MD and DSC study of bioactive structural stability of insulin in various imidazolium ionic liquids

Ionic liquids (ILs) have been used as a kind of green solvents trying to preserve protein drugs for many years. However, the protective mechanism of ILs on protein drugs is still unclear, which limits their application. For this reason, a molecular dynamic simulation (MD) was used to investigate the structural stability of insulin in 17 ILs solvents, including 10 pure and 7 hydrated ILs systems. The results of molecular interaction between insulin and ILs indicate insulin is stable in pure ILs with lower hydrogen bond basicity and shorter alkyl chain. And while water content is less than 25.00%, the hydrated ILs also are favorable for protein conservation. Moreover, the micro-DSC experimental results prove that the thermal stability of insulin in hydrated [C2mim][OAC] also support the results of MD simulation. So it can be seen that the ILs with lower hydrogen bond basicity and shorter alkyl chain usually have a protective effect on protein, and the MD simulation provides a new and extraordinary method for screening the protective ILs.