Photoacoustic studies of electron transfer processes in proteins

DAVID GARA, PEDRO M.; BILMES, GABRIEL; BRASLAVSKY, SILVIA

Cordoba

Encuentro; XI Encuentro Latinoamericano de Fotoquimica y Fotobiologia; 2012

The long-range (10 to 25 Å) charge transfer process in protein complexes is a fundamental process in respiratory and photosynthetic machinery. There are several open questions about the contributions of the environment in these long-range interactions as well as about the influence of the separation between the donor (D) and acceptor (A) partners. In this work the structural movements in modified proteins due to charge transfer are studied by laser-induced photoacoustic measurements. The systems are CuA centres of cytochrome C oxidase subunit II [1], and two mutants of cytochrome P450 (K97C and Q397C) with a Ru(II)(bpy)32+ complex, acting as electron donor upon excitation, attached at different positions to the protein [2,3]*. Deconvolution methods for signal analysis, in combination with an appropriate model are used for the determination of structural volume changes as a function of the distance between D and A. To analyse the enthalpy-entropy compensation effect and the possible correlation with the Marcus reorganization energy () for the charge recombination process, experiments are performed in buffers of various monovalent cations (Li+, Cs+ and N(CH3)4+).