SOLUBILIZATION OF PHOTOSYNTHETIC PIGMENT-PROTEIN COMPLEXES

Abstract

Studies utilizing fractionation of photosynthetic pigment-protein complexes from the chloroplast thylakoid membrane often employ dodecylsulfate at a concentration of 10 mg mL−1 to disrupt membrane structure prior to electrophoretic fractionation of the complexes. We investigated the effect of varying dodecylsulfate concentration on the solution/air interfacial surface tension in the absence and presence of the same concentrations of thylakoid membranes used by four different fractionation systems that have been commonly employed to fractionate photosynthetic pigment-protein complexes. Concentrations of dodecylsulfate in the range5–10 mg mL−1, normally utilized to treat thylakoids prior to fractionation, were effective in reducing the interfacial surface tension to levels equivalent to control solutions without added thylakoid membranes. However, thylakoid membranes treated with these concentrations of dodecylsulfate are not resolved into discrete pigment-protein complexes when subjected to electrophoresis on an agarose gel, and do not produce significant amounts of pigment-containing complexes with a molecular size < 100 000 as measured by filtration with size-exclusion membranes. We conclude that many surfactant systems empirically developed to fractionate photosynthetic pigment-protein complexes may not fully solubilize the complexes prior to the electrophoretic step.