Electronic Excited States of the CP29 Antenna Complex of Green Plants: A Model Based on Exciton Calculations

We have suggested a model for the electronic excited states of the minorplant antenna, CP29, by incorporating a considerable part of the currentinformation offered by structure determination, site-directed mutagenesis,and spectroscopy in the modeling.We have assumed that the electronic excited states of the complex havebeen decided by the chlorophyll-chlorophyll (Chl) and Chl-proteininteractions and have modeled the Coulombic interaction between a pairof Chls in the point-dipole approximation and the Chl-protein interactionsare treated as empirical fit parameters.We have suggested the Qy dipole moment orientations and the siteenergies for all the chlorophylls in the complex through a simultaneoussimulation of the absorption and linear dichroism spectra.The assignments proposed have been discussed to yield a satisfactoryreproduction of all prominent features of the absorption, linear and circulardichroism spectra as well as the key spectral and temporal characteristics ofthe energy transfer processes among the chlorophylls.The orientations and the spectral assignments obtained by relatively simpleexciton calculations have been necessary to provide a good point ofdeparture for more detailed treatments of structure-function relationship inCP29. Moreover, it has been discussed that the CP29 model suggested canguide the studies for a better understanding of the structure-functionrelationship in the major plant antenna, LHCII.