Enhanced light harvesting and photocurrent generation activities of biohybrid light–harvesting 1–reaction center core complexes (LH1-RCs) from Rhodopseudomonas palustris

Abstract

A light harvesting system that effectively drives photocatalytic component is essential for converting solar light into chemical energy. Here we addressed the extension of light harvesting activity and presented a quantitative analysis of the functional linkage between light harvesting and a photocatalytic reaction of biohybrid light-harvesting 1–reaction center core complex (LH1-RC from Rhodopseudomonas palustris). Light harvesting wavelengths were extended by a series of fluorophores (Alexa647, 680, 750, and ATTO647N), which were covalently attached to LH1-RC (LH1-RC-Fluors). Femtosecond transient absorption spectroscopy revealed ultrafast excitation energy transfer (EET) from the fluorophores to bacteriochlorophyll a pigments in LH1 (B875), followed by charge separation in RC. The rate of EET increased with increase in the spectral overlap between the emission bands of the fluorophores and the absorption band of B875. The attachment of the external light harvesting fluorophores boosted the maximum yield of charge separation and photocurrent generation activity. We discussed the effects of the number of fluorophores attached to LH1-RC and location of the fluorophores in a lipid bilayer environment on light harvesting activity.