Molecular Dynamics Simulation Study of Interaction between Model Rough Hydrophobic Surfaces

摘要

We study some aspects of hydrophobic interaction between molecular rough andflexible model surfaces. The model we use in this work is based on a model weused previously (Eun, C.; Berkowitz, M. L. J. Phys. Chem. B 2009, 113,13222-13228), when we studied the interaction between model patches of lipidmembranes. Our original model consisted of two graphene plates with attachedpolar headgroups; the plates were immersed in a water bath. The interactionbetween such plates can be considered as an example of a hydrophilicinteraction. In the present work we modify our previous model by removing thecharge from the zwitterionic headgroups. As a result of this procedure, theplate character changes; it becomes hydrophobic. By separating the totalinteraction (or potential of mean force, PMF) between plates into the directand the water-mediated interactions we observe that the latter changes fromrepulsive to attractive, clearly emphasizing the important role of water as amedium. We also investigate the effect of roughness and flexibility of theheadgroups on the interaction between plates and observe that roughnessenhances the character of the hydrophobic interaction. The presence of adewetting transition in a confined space between charge-removed plates confirmsthat the interaction between plates is strongly hydrophobic. In addition, wenotice that there is a shallow local minimum in the PMF in case ofcharge-removed plates. We find that this minimum is associated with theconfigurational changes that flexible headgroups undergo, as the two plates arebrought together.