Enzyme selectivity efficiency

The first simple method using isotopic labelling has been developed to confirm the actual and observed selectivities in the enzymatic hydrolysis of unsymmetrical diacetates and to measure the enzyme selectivity efficiency. The simple method consists of enzymatic hydrolysis of the unsymmetrical diacetate followed by labelling of the hydroxyacetate formed with CD3CO2D-DCC and enzymatic rehydrolysis of the labelled compound under identical reaction conditions. The amount of label lost, as determined by H NMR spectroscopy, directly indicates the extent of regioselective action of the enzyme. For example, enzymic hydrolysis using pig liver acetone powder (FLAP) of the racemic glycerol diacetate (208) yielded a mixture (1 9) of the 1-hydroxy ester (209) and the 2-hydroxy ester (210). Isolation of the 2-hydroxy... 

The experimental evidences that medium engineering might represent an efficient method to modify or improve enzyme selectivity (alternative to protein engineering and to the time-consuming search for new catalysts) were immediately matched by the search for a sound rationale of this phenomenon. The different hypotheses formulated to try to rationalize the effects of the solvent on enzymatic enantioselectivity can be grouped into three different classes. The first hypothesis suggests that... 

Catalytic behaviour of the footprint materials followed Michaelis-Menten kinetics, yielding a Michaelis constant and catalytic rate constant A cat for each imprinted matrix. The value of characterises the interaction of the enzyme with the substrate, similar to but not equal to dissociation constants. The constant Acat is the rate at which the active site converts the substrate to product. Together, the ratio kcaJKm is the enzyme selectivity, which describes the active site s efficiency in catalysing a reaction on a particular substrate. 

The use of a-transglucosidases in the large-scale manufacture of novel bioderivatives is stiU limited by several factors such as enzyme selectivity, stability, and, in some cases, efficiency. To overcome these Umitations and further enlarge the appUcatimis of these enzymes, the latest protein engineering technologies have been used to tailor biocatalysts with specific properties for novel oligosaccharide. 

Fine tuning of enzyme formulations might increase the present number of industrially available enzymes from 350 to a few thousands biocatalysts. In particular, the development of new formulations that enhance selectivity, efficiency and stability is crucial. In addition, a closer collaboration between organic chemists and molecular biologists can lead to novel bio-inspired catalyst systems that combine the best of two worlds. 

The desire to mimic enzymatic systems has led to an active area of research involving synthetic porphyrin models of enzyme active sites, especially for monooxygenase enzymes of the cytochrome P-450 ". An analysis of comparative studies dealing with the selectivity, efficiency and stability for both synthetic porphyrin models and natural systems has shown that efficiency arises from the control of the environment of the enzyme active site. Thus, in a first approach, the design of synthetic supramolecular architecture for porphyrin models... 

Using enzyme principles, efficient and selective synthetic catalysts can be designed that may be more practical than enzymes in the industrial section, due to their more robust entities and greater tolerance to reaction conditions such as temperature and pH. 

As can be seen in Table II the responses within a group of related compounds differ. This may be due to differences in enzyme selectivity but also in how efficiently the (di)phenols are oxidized/reduced at the electrode surface, especially in the case of the CDH biosensor where the applied potential is rather close to the formal potential of several of the diphenols. The differences are probably also caused by differences in the stability of the products formed in the electrochemical reduction/oxidation and/or enzymatic reduction. Another possible explanation is the formation of by-products that cannot be recycled between the enzyme and the electrode. 

The objective of the present work was to demonstrate efficient routes to sugar-based vinyl monomers based on enzyme selectivity, determine whether 6-O -acryl glucoside was polymerizable and to synthesize water-soluble acrylic acid-based copolymers that also contain vinyl-sugar repeat units. 

The catalysts based on ruthenium undoubtedly have priority in the TH reactions of ketones due to their excellent, sometimes approaching enzyme-like, efficiencies, selectivities, and their rich chemistry which allows the introduction of diverse types of chiral ligands. However, the possibility of using other platinum-group metal catalysts have been demonstrated as a valid alternative to ruthenium systems. Since the first reports of Ir-based ATH of ketones, for example by Graziani and coworkers in 1982 [87], interest in iridium catalysts, which have often been successfully used in TH of olefins, has been growing [88]. 

Enzymes form products from substrates with high selectivity and efficiency at ambient temperatures. Enzymes feature well-defined binding pockets that bind substrates during reactions using non-covalent interactions. The behavior is analogous to a lock and key systan in which the substrate (key) has a complementary size and shape to the binding site (lock). Enzymes selectively promote the formation of the transition state and intermediates of a particular reaction. 

As previously reported by other workers (Frentzen, etal., 1983), we find that the spinach enzyme quite efficiently selects 18 1-ACP in preference to 16 0-ACPfrom a mixture containing any of several combinations of the two. In agreement with Frentzen, etal. (1983), we also find that the pea enzyme is less selective for the unsaturated acyl substrate than is the spinach ATI. 

EFCs are very promising, when considering biocompatibility, selectivity, efficiency, and sensitivity criteria. In addition, EFCs could be employed to power nano-and microelectronic portable devices, dmg delivery systems, biosensors, and IMDs [2,4,7]. The high selectivity of enzymes makes their use as natural catalysts in fuel cell applications very beneficial by eliminating problems of cross-reactions and poisoning of the electrodes. This allows for membraneless single-compartment fuel... 

Biosensors ai e widely used to the detection of hazardous contaminants in foodstuffs, soil and fresh waters. Due to high sensitivity, simple design, low cost and real-time measurement mode biosensors ai e considered as an alternative to conventional analytical techniques, e.g. GC or HPLC. Although the sensitivity and selectivity of contaminant detection is mainly determined by a biological component, i.e. enzyme or antibodies, the biosensor performance can be efficiently controlled by the optimization of its assembly and working conditions. In this report, the prospects to the improvement of pesticide detection with cholinesterase sensors based on modified screen-printed electrodes are summarized. The following opportunities for the controlled improvement of analytical characteristics of anticholinesterase pesticides ai e discussed ... 

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