Photochemically induced dynamic nuclear polarization (photo-CIDNP) has been observed in membrane fragments of heliobacterium Heliobacillus mobilis without further isolation by C-13 magic-angle... Show morePhotochemically induced dynamic nuclear polarization (photo-CIDNP) has been observed in membrane fragments of heliobacterium Heliobacillus mobilis without further isolation by C-13 magic-angle spinning (MAS) solid-state NMR under continuous illumination with white light. In the C-13 photo-CIDNP MAS NMR spectra of heliobacterial membrane fragments, two sets of signals are observed, allowing characterization, of the primary radical pair. One set, showing enhanced absorptive (positive) signals, arises from the BCh1 g donor, while the set of emissive (negative) signals is assigned to the 8(1)-hydroxy Ch1 a acceptor. Hence, under these sample conditions, both donor and acceptor sides are either monomeric or composed of identical cofactors. The occurrence of the differential relaxation (DR) mechanism suggests a donor triplet lifetime in the microsecond range. It appears that the occurrence of the solid-state photoCIDNP effect is a general feature of primary radical pairs in natural photosynthesis. Show less
