Hydration and Nanoconfined Water: Insights from Computer Simulations

LAUREANO ALARCON; J. ARIEL RODRÍGUEZ FRIS; MARCELA A. MORINI; MARIA B. SIERRA; SEBASTIÁN R. ACCORDINO; JOAN MONTES DE OCA; VIVIANA I. PEDRONI; GUSTAVO A. APPIGNANESI

Membrane Hydration: The Role of Water in the Structure and Function of Biological Membranes

Springer International Publishing AG Switzerland is part of Springer Science+Business Media

Año: 2015; p. 161 - 187

The comprehension of the structure and behavior of water at interfacesand under nanoconfinement represents an issue of major concern in several centralresearch areas like hydration, reaction dynamics and biology. From one side, wateris known to play a dominant role in the structuring, the dynamics and the functionalityof biological molecules, governingmain processes like protein folding, proteinbinding and biological function. In turn, the same principles that rule biologicalorganization at the molecular level are also operative for materials science processesthat take place within a water environment, being responsible for the self-assemblyof molecular structures to create synthetic supramolecular nanometrically-sizedmaterials. Thus, the understanding of the principles of water hydration, including thedevelopment of a theory of hydrophobicity at the nanoscale, is imperative both froma fundamental and an applied standpoint. In this work we present some moleculardynamics studies of the structure and dynamics of water at different interfaces orconfinement conditions, ranging from simple model hydrophobic interfaces withdifferent geometrical constraints (in order to single out curvature effects), to selfassembledmonolayers, proteins and phospholipid membranes. The tendency of thewatermolecules to sacrifice the lowest hydrogen bond (HB) coordination as possibleat extended interfaces is revealed. This fact makes the first hydration layers to behighly oriented, in some situations even resembling the structure of hexagonal ice. Asimilar trend to maximize the number of HBs is shown to hold in cavity filling, withsmall subnanometric hydrophobic cavities remaining empty while larger cavitiesdisplay an alternation of filled and dry states with a significant inner HB network.We also study interfaces with complex chemical and geometrical nature in orderto determine how different conditions affect the local hydration properties. Thus,we show some results for protein hydration and, particularly, some preliminarystudies on membrane hydration. Finally, calculations of a local hydrophobicitymeasure of relevance for binding and self-assembly are also presented. We thenconclude with a few words of further emphasis on the relevance of this kindof knowledge to biology and to the design of new materials by highlighting thecontext-dependent and non-additive nature of different non-covalent interactions inan aqueous nanoenvironment, an issue that is usually greatly overlooked.