Structures of functional sites in PS II studied by ENDOR and PELDOR

Abstract

The structures of the functional sites in photosystem II in higher plants have been studied by electron-nuclear double resonance (ENDOR), electron spin echo envelope modulation and pulsed electron-electron double resonance (PELDOR). On the acceptor side the distances from the primary acceptor quinone to P680 and triplet chlorophyll were determined on the basis of the dipolar interaction between the radical pair. On the donor side the microenvironment of tyrosine Z radical (Y2.) was studied by ENDOR to elucidate the specific electron transfer function. PELDOR of the Mn4 cluster in the S0 and S2 states and tyrosine D radical (YD.) revealed that spin projections on the four manganese atoms are necessary to estimate the distance between them.