Electron transfer processes in cytochromecytocrome oxidase system studied by laser induced optoacoustic spectroscopy

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

Congreso; 37th Meeting of the American Society for Photobiology; 2014

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 proteins due to charge transfer are studied by laser-induced photoacoustic measurements (LIOAS). The proteins studied are the CuA centres of cytochrome C oxidase subunit II [1] and the cytochrome c552. Deconvolution methods for signal analysis, in combination with an appropriate model were used for the determination of structural volume changes. Three different systems were analyzed: each protein separately and the mixing of the two proteins with their absorbances matched, in phosphate buffer solution. In each case, three well-separated processes were identified: a fast one (prompt) with a decay time 1 ≤ 10 ns; a slower process with a lifetime 2 ca. 200-400 ns; and a longest-lived component with a lifetime longer than 1 µs. The pre-exponential factors φi of the three components at several temperatures were plotted as E φi vs (cp/β). In all cases, good linear correlations were obtained. The slopes of the lines represent the structural volume change associated with each of the processes, in each case multiplied by the respective quantum yield of the process.