Long-range electron transfer (ET) is central to biological processes, including photosynthesis, cellular respiration, and enzymatic catalysis. Amino acid radicals are common intermediates that enable multi-step electron transfer reactions; for instance, DNA synthesis and repair enzymes utilize tyrosine and tryptophan in the ET chains. We have focused on a blue copper protein, azurin, as a model system for amino acid radicals because this protein has been shown to stabilize tryptophan radicals in various positions. In particular, a buried tryptophan neutral radical at position 48 has been shown to persist for several hours.  Here, we present results on Trp48 isotopologues in azurin.  The resonance Raman and quantum yield data elucidate the effect of deuteration on the vibrational structure and quantum yield for formation of the neutral Trp48 radical.  These data will be discussed in the context of proton-coupled ET reactions for tryptophan.

Effects of deuteration on the formation and vibrational structure of a neutral tryptophan W48 radical in azurin

251st National Meeting (2016)

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