Photoinduced chlorophyll charge transfer state identified in the light-harvesting complex II from a marine green alga .

The light-harvesting complex II of (-LHCII), a green alga, differs from that of spinach (-LHCII) in chlorophyll (Chl) and carotenoid (Car) compositions. We investigated ultrafast excitation dynamics of -LHCII with visible-to-near infrared time-resolved absorption spectroscopy. Absolute fluorescence quantum yield ( ) of LHCII and spectroelectrochemical (SEC) spectra of Chl and were measured to assist the spectral analysis. Red-light excitation at Chl Q-band, but not Car-band, induced transient features resembling the characteristic SEC spectra of Chl and Chl , indicating ultrafast photogeneration of Chl-Chl charge transfer (CT) species; and Car declined whereas CT species increased upon prolonging excitation wavelength, showing positive correlation of Chl deactivation with Chl-Chl CT formation. Moreover, ultrafast Chl -to-Chl and Car-to-Chl singlet excitation transfer were illustrated. The red-light induction of Chl-Chl CT species, as also observed for -LHCII, is considered a general occurrence for LHCIIs in light-harvesting form.