Polymeric complexes and fragments of albumin in normal human plasma

Abstract

Nitrocellulose blots of normal human plasma proteins separated by sodium dodecyi sulfate-polyacrylamide gel electrophoresis were examined for polymeric complexes and fragments of albumin using an immunoperoxidase-labelled mouse monoclonal anti-human albumin antibody. Under reducing conditions, no polymeric complexes were seen. Under non-reducing conditions, polymeric complexes were detected at the following molecular weights: 210000, 168000, 147000, 132000, and 110000. These probably represent both homo- and heteropolymers of albumin. Fresh plasma samples were also analyzed by S-200 chromatography with the same results indicating that detection of polymeric complexes was not an artifact of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique. In quantitative terms, polymeric complexes constituted 0.3-2.8% of the total albumin present. Fragments of albumin were also seen in normal human plasma with molecular weights of 45000, 28000 and 19000. These fragments probably represent breakdown products of albumin in normal blood, and they constituted less than 2% of the total albumin present.