This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Sivakumar, V. Articles by Hastings, G. Search for Related Content PubMed PubMed Citation Articles by Sivakumar, V. Articles by Hastings, G.

Photo-Oxidation of P740, the Primary Electron Donor in Photosystem I from Acaryochloris marina

Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303

Correspondence: Address reprint requests to Gary Hastings, Fax: 404-651-1427; E-mail: ghastings{at}gsu.edu.

Fourier transform infrared spectroscopy (FTIR) difference spectroscopy in combination with deuterium exchange experiments has been used to study the photo-oxidation of P740, the primary electron donor in photosystem I from Acaryochloris marina. Comparison of (P740⁺-P740) and (P700⁺-P700) FTIR difference spectra show that P700 and P740 share many structural similarities. However, there are several distinct differences also: 1), The (P740⁺-P740) FTIR difference spectrum is significantly altered upon proton exchange, considerably more so than the (P700⁺-P700) FTIR difference spectrum. The P740 binding pocket is therefore more accessible than the P700 binding pocket. 2), Broad, "dimer" absorption bands are observed for both P700⁺ and P740⁺. These bands differ significantly in substructure, however, suggesting differences in the electronic organization of P700⁺ and P740⁺. 3), Bands are observed at 2727(-) and 2715(-) cm^-1 in the (P740⁺-P740) FTIR difference spectrum, but are absent in the (P700⁺-P700) FTIR difference spectrum. These bands are due to formyl CH modes of chlorophyll d. Therefore, P740 consists of two chlorophyll d molecules. Deuterium-induced modification of the (P740⁺-P740) FTIR difference spectrum indicates that only the highest frequency 13³ ester carbonyl mode of P740 downshifts, indicating that this ester mode is weakly H-bonded. In contrast, the highest frequency ester carbonyl mode of P700 is free from H-bonding. Deuterium-induced changes in (P740⁺-P740) FTIR difference spectrum could also indicate that one of the chlorophyll d 3¹ carbonyls of P740 is hydrogen bonded.

This article has been cited by other articles:

				T. Tomo, Y. Kato, T. Suzuki, S. Akimoto, T. Okubo, T. Noguchi, K. Hasegawa, T. Tsuchiya, K. Tanaka, M. Fukuya, et al. Characterization of Highly Purified Photosystem I Complexes from the Chlorophyll d-dominated Cyanobacterium Acaryochloris marina MBIC 11017 J. Biol. Chem., June 27, 2008; 283(26): 18198 - 18209. [Abstract] [Full Text] [PDF]

				R. Wang, V. Sivakumar, T. W. Johnson, and G. Hastings FTIR Difference Spectroscopy in Combination with Isotope Labeling for Identification of the Carbonyl Modes of P700 and P700+ in Photosystem I Biophys. J., February 1, 2004; 86(2): 1061 - 1073. [Abstract] [Full Text] [PDF]