Cryoprotection of protein by highly concentrated branched oligosaccharides

Abstract

Abstract Cryoprotection of protein by highly concentrated branched oligosaccharides (HBOS) was investigated by using a model solution containing bovine serum albumin (BSA). The glass transition temperature of the BSA solution with HBOS, determined by modulated differential scanning calorimetry, was −16.1 °C, which is higher than that of sucrose at either 4 or 8% concentration by weight (−27.2 °C). Also, changes in the unfrozen water fraction and their mobilities, determined by nuclear magnetic resonance, were used as indices of protein stabilization. The results revealed that the amount of unfrozen water increased whereas the mobility was decreased by addition of HBOS. Thus we propose that the cryoprotection effect can occur by preserving the protein in a rigid structure formed by the water and the cryoprotectant HBOS.