques. The catalytic behavior of the bimetallic nanoparticles was investigated in the model reaction of the oxidation of benzyl alcohol with oxygen. The catalysts were active and selective for benzaldehyde without the use of solvent and base and, after magnetic separation, were able to be reused in successive runs and showed a good performance.

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / O estudo quÃmico do basidiomiceto Lentinus strigellus foi realizado atravÃs da investigaÃÃo da produÃÃo de metabÃlitos secundÃrios em diferentes meios de culturas, alÃm da sua utilizaÃÃo em processos de biorreduÃÃo de compostos carbonÃlicos prÃquirais (cetona e -cetoÃster). A partir de L. strigellus cultivado em meio de peptona foi possÃvel isolar os benzopiranos 2,2-dimetil-6-metoxicroman-4-ona, 4-hidroxi-2,2-dimetil-6-metoxicromano e (3R,4S)-3,4-dihidroxi-2,2-dimetil-6-metoxicromano do meio lÃquido. Do micÃlio, foram isolados o alcalÃide indÃlico echinulina e a antraquinona fisciona, ambos inÃditos para o gÃnero Lentinus. Do microrganismo cultivado em Czapek, enriquecido com caldo de batata, foram isolados do meio lÃquido os mesmos benzopiranos produzidos em peptona, alÃm de (3S,4S)-3,4-dihidroxi-2,2-dimetil-6-metoxicromano. Quando Czapek foi utilizado como meio de cultivo, foram isoladas a panepoxidona e a isopanepoxidona. CÃlulas em crescimento de L. strigellus em meio de batata-dextrose foram investigadas, pela primeira vez, na biorreduÃÃo estereoseletiva da acetofenona e nove derivados aromÃticos, alÃm das cetonas alifÃticas ciclo-hexilmetilcetona, octan-2-ona, undecan-2-ona e do -cetoÃster 4-cloroacetoacetato de metila. A maioria das cetonas aromÃticas foi convertida ao respectivo Ãlcool de configuraÃÃo S, em excessos enantiomÃricos superiores a 99%. Exceto para a undecan-2-ona, as cetonas alifÃticas foram reduzidas enzimaticamente ao Ãlcool de configuraÃÃo S em elevadas taxas de conversÃo e excessos enantiomÃricos. O -cetoÃster 4- cloroacetoacetato de metila foi quimiosseletivamente reduzido ao Ãlcool correspondente de configuraÃÃo R, mas com excesso enantiomÃrico moderado. / The chemical study of the basidiomicete Lentinus strigellus was done by the investigation of its secondary metabolites production in varied culture media, besides its utilization in the bioreduction of prochiral carbonyl compounds (ketone and - ketoester). From the liquid medium of L. strigellus grown in peptone broth, it was isolated the benzopyranes 2,2-dimethyl-6-methoxycroman-4-one, 4-hydroxy-2,2-dimethyl-6-methoxycromane and (3R,4S)-3,4-dihydroxy-2,2-dimethyl-6-methoxycromane . From the mycelium, the indol alkaloid echinuline and the antraquinone fiscione were isolated, both compounds reported for the first time in Lentinus. The same benzopyranes isolated from L. strigellus grown in peptone, besides (3S,4S)-3,4-dihydroxy-2,2-dimethyl-6-methoxycromane were isolated from the liquid medium of the microorganism grown in Czapek medium enriched with potato broth. When only Czapek was used as culture medium, panepoxidone and isopanepoxidone were isolated. Growing cells of L. strigellus in potato-dextrose medium were investigated, for the first time, in the stereoselective reduction of acetophenone and nine aromatic derivatives, besides the aliphatic ketones cyclohexylmethylketone, octan-2-one and undecan-2-one, and the -ketoester methyl 4-chloroacetoacetate. Most of the aromatic ketones were converted into the respective alcohols with S configuration in high enantiomeric excesses (> 99%). Except for undecan-2-one, the aliphatic ketones were enzimatically reduced to the alcohols with S configurations in high conversion ratios and enantiomeric excesses. -ketoester methyl 4-chloroacetoacetate was chemoselectivelly reduced to its corresponding alcohol with R configuration but with moderate ee.

