The FMO Complex in a Glycerol–Water Mixture

Experimental findings of long-lived
quantum coherence in the Fenna–Matthews–Olson
(FMO) complex and other photosynthetic complexes have led to theoretical
studies searching for an explanation of this unexpected phenomenon.
Extending in this regard our own earlier calculations, we performed
simulations of the FMO complex in a glycerol–water mixture
at 310 K as well as 77 K, matching the conditions of earlier 2D spectroscopic
experiments by Engel et al. The calculations, based on an improved
quantum procedure employed by us already, yielded spectral densities
of each individual pigment of FMO, in water and glycerol–water
solvents at ambient temperature that compare well to prior experimental
estimates. Due to the slow solvent dynamics at 77 K, the present results
strongly indicate the presence of static disorder, i.e., disorder
on a time scale beyond that relevant for the construction of spectral
densities.