Abstract
Solid-state NMR spectra of natural abundance 13C in reaction centers from photosynthetic bacteria Rhodobacter sphaeroides R-26 was measured. When the quinone acceptors were removed and continuous visible illumination of the sample was provided, exceptionally strong nuclear spin polarization was observed in NMR lines with chemical shifts resembling those of the aromatic carbons in bacteriochlorophyll and bacteriopheophytin. The observation of spin polarized 15N nuclei in bacteriochlorophyll and bacteriopheophytin was previously demonstrated with nonspecifically 15N-labeled reaction centers. Both the carbon and the nitrogen NMR studies indicate that the polarization is developed on species that carry unpaired electrons in the early electron transfer steps, including the bacteriochlorophyll dimer donor P860 and probably the bacteriopheophytin acceptor. I. Both enhanced-absorptive and emissive polarization were seen in the carbon spectrum; most lines were absorptive but the methine carbons of the porphyrin ring (alpha, beta, gamma, ) exhibited emissive polarization. The change in the sign of the hyperfine coupling at these sites indicates the existence of nodes in the spin density distribution on the tetrapyrrole cofactors flanking each methine carbon bridge.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Allen J. P., Feher G., Yeates T. O., Komiya H., Rees D. C. Structure of the reaction center from Rhodobacter sphaeroides R-26: the cofactors. Proc Natl Acad Sci U S A. 1987 Aug;84(16):5730–5734. doi: 10.1073/pnas.84.16.5730. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Feher G., Hoff A. J., Isaacson R. A., Ackerson L. C. ENDOR experiments on chlorophyll and bacteriochlorophyll in vitro and in the photosynthetic unit. Ann N Y Acad Sci. 1975 Apr 15;244:239–259. doi: 10.1111/j.1749-6632.1975.tb41534.x. [DOI] [PubMed] [Google Scholar]
- Goldstein R. A., Boxer S. G. Effects of nuclear spin polarization on reaction dynamics in photosynthetic bacterial reaction centers. Biophys J. 1987 Jun;51(6):937–946. doi: 10.1016/S0006-3495(87)83421-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McDermott A. E., Creuzet F., Gebhard R., van der Hoef K., Levitt M. H., Herzfeld J., Lugtenburg J., Griffin R. G. Determination of internuclear distances and the orientation of functional groups by solid-state NMR: rotational resonance study of the conformation of retinal in bacteriorhodopsin. Biochemistry. 1994 May 24;33(20):6129–6136. doi: 10.1021/bi00186a012. [DOI] [PubMed] [Google Scholar]
- Oh-Hama T., Seto H., Miyachi S. 13C nuclear magnetic resonance studies on bacteriochlorophyll a biosynthesis in Rhodopseudomonas spheroides S. Arch Biochem Biophys. 1985 Feb 15;237(1):72–79. doi: 10.1016/0003-9861(85)90255-3. [DOI] [PubMed] [Google Scholar]
- Okamura M. Y., Isaacson R. A., Feher G. Primary acceptor in bacterial photosynthesis: obligatory role of ubiquinone in photoactive reaction centers of Rhodopseudomonas spheroides. Proc Natl Acad Sci U S A. 1975 Sep;72(9):3491–3495. doi: 10.1073/pnas.72.9.3491. [DOI] [PMC free article] [PubMed] [Google Scholar]
- de Groot H. J., Gebhard R., van der Hoef I., Hoff A. J., Lugtenburg J., Violette C. A., Frank H. A. 13C magic angle spinning NMR evidence for a 15,15'-cis configuration of the spheroidene in the Rhodobacter sphaeroides photosynthetic reaction center. Biochemistry. 1992 Dec 15;31(49):12446–12450. doi: 10.1021/bi00164a021. [DOI] [PubMed] [Google Scholar]