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Volume 24, Issue 1-2, Pages 79-87

Rapid-scan FTIR difference spectroscopy applied to ubiquinone reduction in photosynthetic reaction centers: Role of redox mediators

Alberto Mezzetti1,2,3

1Service de Bioénergétique, Biologie Structurale et Mécanismes, IBiTec-S, CEA-Saclay, Gif-sur-Yvette, France
2LASIR UMR 8516, Université Lille 1, Villeneuve d'Ascq, France
3Service de Bioénergétique, Biologie Structurale et Mécanismes, IBiTec-S, Bât 532, CEA-Saclay, 91191 Gif-sur-Yvette cedex, France

Copyright © 2010 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Rapid-scan FTIR difference spectroscopy was used to investigate light-induced reduction of the ubiquinone QB, and the oxidation kinetics of QB and QH2 by external mediators in isolated reaction centers (RCs) from R. sphaeroides. As redox mediators, a Ferrocyanide/N,N,Nʹ,Nʹ-tetramethyl-p-phenylenediamine (TMPD) mixture and an Ascorbate/2,3,5,6-tetramethyl-p-phenylenediamine (DAD) mixture are compared.

Results show that TMPDred rapidly reduces the photoproduced P870+ primary donor. The process is fast enough to record rapid-scan FTIR spectra devoid of P870+ bands down to 260 K. Results show also that TMPDox oxidises both QB and QH2 faster than DADox. In particular, QB is oxidised faster than QH2 at all temperatures studied.

Results are discussed in the framework of time-resolved infrared studies on R. sphaeroides RCs, showing advantages/drawbacks of the proposed experimental approach.