Abstract
Molecular weights of bovine .alpha.s3- and .alpha.s4-casein [in milk] were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Analysis by least squares of natural logarithm of molecular weight vs. distance of migration gave a MW of 27,800 .+-. 900 daltons for each protein. The value agrees closely with the MW (26,000 daltons) for bovine .alpha.s3-casein reported by Richardson and Creamer and is less than 31,800 daltons for reduced .alpha.s5-casein reported by Toma and Nakai.