Effects of Energy Disorder on the Excitonic Structure of Cyclic Photosynthetic Antenna Complexes
Abstract
The light harvesting (LH) complexes of purple bacteria exhibit cyclic arrays of bacteriochlorophyll (BChl) molecules with the number of these molecules ranging between 9 and 32. Nearest neighbor BChl a-BChl a couplings are sufficiently strong to yield Frenkel exciton bandwidths of about 1300 cm-1. Since proteins carry glass-like structural heterogeneity, the effects of energy disorder (both diagonal and off-diagonal) on the excitonic levels need to be considered. A new approach for systematic analysis of this problem is discussed, one that is based on symmetry adapted basis defect (BDP) patterns. An arbitrary defect pattern can be written as a linear combination of BDP. This approach offers several advantages over brute-force methods especially when the energy disorder is weak, meaning that the disorder-induced couplings between exciton levels are comparable to a smaller than the level spacings. The utility of our symmetry based approach is illustrated for thr B850 ring of Rps. acidophila. Localization-extendedness patterns are shown and their implications for Stark spectroscopy discussed. >
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1998
- Bibcode:
- 1998APS..MAR.S1007W