Evidence for a concentration-dependent polymerization of a commercial human serum albumin

Polymerization of a commercial human serum albumin (Sigma A-1887) was investigated by two different techniques, high-performance liquid chromatography and gel electrophoresis. The chromatographic technique was based on the frontal analysis principle using a column which excludes polymers but retains monomers. The results allowed the determination of the monomer--polymer affinity constant, X = 526 +/- 100. The electrophoresis technique was performed with a polyacrylamide gel containing sodium dodecyl sulphate in order to separate the different polymer species according to their molecular weights. The two techniques gave results in good accordance and showed a concentration-dependent aggregation. The higher the human serum albumin concentration, the more the monomer proportion decreases.