[Human serum albumin: microheterogeneity and hemin-binding ability].

Microheterogeneity of human serum albumin was studied by isoelectric focussing in ampholines and the borax-borate buffer-mannite system within the pH range 4.0--6.0 and by fractional precipitation in 3 M KCl. Albumin was found to have the same degree of heterogeneity in all separating systems. However, during focussing in ampholines microheterogeneity is partially due to the albumin binding with the ampholines. In other systems similar binding was not observed. Studies of the albumin-hemin complex showed that different fractions bind hemin in a different degree, maximal binding being observed within the pH range of 5.0--5.2. Defatting does not affect the distribution of hemin within the fractions of serum albumin.