[NMR paper] 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.

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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.

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.

J Phys Chem B. 2013 Mar 1;

Authors: Sai Sankar Gupta KB, Alia A, Buda F, de Groot HJ, Matysik J

Abstract
The electronic structure of bacteriopheophytin a (BPhe a), the primary electron acceptor (?A) in photosynthetic reaction centers (RCs) of the purple bacterium Rhodobacter (R.) sphaeroides, is investigated by photochemically induced dynamic nuclear polarization (photo-CIDNP) magic-angle spinning (MAS) NMR spectroscopy at atomic resolution. By using various isotope labelling systems, introduced by adding different 13C selectively labelled ?-aminolevulinic acid precursors in the growing medium of R. sphaeroides wild type (WT), we were able to extract light-induced 13C 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 ?A 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.


PMID: 23452037 [PubMed - as supplied by publisher]



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