Os marcadores orgânicos moleculares (hidrocarbonetos alifáticos, esteróis e álcoois) em amostras de sedimentos superficiais e de testemunhos curtos coletados em diápiros e pockmarks localizados no talude sul do Brasil, foram utilizados para identificar as possíveis contribuições biogênicas (autóctones / alóctones). De modo geral, tanto nas amostras superficiais como ao longo dos testemunhos, o maior acúmulo de carbono orgânico total nos pockmarks foi observado, indicando o possível aprisionamento de sedimentos e de matéria orgânica no interior das concavidades. A presença de β-sitosterol, campesterol, álcoois e n-alcanos pesados, indicaram contribuições terrígenas para a área de estudo, que pode ser advinda da descarga continental do Rio da Prata, uma vez que a predominância terrígena é proveniente das pradarias, típica vegetação do Uruguai e do sul do Rio Grande do Sul. O transporte de sedimentos terrígenos ocorre em direção ao norte, ao longo da plataforma continental sul brasileira, pela Corrente Costeira do Brasil. A presença de detritos de fitoplâncton e zooplâncton também ocorre devido à influência dos nutrientes do Rio da Prata. As possíveis liberações de gás/fluido, que sustentaram ecossistemas quimiossintéticos em diferentes intervalos de dois testemunhos em pockmark e diápiro foram constatadas através da presença relativamente maior de n-alcanos leves com número par de carbonos. / Organic molecular markers (aliphatic hydrocarbons, sterols and alcohols) in superficial and short cores sediment samples collected in diapirs and pockmarks located in the southern slope of Brazil were used in order to identify the possible biogenic contributions (autochthonous / allochthonous). In general, in surface samples and throughout the cores samples, the greatest accumulation of total organic carbon in the pockmarks was observed, indicating the possible entrapment of sediments and organic matter inside the concavities. The presence of β-sitosterol, campesterol, alcohols and heavy n-alkanes indicated terrigenous contributions to the study area, which may be due to the continental discharge of Río de la Plata, since the terrigenous predominance is due to the prairies, a typical vegetation of Uruguay and the south of Rio Grande do Sul. The terrigenous sediments transport is carried through the North, along the Brazilian continental shelf, by the Coastal Stream of Brazil. The presence of phytoplankton and zooplankton debris is also due to the influence of the nutrients contribution from Río de la Plata. Possible gas / fluid releases, which sustained chemosynthetic ecosystems at different intervals of two pockmark and diaper cores, were verified by the relative predominance of even-numbered carbon n-alkanes.

Enantiopure alcohols are valuable intermediates in fine organic synthesis, in particular for preparation of biologically active compounds. The necessity of preparing single enantiomer drugs in an optically pure form has triggered much research, especially in the pharmaceutical industry. The biocatalytical production of chiral alcohols by alcohol dehydrogenase enzymes is characterized by the asymmetric reduction of the corresponding ketones, usually with high degree of stereoselectivity. The commercial value of the enzymes as stereoselective biocatalysts has been a significant driving force in understanding features that control their mechanism of catalysis and stereoselectivity. This work focuses on two enantiocomplementary dehydrogenase enzymes ((R)- and 2-(S)-hydroxypropyl-CoM (HPC) dehydrogenases (DH)) of the epoxide carboxylation pathway in Xanthobacter autotrophicus strain Py2. The main goal of this dissertation is to kinetically, mechanistically and structurally characterize S-HPCDH and through the comparison studies with R-HPCDH reveal the basis for high degree of stereoselectivity exhibited by both enzymes. Analysis of the molecular structure of R-HPCDH and the homology model of S-HPCDH suggests a mechanism of substrate specificity in which the binding of the substrate sulfonate moiety at distinct sites on each stereoselective enzyme directs the orientation of the appropriate substrate enantiomer for the hydride abstraction. The positively charged residues responsible for binding the CoM moiety of the substrate were identified in R-HPCDH (Arg152 and Arg196), and in S-HPCDH (Arg211 and Lys214). Site-directed mutagenesis confirmed their importance in binding and orienting physiological substrates, but not the substrates lacking the CoM moiety. Extensive kinetic and mechanistic characterization of S-HPCDH reveals its key catalytic features similar to those of R-HPCDH, but also points out a few important differences. Furthermore, the role of the methionine residues flanking the substrate in the active site of both dehydrogenases was investigated. Substitution of these residues to alanine resulted in enzymes with significantly altered catalytic parameters and suggested their importance in binding and catalysis. Additionally, the X-ray crystal structures of the Met187Ala and Met192Ala mutants of R-HPCDH have revealed their role as "gate keepers," protecting the active site from the surrounding solvent. Kinetic analysis of Met187Leu and Met192Leu mutants implied a structural, rather than catalytic function of the methionines. It is proposed that steric clashes of the terminal methyl group of the HPC substrates with the nicotinamide ring of NAD+ are a major determinant of the enantioselectivity in S-HPCDH. This research provides the first side-by-side characterization of a pair of short-chain dehydrogenase/reductase (SDR) enzymes expressed simultaneously to act on two enantiomers of the same alcohol produced in a metabolic pathway. The R-HPCDH and S-HPCDH enzymes are distinguished from all other known members of the SDR family in using the novel sulfonate functional group of coenzyme M as a handle for chiral discrimination. These results provide a standard for examining the molecular basis of stereoselectivity in other such enzyme pairs.

