Amino acid radicals are central to long-range electron transfer (ET) in biological processes; for instance, DNA synthesis and repair enzymes utilize tyrosine and tryptophan in the ET chains. In the blue copper protein, azurin, tryptophan and tyrosine radicals have been observed. Here, we discuss quantum yields for tryptophan fluorescence as well as formation of the neutral tryptophan radical in several azurin mutants.  We focus on Cu- and Zn-substituted azurin, tryptophan isotopologues, and various external inorganic electron acceptors.  These results elucidate the mechanisms of excited-state ET reactions of the buried tryptophan residue in azurin.

Tryptophan radical in azurin:  Effects of deuteration and metal substitution on quantum yields of fluorescence and radical formation

251st National Meeting (2016)

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