CRYSTALLOGRAPHIC STUDY ON HIGHLY STABLE HUMAN INSULINS——CRYSTALLIZATION AND PRELIMINARY CRYSTALLOGRAPHIC ANALYSIS OF A21-SER MUTANT

It has long been found that insulin in acid solution is unstable. The main reason is that the A-chain C-terminal residue, asparagine, is very susceptible to acid hydrolysis, thereby a covalent-dimer formation takes place readily due to the deamidation of this residue. As a number of pharmaceutical preparations of insulin are acidic solutions, this kind of instability has brought about a serious problem on purity and storage of this preparation in clinical