This title appears in the Scientific Report :
2012
Please use the identifier:
http://hdl.handle.net/2128/4905 in citations.
Einfluss unkonventioneller Medien auf die Selektivität ThDP-abhängiger Enzyme
Einfluss unkonventioneller Medien auf die Selektivität ThDP-abhängiger Enzyme
This work constitutes the first comprehensive study on the influence of organic solvents and ionic liquids on the selectivity of thiamine diphosphate (ThDP)- dependent enzymes. The focus of this work was the analysis of chemo- and stereoselectivity in the presence of various additives under comparab...
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Personal Name(s): | Gerhards, Tina (Corresponding author) |
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Contributing Institute: |
Biotechnologie; IBG-1 |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2012
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Physical Description: |
XIV, 199 S. |
Dissertation Note: |
Heinrich-Heine-Universität Düsseldorf, Diss., 2012 |
ISBN: |
978-3-89336-846-4 |
Document Type: |
Dissertation / PhD Thesis |
Research Program: |
ohne Topic |
Series Title: |
Schriften des Forschungszentrums Jülich. Schlüsseltechnologien / Key Technologies
54 |
Subject (ZB): | |
Link: |
OpenAccess |
Publikationsportal JuSER |
This work constitutes the first comprehensive study on the influence of organic solvents and ionic liquids on the selectivity of thiamine diphosphate (ThDP)- dependent enzymes. The focus of this work was the analysis of chemo- and stereoselectivity in the presence of various additives under comparable experimental conditions. In this context the influence of 13 organic solvents and 14 ionic liquids in various concentrations on six different ThDP-dependent enzymes was examined. Almost 900 biotransformations were performed to analyze the mixed carboligation of benzaldehyde and acetaldehyde. Here, theoretically four different products (acetoin, PAC, HPP and benzoin) are formed, each in both enantiomeric forms. From changes in the chemo- and stereoselectivity conclusions can be drawn concerning the molecular interaction of organic solvents and ionic liquids. The results are summarized below: $\textit{Influence of organic solvents on the chemoselectivity}$ The analysis of the results shows, that the influence of organic solvents on ThDP-dependent enzymes follows two general trends. The more pronounced the chemoselectivity of an enzyme in buffer, meaning the more exclusively a product is formed in comparison to the other three possible products of the carboligation, the more robust this reaction is against influences due to organic solvent addition (Figure 39B). Moreover, in many cases a shift in the chemoselectivity of the enzymes was observed in the direction of the smaller product. This happens at the expense of the synthesis of the larger product in the presence of organic solvents (Figure 39B). However, these two major trends are influenced by other, less dominant effects. $\textit{Influence of organic solvents on the stereoselectivity}$ The overall consideration of the effects of organic solvents on the stereoselectivity of ThDP-dependent enzymes also followed two trends (IV.4.1): An enzyme that catalyzes the formation of a product with excellent ee (> 99 %) in buffer cannot be influenced concerning its stereoselectivity for this product by organic cosolvents (Figure 44). This is probably due to the relatively high energy of stabilization of the acceptor aldehyde directly before carboligation. Reactions with lower [...] |