Salt and pH-dependent properties of native and mutant insulin

A fast and effective model for predicting the salt and pH dependent properties of protein complexes is presented. It is based on the formal charge parameter sets of ionizable groups and applied in conjunction with the finite difference Poisson-Boltzmann (FDPB) method to calculate the electrostatic interactions. All simulations were performed on the native 2Zn insulin and its fast-acting mutants such as B9D (B9Ser→ Asp), B9E (B9Aer→ Giu), B9EB10D (B9Ser→Glu, B10His→ Asp), and B10D (B10His → Asp). The salt and pH dependent properties of these dimers were analyzed from the aspect of electrostatic interaction, and the theoretical basis of the fast-acting behavior of these mutants was explained. It is found that the results agree well with experimental observations.