Two-dimensional 67Zn HYSCORE spectroscopy reveals that a Zn-bacteriochlorophyll aP' dimer is the primary donor (P840) in the type-1 reaction centers of Chloracidobacterium thermophilum.

摘要: Chloracidobacterium (C.) thermophilum is a microaerophilic, chlorophototrophic species in the phylum Acidobacteria that uses homodimeric type-1 reaction centers (RC) to convert light energy into chemical using (bacterio)chlorophyll ((B)Chl) cofactors. Pigment analyses show these RCs contain BChl aP, Chl aPD, and Zn2+-BChl aP′ approximate ratio 7.1 : 5.4 : 1. However, functional roles of three different are not yet fully understood. It was recently demonstrated aPD primary electron acceptor. Because Zn2+-(B)Chl present at low abundance, it suggested donor might be dimer molecules. In this study, we utilize isotopic enrichment high-resolution two-dimensional (2D) 14N 67Zn hyperfine sublevel correlation (HYSCORE) spectroscopy demonstrate cation, P840+, C. RC indeed dimer. Density theory (DFT) calculations measured electron-nuclear parameters P840+ indicate spin density on distributed nearly symmetrically over two molecules as expected RC. To our knowledge only example photochemical which metallated differently than those antenna.