Wavelength-dependent photocycle activity of xanthorhodopsin in the visible region

Abstract

Xanthorhodopsin (xR) is a dual-chromophore proton-pump photosynthetic protein comprising one retinal Schiff base and one light-harvesting antenna salinixanthin (SX). The excitation wavelength-dependent transient population of the intermediate M demonstrates that the excitation of the retinal at 570nm leads to the highest photocycle activity and the excitations of SX at 460 and 430nm reduce the activity to ca. 37% relatively, suggesting an energy transfer pathway from the S2 state of the SX to the S1 state of the retinal and a quick internal vibrational relaxation in the S2 state of SX prior to the energy transfer from SX to retinal.