Isoelectric focusing of myelin membrane proteins

Human myelin was isolated from the white matter of autopsy brains. Myelin proteins were characterized by isoelectric focusing in ultrathin slab gels in a pH range from 3.5 to 10 after solubilization with urea and Nonidet P 40. The protein profile in the acidic region (pH below 6.2) revealed at least twelve faint bands which comprised only a few percent of the total myelin proteins. Most of the myelin proteins were focused in the neutral range (pH 6.2-7.8) which showed two sharper and three broader major bands, the total number of bands in this region being about twenty. The basic pH range (pH above 7.8) contained about 30% of the proteins, and revealed a very intense band near the cathode with seven to nine weaker bands below pH 9.0. When the myelin was partially delipidated prior to solubilization, an additional broad "band" was observed at the area pH 8.0-8.5.