Molecular Insight into Different Denaturing Efficiency of Urea, Guanidinium, and Methanol: A Comparative Simulation...

We have designed various nanoslit systems, whose opposing surfaces can be either hydrophobic, hydrophilic, or simply a water-vapor interface, for the molecular dynamics simulation of confined water with three different protein denaturants, i.e., urea, guanidinium chloride (GdmCl), and methanol, respectively. Particular attention is placed on the preferential adsorption of the denaturant molecules onto the opposing surfaces and associated resident time in the vicinal layer next to the surfaces, as well as their implication in the denaturing efficiency of different denaturant molecules. Our simulation results show that among the three denaturants, the occupancy of methanol in the vicinal layer is the highest while the residence time of Gdm is the longest. Although the occupancy and the residence time of urea in the vicinal layer is less than those of the other two denaturant molecules, urea entails "all-around" properties for being a highly effective denaturant. The distinct characteristics of three denaturants may suggest a different molecular mechanism for the protein denaturation. This comparative simulation by design allows us to gain additional insights, on the molecular level, into the denaturation effect and related hydrophobic effect.