Effects of Conformation and Environment on Bacteriochlorophyll Optical Spectra: Correlations of Calculated Spectra with Structural Results.

摘要

Recent structural data for (bacterio) chlorophylls and chlorins as isolated molecules and in proteins have demonstrated the skeletal distortions of the chromophores that can be imposed by crystal packing and/or protein constraints. We consider here the possibility that such conformational variations can affect the highest occupied and lowest unoccupied molecular orbital levels of the chromophores and thereby modulate their light-absorption properties. We apply the concept to the bacteriochlorophyll (BCHL) (und a) - protein antenna complex from Prosthecochloris aestuarii, whose structure has been solved by x-ray diffraction and which exhibits a series of low energy absorption maxima at low temperatures that range from 793-825 nm(sup 3). 8 refs., 1 fig., 1 tab.