lipid content in the PSII-DGDG complex as the total infrared absorbance of DGDG in the 1650-1500 cm -~ region is practically zero (cf. Fig. 1). 2.4. Chemicals.
J o u r n a l of
MOLECULAR STRUCTURE ELSEVIER
Journal of Molecular Structure 444 (1998) 123-133
Protein structure of photosystem II studied by FT-IR spectroscopy. Effect of digalactosyldiacylglycerol on the tyrosine side chain residues I.S. Gabashvili, A. Menikh, J. S6gui, M. Fragata* D~partement de Chimie et Biologie, Section de Chimie et Groupe de recherche en ~nergie et information biomol~culaires (GREIB), Universitd du Quebec ~ Trois-Rivibres, Trois-Rivikres, Quebec, Canada G9A 5H7
Received 4 August 1997; accepted 10 September 1997
Abstract Digalactosyldiacylglycerol (DGDG), a non-ionic galactolipid of the thylakoid membrane, enhances the activity of the oxygen-evolving complex in photosystem II (PSII). To elucidate the structural aspects of the DGDG effect, a Fourier transform infrared (FT-IR) spectroscopic study of PSII and the P S I I - D G D G complex was performed in the 1650-1500 cm -~ region. Analysis of the [ P S I I - D G D G ] - PSII difference spectrum indicates that DGDG induces significant changes in the intensities and positions of the tyrosine bands in the PSII spectra. The es intensity in the 1630-1580 cm -~ region of tyrosine increases concomitantly with a loss in u 19aintensity from 1520 to 1500 cm
