The effect of dehydration and (2)H2O/H2O isotope substitution on electron transport reactions and relaxation of proton-containing groups was studied in chromatophore membranes of Ectothiorhodospira shaposhnikovii. During dehydration (including isotope substitution of hydrate water) of preliminarily dehydrated isolated photosynthetic membranes there was a partial correlation between hydration intervals within which activation of electron transport from high-potential cytochrome c to photoactive bacteriochlorophyll dimer P890 of photosynthetic reaction center and variation of spin-lattice and spin-spin proton relaxation time was observed. Partial correlation between hydration intervals can be considered as evidence of correlation between mobility of non-water proton-containing groups with proton relaxation frequency approximately 10(8) sec(-1) with efficiency of electron transfer at the donor side of the chain.