Summary of optimization methods

Although the native protein can be used in the branched-photocycle architecture, it is ineffective and improvements are necessary. The quantum efficiency of the O —> P photoconversion ( 2 x 10" ) is low, and the O state has a low yield ( 1 to 3% under ambient conditions). Mutations directed at optimizing these two photophysical properties suggest that significant improvements can be made to enhance conversion into the branched photocycle intermediates. Site-directed mutants were created that enhance the yield of the O state and the quantum efficiency of the O —> P photoreaction. However, site-directed mutants are restricted to knowledge of the protein based on modeling information. Because there are many aspects of the photocycle yet to be discovered, more randomized mutagenesis methods are necessary to complete the optimization process. A summary of optimization methods is shown in Table 135.2. 

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