Abstract

Quantum calculations of the MRINDO /1/ type for the prosthetic groups of the reaction center Rps. viridis including outer atomic orbitals are presented. In Fig.l the electron density distribution of the lowest Rydberg type orbital is depicted. It concentrates on the two pyrrol rings I their methyl groups and those around the dimer. It extends also into the monomers B_L and b_m and weakly into the pheophytines H_L and H_M. There are asymmetries which favour the L-branch. In particular the electron density on the tyrosine M208 is larger than the one on phenylalanine L181. The transition from the HOMO of the dimer into this Rydberg orbital becomes a low excitation denoted P_R close to the well known P^* transition. It carries no oscillator strength couples only weakly to P* but has a strong permanent dipole of 20D pointing along the symmetry axis.

© 1992 The Author(s)