Hydrogen-bonding interactions interfaces

There is a fair amount of work reported with films at the mercury-air interface. Rice and co-workers [107] used grazing incidence x-ray diffraction to determine that a crystalline stearic acid monolayer induces order in the Hg substrate. Quinone derivatives spread at the mercury-n-hexane interface form crystalline structures governed primarily by hydrogen bonding interactions [108]. 

AOT is an anionic surfactant complexed to the counterion, usually sodium. The water molecules in the intramicellar water pool are either free or bound to the interface. The bound water can interact with various parts of the surfactant. These interactions include hydrogen-bonding interactions with oxygen molecules on the sulfonate and succinate groups, ion-dipole interactions with the anionic surfactant headgroup and counterion, dipole-dipole interactions with the succinate group, and dispersive forces with the hydrocarbon tails. 

All molecules in a liquid phase interact with each other and exert a force on neighboring molecules. We have already discussed the hydrogen-bonding interaction of water molecules that creates clusters. The water molecules at a gas-liquid interface, however, are exposed to unequal forces, and are attracted to the bulk water of the liquid phase because no attraction is exerted on them from the direction of the gas phase. This accounts for the surface tension of liquids. 

Analysis of the crystallographic structure also reveals that the two domains interact primarily through hydrophobic and hydrogen bond interactions at the interface. The number of apolar hydrogens that become exposed on the C domain on unfolding of the N domain is 49.4, and the number of apolar hydrogens exposed on the N domain on unfolding of the C domain is 44.8. These values correspond to 726 and 659 A2 of apolar surface area, respectively. In addition, nine... 

FIGURE 12.9. A schematic illustration of molecular recognition mediated by hydrogen-bonding interactions at a liquid/liquid interface. 

Clearly, the solvent has an effect on the properties of the protein. Addition of solvent eliminates the protein—vacuum interface and thus the shrinking of the protein found in vacuo. The hydrogen-bonding interactions possible with solvent eliminate nonnative interactions found in vacuo, presumably through offering alternative and solvated native protein-like bonding arrangements. 

In their native conformation, globular proteins have non-polar amino acid side chains oriented towards the interior of the protein and polar side chains oriented outwards, towards the solvent. The stability of the native conformation is determined by hydrophobic interactions within the interior of the molecule, and electrostatic interactions and hydrogen bond interactions at the protein-water interface. Disturbing these interactions can alter the balance between the intra- and intermole-cular interactions, which are responsible for maintaining the protein in soluble... 

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