Conception of hystons in bacterial photosynthesis: spectra, exciton dynamics, and electron transfer

Abstract

It has been shown that among the great diversity of available vibrational modes there are two types so called h μ - and h α - hyston modes in the light-harvesting (LH) antennas and in the complexes of the reaction centers (RCs), which produce high modulated broadening of excitonic spectra with radically different temperature behavior. At the same time the h μ - and h α -modes initiate different activationless electron transfer (ET) processes in the RCs. Novel formulas is presented, which making it possible to describe known experimental data on the half-width of the B800, B850 absorption for LH2 antennas and the P870 and P960 absorption for RCs as well as on the temperature effect on the ET rate. The primary ET is considered as a resonant nonradiative transition between P* and P + B A - states with next stabilization (P is a special pair, B A is an accessory bacteriochlorophyll in A-branch of RC). It has been shown that the h α -mode with own frequency in the range of 130-150 cm -1 controls the primary ET from P* to bacteriopheophytin (H A ).The ET matrix elements are of 12.7 ± 0.9 and 12.0 ± 1.2 cm -1 for Rps. viridis and Rb. sphaeroides respectively. An oscillation mechanism is discussed for ET from P* to B A and then to H A . It is assumed that water fulfils the transmission function in the primary ET. It is obtained that the h μ -mode of 304 cm -1 governs the secondary ET from H A to ubiquinone in Rb. sphaeroides RC.