Photo-conversion of chlorophylls in higher-plant CP43 characterized by persistent spectral hole burning at 1.7 K

The chlorophyll–protein complex CP43 is a proximal-antenna subunit important for excitation energy transfer from peripheral light-harvesting antenna to the Photosystem II (PSII) reaction centre. We report persistent spectral hole burning at 1.7 K in the Qy(0,0) origin and Qy(1,0) vibrational satellite bands of chlorophyll a (chl a) in CP43 isolated from higher plants. The isolated CP43 is known to possess two quasi-degenerate ‘red’ trap states. We find persistent hole burning in the primary trap exhibits a photoconversion property, with a photoproduct located well outside its inhomogeneous distribution. This photoconversion of trap chl a molecules also occurs with non-selective white light illumination. The contribution of the ‘red’ states to CP43 absorption is discussed.