Characterization of the Primary Radical Pair in Reaction Centers of Heliobacillus mobilis by 13C Photo-CIDNP MAS NMR

• Published in: Biochemistry (Easton) Vol. 47; no. 16; pp. 4629 - 4635
• Main Authors: Roy, Esha, Rohmer, Thierry, Gast, Peter, Jeschke, Gunnar, Alia, A, Matysik, Jörg
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 22.04.2008
• Subjects: Carbon Isotopes; Free Radicals - chemistry; Helicobacter - chemistry; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Photochemistry; Time Factors
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi800030g

Photochemically induced dynamic nuclear polarization (photo-CIDNP) has been observed in membrane fragments of heliobacterium Heliobacillus mobilis without further isolation by 13C magic-angle spinning (MAS) solid-state NMR under continuous illumination with white light. In the 13C 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 BChl g donor, while the set of emissive (negative) signals is assigned to the 81-hydroxy Chl 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 photo-CIDNP effect is a general feature of primary radical pairs in natural photosynthesis.