[Molecular ageing in bovine plasma albumin I. Exposure of disulfide bonds in the N-B transition (author's transl)].

An accessibility of the disulfide bonds of defatted SH-blocked bovine plasma albumin (BPA) to reduction by dithiothreitol was studied at 4 degree C. Upon reduction SH-blocked BPA acquired one SH per mole in the pH range from 4.0 to 6.0. Above pH 6.5 (the pH range of the N-B transition) an increasing number of the disulfide bonds became susceptible to reduction by dithiothreitol. Chemicals, such as KC1, fatty acid, sodium dodecylsulfate which suppress the structural fluctuation of BPA in the alkaline region decreased the accessibility of the disulfide bonds to reduction. The conversion of buried disulfide bonds into exposed ones is interpreted as being due to conformational changes in the N-B transition (pH 7.0 approximately 9.0).