Electronic and vibrational coherence in photosynthetic cofactors: Comparison of solutions and proteins

The interaction between photosynthetic cofactors and the surrounding bath o r protein environment is addressed via experimental measurements of the opt ical 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 stren gths vary between solutions and protein. In particular, the protein environ ment yields faster dephasing, faster spectral diffusion, and significantly more inhomogeneity than solutions.