FTIR Difference Spectroscopy for the Study of Photosystem I A$_{1 }$Acceper

ORAL

Abstract

Photosystem I (PS I) is a protein complex which carries out light-induced charge separation in oxygenic photosynthesis. Phylloquinone acts as the secondary electron acceptor in PS I. The A$_{1}$accepter is of interest because it has the lowest reduction potential of any quinone found in nature. In \textit{Men}B mutant PS I particles from \textit{Synechocystis} sp. 6803, a plastoquinone-9 molecule occupies the A$_{1}$ binding site instead of phylloquinone. Using \textit{men}B PS I particles, it has been shown that it is possible to replace plastoquinone-9 in the A$_{1}$ site with phylloquinone. To probe the molecular properties of phylloquinone and its environment in both the neutral and reduced state, we have used time-resolved step-scan FTIR difference spectroscopy (TRSS FTIR DS) to supply dynamic structural information concerning the electron-transfer cofactor. We have produced time-resolved A$_{1}^{-}$/A$_{1}$ FTIR DS using \textit{men}B mutant PS I particles in which phylloquinone has been reintroduced into the A$_{1}$ binding site. We also have obtained time-resolved A$_{1}^{-}$/A$_{1}$ FTIR difference spectra for \textit{men}B PS I particles that are globally $^{13}$C labeled where $^{12}$C labeled phylloquinone was incorporated into the A$_{1}$ binding site. By incorporating $^{12}$C labeled phylloquinone into $^{13}$C labeled PS I, we are able to identify carbonyl (C=O)-sensitive bands of A$_{1}^{-}$ and A$_{1}$.

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Authors

  • Nan Zhao

  • Milind Purohit

    Univ of South Carolina, Benedict College, Sc 29204, Univ. South Carolina, Benedict College, Univ South Carolina, GA Tech, Central Microscopy Research Facility, University of Iowa, Iowa City, Iowa 52242, USA, Department of Chemistry, University of Sri Jayewardenepura, Nugegoda, Sri Lanka, Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303, USA, Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, Department of Physics, University of Alabama at Birmingham, Birmingham, AL 35294, College of William \& Mary, Harvard University, Benedict College, SC 29204, Massachusetts Institute of Technology, University of Applied Science, Bielefeld, Germany, Francis Marion University, Physics Dept., Emory University, Emory University, Formerly Emory University, currently UCLA, Physics Department, Georgia State University, Univ. of Georgia, Dept. of Chemistry, Universidad Nacional de Quilmes, Argentina, Pr, Dr, Derpartment of Physics, Florida A\&M University, Tallahassee, FL-32307, Department of Physics, Emory University, Georgia Institute of Technology, Naval Research Laboratory, University of Alabama, Tsinghua University, Lawrence Berkeley National Laboratory, Vanderbilt University, Jagellonian Univ., Univ. of Bonn, North Carolina A\&T State Univ., North Carolina Central Univ., Duke Univ. and TUNL, Georgia State University, Dept of Physics, Emory University, Cell Biology Department, Emory University, Physics Department, Emory University, University of South Carolina