Electrophoretic Studies of Silk

A micro-electrophoretic technique was used to determine the characteristic pH-mobility curves for fibroin and for sericin and to ascertain the extent of removal of the latter during degumming by the soap and enzyme processes. The data suggest that sericin contains a much greater proportion of reactive groups than fibroin, and indicate the importance of obtaining either uniform or complete removal of sericin during degumming processes. The isoelectric points are shown to vary slightly with ionic strength. In acetate buffers of 0.02 M ionic strength, the isoelectric point of fibroin is 3.6 and that of sericin, 4.3. Large ions of complex structure such as phthalate or picrate appear to have specific effects which are readily detectable by the electrophoretic technique. Dissolved fibroin adsorbed on glass particles and fibroin regenerated from similar solutions had the same isoelectric points but different pH-mobility curves. Fibroin regenerated after dissolving in solutions of lithium bromide gave the same pH-mobility curve as untreated fibroin.