Microheterogeneity of rat alpha-fetoprotein

A purified and homogeneous preparation of rat alpha-fetoprotein (AFP) was separated into two components, AFPa and AFPb, by polyacrylamide gel electrophoresis. These two components had a definite difference in electrostatic net charge and gave only a single band on sodium dodecyl sulfate-electrophoresis. Neuraminidase-treated AFP gave clearly separable, slower moving four to six and finally two components depending on the time of incubation with neuraminidase. The time-dependent conversion of each AFPa and AFPb into slower migrating components upon neuraminidase treatment was confirmed by re-electrophoresis of separated and similarly treated AFPa and AFPb.