The Process of Dissolving Apolipoprotein A-I in an Aqueous Buffer1

Abstract

Human plasma apolipoprotein A-I (apoA-I) has been studied in an aqueous solution by the techniques of high performance liquid chromatography (HPLC), circular dichroic spectroscopy, and sedimentation equilibrium ultracentrifugation. The results indicate that an oligomer is formed as an intermediate step of dissolving lyophilized apoA-I. The process of further dissolution of this oligomer is an irreversible, temperature-dependent dissociation. The half-life of this intermediate oligomer is 3 min at 37°C and 80 h at 30°C. The completely dissolved apoA-I in an aqueous buffer self-associates with conformational alteration. The self-association equilibrium is too rapid to be demonstrated by HPLC.