CONTRIBUTION TO THE DETERMINATION OF PROTEIN HYDROPHOBICITY .1. DETERMINATION OF THE HYDROPHOBICITY OF SELECTED CEREAL AND MILK-PROTEINS USING THEIR SODIUM DODECYL-SULFATE BINDING-CAPACITIES

The sodium dodecylsulphate (SDS) binding capacities of secalin, gliadin and gluten in the presence of a very low SDS concentration were determined and compared to the SDS binding capacities of bovine serum albumin (BSA), beta-lactoglobulin, ovalbumin und beta-casein. The SDS binding capacities of endosperm proteins determined in phosphate buffer (pH 6.0) are very low. Only 0.6-mu-g .. 0.8-mu-g SDS were bound to 500-mu-g of the proteins. This low SDS binding capacities do not correlate with the expected hydrophobicity of these proteins. In comparison, 500-mu-g of ovalbumin, beta-lactoglobulin and BSA each bind 0.5, 5.9 and 13.5-mu-g SDS, respectively. According to literature the SDS binding capacities of these proteins are in correlation with the surface hydrophobicity determined with cis-parinaric acid using the fluorescence probe method. The SDS binding capacities of endosperm proteins increased in the presence of 0.1 N acetic acid and consequently 6.2-mu-g .. 6.9-mu-g SDS were bound to 500-mu-g of the corresponding proteins. beta-casein described as a highly hydrophobic protein binds only 0.9-mu-g SDS to 500-mu-g of it in phosphate puffer (pH 6.0) and 1.2-mu-g SDS in 0.1 N acetic acid, respectively.