1) Glucocorticoid receptor components I, II and III were characterized physically and biologically, and tested for their artifactual generation during electrofocusing. Intracellularly, activation was shown to coincide with a stepwise increase of pI from I to III. The distinctive pIs of the receptor components were shown not to be due to carrier ampholyte binding. 2) Human growth hormone (hGH) produced by genetically modified bacteria was isolated by a single step of moving boundary electrophoresis, followed by electrophoretic extraction from the gel. The method rests on the finding that at pH 7.6, hGH is selectively retarded. It is then collected by initiating a second moving boundary ("restacking"). 3) Photoaffinity-labeled glucagon receptor was isolated by SDS-PAGE, followed by electrophoretic extraction and concentration. Isolation yield was 0.01% relative to the starting material of purified membranes; purity was 60%. The product was near-homogeneous by the criterion of silver stained SDS-PAGE patterns at 2 protein load levels. The isolation demonstrates the applicability to SDS-PAGE of the previously described preparative method based on gel slice extraction.