The interaction of anionic surfactant sodium dodecyl sulfate (SDS) with photosystem II (PS II) was studied by ultraviolet (UV)absorption, fluorescence and Fourier transform infrared (FT-IR) spectroscopy. It was found that PS II was characteristics of tyrosyl residue fluorescence. The results have shown that there exist excitation energy transfers from the component at 232 nm in PS II proteins to the tyrosyl residues, and from these two amino acid residues to chlorophyll a. The effect of SDS on PS II caused the changes in these energy transfers, and also given rise to the changes in structural aspects of PS II protein skeleton and tyrosyl residues, which was dependent on the aggregate state of SDS molecules in solution. Below its critical micelle concentration (cmc), SDS effect facilitated the energy transfer from the component at 232 nm to the tyrosyl residues in PS II proteins, and also resulted in less micropolarity for tyrosyl residues, whilst at or above its cmc, SDS had an opposite effect. However, SDS exhibited an inhibition of the energy transfer from tyrosine residues to chlorophyll a, regardless of SDS concentration.

Key words: SDS, TYROSINE, ENERGY TRANSFER, IR