Static and dynamic disorder of the exciton system in light harvesting complexes LH2 of purple bacteria /
The role of conical intersection topography on the photoisomerization of retinal

Living systems exist at temperatures of about 300 K and as a result their molecular functions are subjected to significant disorder.  The thrive to understand how the mechanisms underlying biological functions can withstand this disorder, or even exploit it, poses a great challenge to both experiment and theory.  We describe in this lecture the role of disorder on the excitonic system of light harvesting complexes LH2.  The presentation is based on a combination of  molecular dynamics and quantum chemistry calculations of the protein and its chromophores that provided the input to a theoretical analysis.  This analysis is based on an elegant random matrix theory (static disorder), on a numerical calculation of exciton spectra and  line shapes (dynamic disorder), as well as on a polaron model that captures in the framework of an analytical theory succinctly  the effect of electron - phonon coupling on exciton spectra (+line shapes) and  coherence length.

I will briefly present recent results that describe the existence of conical intersections of qualititive distinct topographies in retinal and the effect of this difference on the molecule's photoisomerization.