<p>Odor discrimination ability was tested in four female South African fur seals (<em>Arctocephalus pusillus pusillus</em>) using a food-rewarded two-choice instrumental conditioning paradigm. The seals’ ability to distinguish between members of homologous series of aliphatic ketones (2-butanone to 2-heptanone) and alcohols (1-butanol to 1-heptanol) was assessed. The results showed that three out of four seals successfully discriminated between all of their stimulus combinations in both classes of odorants. One seal succeeded to reach the discrimination criterion with all 2-ketones but failed with all 1-alcohols.</p><p>No significant correlation between odor discrimination performance and structural similarity of the odorants in terms of differences in carbon chain length was found in either of the two chemical classes. Furthermore, it was found that the 2-ketones were significantly better discriminated than the 1-alcohols. The fact that both classes of odorants are known to be present in the natural environment of seals provides a possible explanation as to why most of the seals were able to successfully discriminate between them. The results of the present study support the notion that the sense of smell may play an important role in behavioral contexts such as social communication, foraging and reproductive behavior of fur seals.</p>

The first part of this thesis describes a synthetic strategythat provides all eight possible isomers of a given vic-aminoalcohol starting from vinylepoxides. The value of a generalroute is evident, as several isomers are needed ininvestigations of structure-activity relationships forpharmacologically active derivatives, and for optimizing theperformance of chiral ligands containing the amino alcoholmoiety. Vinylepoxides, obtained in high enantiomeric excess, werering-opened both with inversion and retention ofstereochemistry, delivering two diastereomeric amino alcoholswith high regio- and stereoselectivity. Via ring-closure toaziridines and subsequent regioselective ring-opening withsuitable oxygen nucleophiles, the two remaining amino alcoholswere selectively achieved. Within this study, two efficient protocols for theregioselective and stereospecific aminolysis of vinylepoxideshave been presented. Comparedto previous methods, theseprocedures use milder reaction conditions, shorter reactiontimes, generally give higher yields and are applicable to alarger set of substrates. Furthermore, the ring-closure ofvic-amino alcohols to the corresponding N-H vinylaziridines hasbeen investigated. Three routes have been found useful, whichone is preferred depends on substrate and scale. In the second part of the thesis, the synthetic strategy isapplied on the synthesis of Sphingosine and its regio- andstereoisomers. Moreover, a rapid way of determining relativeconfiguration of vic-amino alcohols is described, which shouldbe of substantial use when amino alcohols are formed bydiastereoselective reactions. amino alcohols, vinylepoxides, vinylaziridines, oxazolines,oxazolidinones, ring-opening, regioselective,diastereoselective, sphingosine, configuration, NMRspectroscopy.

Odor discrimination ability was tested in four female South African fur seals (Arctocephalus pusillus pusillus) using a food-rewarded two-choice instrumental conditioning paradigm. The seals’ ability to distinguish between members of homologous series of aliphatic ketones (2-butanone to 2-heptanone) and alcohols (1-butanol to 1-heptanol) was assessed. The results showed that three out of four seals successfully discriminated between all of their stimulus combinations in both classes of odorants. One seal succeeded to reach the discrimination criterion with all 2-ketones but failed with all 1-alcohols. No significant correlation between odor discrimination performance and structural similarity of the odorants in terms of differences in carbon chain length was found in either of the two chemical classes. Furthermore, it was found that the 2-ketones were significantly better discriminated than the 1-alcohols. The fact that both classes of odorants are known to be present in the natural environment of seals provides a possible explanation as to why most of the seals were able to successfully discriminate between them. The results of the present study support the notion that the sense of smell may play an important role in behavioral contexts such as social communication, foraging and reproductive behavior of fur seals.