[Magnetic relaxation of water protons and the state of the water photodissociation system in chloroplasts].

The spin-spin relaxation time T2 of water protons is measured in chloroplast suspensions. It is shown that chloroplast lamellae efficiently increase the rate of proton magnetic relaxation, this effect being a linear function of chloroplast concentration. There is a fast exchange between the water molecules in different environments, thus the measured relaxation rate is a weight average of all water molecules. The rate of proton relaxation is decreased when membrane bound manganese is removed from chloroplasts by tris-washing procedure. The relaxation effect is slightly reduced in the presence of Photosystem II electron acceptors.