Abstract

Using time correlated single photon counting, we have studied electron transfer rates, k_ET in the homologous blue-copper proteins, azurins, obtained from Pseudomonas aeruginosa (Pae) and Alcaligenes faecalis (Afe). The salient difference between these proteins lies in the position of their single tryptophan residues. The tryptophan in azurin Pae, W48, is buried in the hydrophobic core of the protein while the tryptophan in azurin Afe, W118, lies on the protein surface, exposed to the solvent [1]. k_ET for the reaction W* + Az-Cu (II)→W^*+·+Az-Cu(I) was determined to be 1 × 10¹⁰ s⁻¹ and 0.5 × 10¹⁰s⁻¹ for Pae and Afe, respectively ; i.e. k_ET(W48)/k_ET(W118) = 2.

© 1986 Optical Society of America