Other ee Assays

The infrared radiation caused by the heat of reaction of an enantioselective enzyme-catalyzed transformation can be detected by modern photovoltaic infrared (IT)-thermographic cameras equipped with focal-plane array detectors. Specifically, in the lipase-catalyzed enantioselective acylation of racemic 1-phenylethanol (20), the (K)- and (S)-substrates were allowed to react separately in the wells of microtiter plates, the (7 )-alcohol showing hot spots in the IR-thermographic images (113,114). Thus, enantioselective enzymes can be identified in kinetic resolution. However, quantification has not been achieved thus far by this method, which means that only those mutants can be identified which have E values larger than 100 (113-115). 

Another method for assaying the activity and stereoselectivity of enzymes at in vitro concentrations is based on surface-enhanced resonance Raman scattering (SERRS) using silver nanoparticles (116). Turnover of a substrate leads to the release of a surface targeting dye, which is detected by SERRS. In a model study, lipase-catalyzed kinetic resolution of a dye-labeled chiral ester was investigated. It is currently unclear how precise the method is when identifying mutants which lead to E values higher than 10. The assay appears to be well suited as a pre-test for activity. 

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A number of other ee assays relying on the use of fluorescence have been described, although their general utility in the high-throughput evaluation of enantioselective enzymes remains to be demonstrated in most cases (66-70). A high-throughput ee... 

Other ee assays have been described, although in several cases the actual degree of throughput was not specified [10]. These systems include assays based on color tests [8,46 - 48,60], IR-thermography [49,61], circular dichroism [62], fluorescence [63], and even special forms of gas chromatography [64], Moreover, optically active compounds capable of enantioselective recognition of chiral substrates can be used as... 

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