Identification of Fourier Transform Infrared Signals from the Non-Heme Iron in Photosystem II1

1 July 1995

journal article
research article
Published by Oxford University Press (OUP) in The Journal of Biochemistry

Vol. 118 (1) , 9-12
https://doi.org/10.1093/oxfordjournals.jbchem.a124897

Abstract

Fourier transfer infrared (FTIR) signals originating from a high-potential electron acceptor in PS II were studied by flash-induced FTIR difference spectroscopy. Redox titration of these signals using ferri-ferrocyanide mixtures showed midpoint potentials (_m of 489± 12 and 426±9 mV at pH 5.5 and 6.5, respectively, revealing a pH dependence of about-60 mV/pH unit. These E_m values and pH dependence were in good agreement with those of the non-heme iron, so-called Q₄₀₀, * located between Q^A and Q^B. This indicates that the observed FTIR signals are due to changes in ligands of the non-heme iron and surrounding protein moieties induced on photoreduction from Fe³ to Fe^2-.

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