Nitrogen ligation to manganese in the photosynthetic oxygen-evolving complex: continuous-wave and pulsed EPR studies of photosystem II particles containing nitrogen-14 or nitrogen-15

摘要: The possibility of nitrogen ligation to the Mn in oxygen-evolving complex from photosystem II was investigated with electron paramagnetic resonance (EPR) and spin echo envelope modulation (ESEEM) spectroscopies using {sup 14}N- 15}N-labeled preparations. Oxygen-evolving preparations were isolated a thermophilic cyanobacterium, Synechococcus sp., grown on medium containing either 14}NO{sub 3{sup {minus}}} or 15}NO{sup {minus}}{sub 3} as sole source nitrogen. substructure multiline EPR signal, which arises S{sub 2} state enzyme, measured continuous-wave EPR. No changes detected peak positions upon substitution 15}N for 14}N, indicating that this is not due superhyperfine coupling ligands. To detect potential ligands couplings lesser magnitude than could be observed conventional methods, spin-echo experiments also performed signal. Fourier transform light-minus-dark time domain ESEEM data shows at 4.8 MHz 14}N samples absent 15}N. This gives unambiguous evidence weak hyperfine complex. Possiblemore » origins interaction are discussed.« less