Pulsed proton-deuterium 1,2H ENDOR and 2H-2H TRIPLE resonance of H-bonds and cysteinyl .beta.-CH2 of the D. gigas hydrogenase [3Fe-4S]+ cluster

This paper presents the results of 2 H Mims and 1 H Davies pulsed ENDOR of the [3Fe-4S] + cluster of Desulfovibrio gigas hydrogenase. It also describes the first 2 H Mims pulsed TRIPLE-resonance experiments, on the exchangeable deuterons. The 1 H ENDOR data show that the intrinsic isotropic hyperfine couplings for the β-CH 2 protons of the three cysteines bound to iron fall in the range 1.3≤a≤1.9 MHz. These values, which often had been estimated at a=1 MHz, will allow better interpretation of solution NMR data for paramagnetic [nFe-mS] clusters