Patent ID: 7074580

Claim:
In a process for obtaining a pharmaceutical product containing a mixture of polypeptides, each of which consists essentially of alanine, glutamic acid, tyrosine and lysine, wherein the mixture has an average molecular weight from 4000 to 13,000 Daltons and in the mixture the molar fraction of alanine is 0.427, of glutamic acid is 0.141, of lysine is 0.337 and of tyrosine is 0.093 and wherein the process includes determining the molecular weight distribution of a batch of an aqueous mixture of polypeptides, each of which consists essentially of alanine, glutamic acid, tyrosine and lysine, using a gel permeation chromatography column to determine whether the mixture has an average molecular weight from 4000 to 13,000 Daltons for inclusion in the pharmaceutical product, the improvement comprising calibrating the molecular weight obtained using the gel permeation chromatography column by subjecting a plurality of molecular weight markers, each of which is a polypeptide consisting essentially of alanine, glutamic acid, tyrosine and lysine and having a predetermined amino acid sequence, to chromatography on the column to establish a relationship between retention time on the column and molecular weight.