Three-body hydrophobic interactions

Moghaddam et al.111 discuss the consequences of three-body hydrophobic interactions on properties of a system consisting of methane-like nonpolar solutes in water. The implications of their findings on understanding protein folding are considered in detail. 

A surprising result that emerged from the earlier work on hydrophobic interactions is that there is little or no tendency for nonpolar solute association at low concentration. For example, simulation results led Watanabe and Andersen to discuss the hydrophobic repulsion between krypton atoms in water.Calculated PMFs have typically supported a similar conclusion (discussed below). Aggregation of methane in water was observed to occur at higher concentrations, " suggesting that there may be cooperative aspects to the solute aggregation process. This conflicts, however, with results from Shimizu and Chan who explicitly observed anticooperativity in three-body hydrophobic interactions. ... 

Interactions of monomer units that are far apart in a polymer chain of a gel can be represented as a sum of two- and three-body interactions. Such interactions involve monomer-solvent and solvent-solvent interactions but not hydrophobic interactions. 

Realistic three-dimensional computer models for water were proposed already more than 30 years ago (16). However, even relatively simple effective water model potentials based on point charges and Leimard-Jones interactions are still very expensive computationally. Significant progress with respect to the models ability to describe water s thermodynamic, structural, and dynamic features accurately has been achieved recently (101-103). However, early studies have shown that water models essentially capture the effects of hydrophobic hydration and interaction on a near quantitative level (81, 82, 104). Recent simulations suggest that the exact size of the solvation entropy of hydrophobic particles is related to the ability of the water models to account for water s thermodynamic anomalous behavior (105-108). Because the hydrophobic interaction is inherently a multibody interaction (105), it has been suggested to compute pair- and higher-order contributions from realistic computer simulations. However, currently it is inconclusive whether three-body effects are cooperative or anticooperative (109). 

Czaplewski C, Rodziewicz-Motowidlo S, Liwo A, Ripoli DR, Wawak RJ, Scheraga HA. Comment on anti-cooperativity in hydrophobic interactions A simulation study of spatial dependence of three-body effects and beyond . J. Chem. Phys. 2002 116 2665-2667. 

Oleosins have unique secondary structures that enable the proteins to interact with other molecules on the surface of oil bodies. Each oleosin molecule has three structural domains an N-terminal amphipathic domain, a central antiparallel p-stranded hydrophobic domain, and a C-terminal amphipathic domain. The central domain anchors the protein onto the oil body or in the lipid-containing organelles, whereas the N-terminal and C-terminal domains are exposed to the exterior. Among oleosins of different organs and plant species, only the central hydrophobic stretches (72 residues) are highly conserved, whereas the N-terminal and C-terminal sequences are quite dissimilar. 

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