CHEMICAL, CLINICAL, AND IMMUNOLOGICAL STUDIES ON THE PRODUCTS OF HUMAN PLASMA FRACTIONATION. IV. A STUDY OF THE THERMAL STABILITY OF HUMAN SERUM ALBUMIN 123

Abstract

The thermal stability of standard commercial human serum albumin and of crystalline material was studied by measuring the turbidity at 50[degree] and 57[degree]C, and the viscosity at 55[degree] and 57[degree]C. The stability is defined as the reciprocal of the time necessary for an increase of 20 nephelometric units, or for an increase of 5-10% in viscosity. The stability is approx. proportional to the conc. of NaCl, at least to 0.6 M. It decreases with increasing albumin conc. There is a maximum in the stability at pH about 6.8, so flat that the stability decreases not more than 10% for pH''s within 0.2 of the maximum. Merthiolate appears to have no effect on stability. Storage for long periods at 25[degree] or at 37[degree] has very little effect on the turbidity or the viscosity, but it does decrease the stability on subsequent heating to higher temps. These expts. and others on the filtration of heated solns. indicate that the changes in size which cause the turbidity are preceded by changes in shape which increase the viscosity, and that the very first change affects neither of the methods of measurement. The commercial prepns. contain 25% albumin and 1.8% NaCl at a pH of 6.8 [plus or minus] 0.2. For an increase of 20 nephelometric units they -require about 80 hrs. at 57[degree] and about as many days at 50[degree]C. The time of gelation is about 3 times that for an increase of 20 nephelometer units.