ELECTROSPRAY-IONIZATION MASS ANALYSIS OF NORMAL AND GENETIC-VARIANTS OF HUMAN SERUM-ALBUMIN

Both normal albumin (Al A) and genetically modified forms were isolate d from six heterozygous subjects. Albumins from each individual were a nalyzed by electrospray ionization mass spectrometry (ESI MS), and the mass was compared with that predicted from the protein sequence. In a ll cases, the Al A was heterogeneous, with components of mass (+/- SE) 66 463 +/- 4, 66 586 +/- 3, and 66 718 +/- 5 Da. Each genetic variant showed similar heterogeneity. The mass increase in Al Casebrook (2214 Da) was very close to that predicted (2205 Da) from protein and carbo hydrate sequence analysis, whereas the increase in Al Redhill (2378 Da ) was close to that expected (2392 Da) for an Arg-albumin with a disia lylated N-linked biantennary oligosaccharide and an Ala-->Thr mutation . The circulating proalbumins, Christchurch and Blenheim, had mass inc reases of 748 and 756 Da, respectively, over Al A; in excellent agreem ent with theoretical values of 744 and 756. Clear shifts in mass were also detected for the point substitutions 177Cys-->Phe (44 Da), 1Asp-- >Val (20 Da), and Arg-albumin (160 Da).