Variability in electrophoretic mobility of Gi-like proteins: effect of SDS

Two forms of Gi-like protein are resolved in both somatic cells and mouse gametes when Sigma SDS (95% grade) is used during polyacrylamide gel electrophoresis, whereas only a single species is resolved when Bio-Rad SDS (electrophoresis grade) is used. These two Gi-like proteins are likely to reflect two distinct species, since (i) the two species resolved in the presence of Sigma SDS migrate with the same electrophoretic mobility upon re-electrophoresis in the presence of Sigma SDS and (ii) exchanging Sigma SDS for Bio-Rad SDS resolves a single species, whereas exchanging Bio-Rad SDS for Sigma SDS resolves two species.