A New Method for Determination of Alpha-1-antitrypsin Phenotypes Using Isoelectric Focusing on Polyacrylamide Gel Slabs

Abstract

Phenotyping methods for alpha-1-antitrypsin were developed utilizing isoelectric focusing on 1 mm. acrylamide gel slabs. Alpha-1-antitrypsin proteins have isoelectric points in the pH region from 4.2 to 4.65. Utilizing ampholines with a pH range of 3.5–5 or 3–6, the proteinase inhibitor (Pi) phenotypes containing the more common M, A, S, F alleles were found to be readily identifiable and may be studied both qualitatively and quantitatively by this method. Protein distributions of the various Pi allele products as illustrated by densitometric traces show patterns similar to those found in the conventional two-dimensional acid starch gel—crossing antigen-antibody electrophoresis. The high resolving ability of isoelectric focusing indicated the presence of M allele-like products in FZ, SS, and ZZ Pi types. The total procedure time was reduced from VA days to 4 hours. The potential resolving power of this method appears sufficient to identify also the untested remaining alleles.