Proteins are one of the central molecules in living systems. A variety of structures and functions of proteins are essential for vital activities. Because of the sophisticated functions involved in the wide range of biological events, proteins are also important molecules for the development of pharmaceuticals and biofunctional materials. The biological functions of proteins originate from the higher-order structures of the polypeptide chains forming the native structures. Collapse of the native structures causes denaturation and aggregation of the proteins, which results in loss of the biological functions irreversibly.

Enhancement of protein stability against environmental factors such as changes in pH,...