In the case of thioamides, the decrease in solubility can be explained by their decreased hydrogen bonding ability, as well as their increased interaction with nonpolar regions on the polymer. This effect has been demonstrated by Khatri et al. in a report which explored how thioamide insertion increases protein stability. In this study, sulfur-substituted variants of proteins were prepared, and thionated proteins were examined to understand the effects of thionation at a molecular level.