title: Bacteriopheophytin a in the active branch of the reaction center of rhodobacter sphaeroides is not disturbed by the protein matrix as shown by 13C photo-CIDNP MAS NMR.
abstract: The electronic structure of bacteriopheophytin a (BPhe a), the primary electron acceptor (ΦA) in photosynthetic reaction centers (RCs) of the purple bacterium Rhodobacter sphaeroides, is investigated by photochemically induced dynamic nuclear polarization (photo-CIDNP) magic-angle spinning (MAS) NMR spectroscopy at atomic resolution. By using various isotope labeling systems, introduced by adding different (13)C selectively labeled δ-aminolevulinic acid precursors in the growing medium of R. sphaeroides wild type (WT), we were able to extract light-induced (13)C NMR signals originating from the primary electron acceptor. The assignments are backed by theoretical calculations. By comparison of these chemical shifts to those obtained from monomeric BPhe a in solution, it is demonstrated that ΦA in the active branch appears to be electronically close to free bacteriopheophytin. Hence, there is little effect of the protein surrounding on the cofactor functionally which contributes with its standard redox potential to the electron transfer process that is asymmetric.
authors: Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors: Karthick Babu
authors: KB
authors: Sai Sankar Gupta
authors: A
authors: A
authors: Alia
authors: Francesco
authors: F
authors: Buda
authors: Huub J M
authors: HJ
authors: de Groot
authors: Jörg
authors: J
authors: Matysik
mesh_terms: D000622:Aminolevulinic Acid / Q000737:chemistry; D002247:Carbon Isotopes / Q000737:chemistry; D007553:Isotope Labeling; D008027:Light; D019906:Nuclear Magnetic Resonance, Biomolecular; D010674:Pheophytins / Q000737:chemistry* / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D010674:Pheophytins; C006678:bacteriopheophytin; D000622:Aminolevulinic Acid