FDMR of Chlorophyll triplets in Integrated Particles and Isolated Reaction Centers of Photosystem II. Identification of P680 Triplet.

Fluorescence detected magnetic resonance (FDMR) of various chlorophyll a triplets in PS II large particles was studied with the aim of identifying the nature of the different components underlying the complex line shape of the signals. The latter are deconvoluted into sums of Gaussians in different experimental conditions, and the charge recombination triplet is unequivocally identified as the source of two lines with negative signs at 722.5 and 992 MHz (\D\ = 0.0286 cm(-1), \E\ = 0.0043 cm(-1)). The origin of the other triplet signals from the integrated particles is discussed in terms of functional antenna components and products from alteration of the native environment of pigments. FDMR signals also arise from isolated reaction centre complexes and are all to be attributed to different triplet populations of the primary electron donor P680. The results are compared with those obtained by other authors on ADMR. The heterogeneity of P680 pigments in D1D2-cyt-b(559) complexes is shown to arise during preparation procedures.