Human serum albumin is a single chain polypeptide which composes about 60% of the plasma proteins. In normal serum approximately 10% of the albumin is modified by non-enzymatic glycosylation which occurs primarily on lysine residue number 525 (Garlick & Mazer, J. Biol. Chem., 258, 6142-6146, 1983). The amount of glycosylated albumin in serum is markedly elevated in diabetes (Dolhofer & Wieland, Febs. Lett., 103, 282-286, 1979) and thus its determination may help in the monitoring of the disease. Studies also show that glycosylation of the protein alters its properties and this modification causes it to be ingested by endothelial cells in preference to unmodified albumin (Williams, et al, Proc. Natl. Acad. Sci, 78, 2393-2397, 1981).