Alpha 1 antitrypsin M1: a new common genetically determined variant.

A new common variant (M1) of alpha 1 antitrypsin was detected by isoelectric focusing of serum in a pH gradient of 3.5-5.0 in polyacrylamide gels. The variant can be clearly distinguished from the common M type only when alpha 1 antitrypsin M is present in the same serum. It cannot be recognized on starch gel electrophoresis. The gene frequency in a population sample of United States whites was .09.