Interfacial residues

In our simulations, we performed association studies to elucidate their role by selecting pairs of those hot spot residues that established a barnase-barstar contact in the bound complex. In these simulations, we studied what effect the side-chain conformation had on contact formation for certain hot spot residue pairs. A typical result is shown in Figure 8. Starting from the correct rotameric state for certain hot spot residue pairs with the rest of the proteins in their unbound conformations leads to improved contact formation in the initial docking phase. This effect is not observed when performing equivalent simulations with non-hot-spot interfacial residue pairs. 

Shultz, M. D., and Chmielewski, J. (1999) Probing the role of interfacial residues in a dimerization inhibitor of HIV-1 protease. Bioorg. Med. Chem. Lett. 9, 2431-2436. 

The new procedure for determination of the structure of protein-protein complexes using saturation transfer and dipolar couplings has been constructed by Nakamura an co-workers.The SAT and RDC data provide information on the interfacial residues and the relative orientations of the two protein molecules. Docking simulation is then made to reconstruct a complex conformation, which satisfies the experimental data. 

While hydrophobicity is (whatever its origin) certainly an important force that guides the recognition of a protein and its substrate, water seems also to be important for the interaction of hydrophilic regions of such complexes. Around 70% of interfacial residues are in fact hydrophilic. It is common to assume that such polar groups experience a direct electrostatic interaction mediated by the (continuum) solvent. But in fact the water network has a more complex role here too. For example, in the formation of the complex between the bacterial ribonuclease bamase and its inhibitor barstar, water molecules mediate and stabilize the hydrophilic interactions between receptor and substrate at the granular level [60]. 

Fig. 25. