Role of hydration and water structure in biological and colloidal interactions

Abstract

The conventional explanation of why hydrophilic surfaces and macromolecules remain well separated in water is that they experience a monotonically repulsive hydration force owing to structuring of water molecules at the surfaces. A consideration of recent experimental and theoretical results suggests an alternative interpretation in which hydration forces are either attractive or oscillatory, and where repulsions have a totally different origin. Further experiments are needed to distinguish between these possibilities.

On the Application of Accelerated Molecular Dynamics to Liquid Water Simulations

“…Equation 1 shows the relation among the unmodified, modified and boost energy. (1) In this work, ΔV(r) is defined by equation 2, according to the implementation proposed by Hamelberg et al 12 (2) where α is a tuning parameter that controls the depth of the energy basins on the modified potential. Figure 1 illustrates the effect of the equation 2 on a hypothetical one-dimensional potential function V(r).…”

Direct mapping of the solid–liquid adhesion energy with subnanometre resolution

“…However, specialized instruments were used and the nature of the tip-sample interaction remains an issue of debate. Dynamic AFM has the ability to probe the solid-liquid interface [18][19][20][21] , but an interpretation of experimental results remains difficult 22,23 . Traditionally, interfaces are characterized by an interfacial energy, IE, the sum of the two surface energies in vacuum minus the work of adhesion (W SL ) necessary to separate the surfaces (Dupré Equation 24 ).…”

“…At the molecular level the presence of the solid affects liquid molecules near the solid's surface 6,25 through so-called solvation or structural forces 26 . These forces are generally of relatively short range and strongly dependent on the local nature of the solid, thus limiting the interfacial liquid to extend only a few molecular diameters away from the surface 6,22,26 . AFM has allowed direct probing of the density variations at the interfacial layer as a function of distance from the interface for confined liquid layers at the surface of both hard 20 and biological materials 21 .…”

Application and use of differential scanning calorimetry in studies of thermal fluctuation associated with amyloid fibril formation

“…In the model, the transient association is thermally induced by hydrophobic interaction due to hydrophobic residues packed regularly along the fibril structure. Hydrophobic interactions usually play an important role in thermally induced aggregation of protein molecules, the basic features of which are assumed to be the spatial approach and dehydration of the exposed hydrophobic regions to solvent water (Kauzmann 1959;Tanford 1978;Baldwin 1986;Israelachvili and Wennerström 1996;Chandler 2005). In the amyloid fibrils formed from β 2 -m and Aβ, the hydrophobic and hydrophilic residues may be patterned on the fibril surface (Broome and Hecht 2000;Mandel-Gutfreund and Gregoret 2002;Hecht et al 2004;Saiki et al 2005;Fändrich et al 2009;Bowerman and Nilsson 2012), resulting in transient association upon heating.…”