Steady state fluorescence spectroscopy of the photosystem II core complex

Spectroscopic properties within the core complex of photosystem II were investigated by studying the influence of the wavelength of excitation on the fluorescence emission spectrum. At two temperatures, when the core complex of PSII isolated from spinach was excited at six different excitation wavelengths ranging from 436 nm to 520 nm, there is no difference in the maxima of the emission spectra of the core complex, and when the core complex was excited at 480, 489, 495 and 507 nm respectively, fluorescence intensities of maxima decrease with increasing of the absorbance of the beta-carotene molecules at the four excitation wavelengths. The extent of change of the shoulder of the spectra beyond 700 nm depends on the kind of pigment molecule excited. The excitation wavelength can influence the way of energy transfer in the core complex of photosystem II. By Gaussian deconvolution analysis, at least seven groups of chlorophyll a molecules were discovered. They are Chl a(660), Chl a(670), Chl a(680), Chl a(682), Chl a(684), Chl a(687) and Chl a(690).