Electronic and Vibrational Coherence in Photosynthetic Cofactors: Comparison of Solutions and Proteins

Abstract

The interaction between photosynthetic cofactors and the surrounding bath or protein environment is addressed via experimental measurements of the optical coherence responses from bacteriochlorophyll_a (Bchl_a) chromophores within the photosynthetic reaction center (RC) of Rhodobacter sphaeroides and solutions of Bchl_a monomers in THF and pyridine. The results indicate that both the spectrum of fluctuations and chromophore bath coupling strengths vary between solutions and protein. In particular, the protein environment yields faster dephasing, faster spectral diffusion, and significantly more inhomogeneity than solutions.