MEASUREMENT OF THE G-TENSOR OF THE P700+CENTER-DOT SIGNAL FROM DEUTERATED CYANOBACTERIAL PHOTOSYSTEM-I PARTICLES

We report high-field continuous wave EPR spectra of P700+. in preparations obtained from deuterated cyanobacteria (Synechococcus lividus). Measurements were performed with photosystem I (PS-I) preparations, whole cells from cyanobacteria grown in (H2O)-H-2, and photosystem II (PS-H) preparations, as well as with protonated PS-I preparations. Because of the significantly improved resolution of our 140-GHz spectrometer (as compared with X- or Q-band EPR) the principal values of the g-tensor of the primary donor P700+. could be resolved and measured with high accuracy as g11 = 2.00304, g22 = 2.00262, and g33 = 2.00232. Other signals arising from Mn2+ and a dark signal from PS-IL at g almost-equal-to 2.00266 are distinguished from the P700+. g-tensor powder pattern. The measured g values are compared with those of several bacterial reaction center donors.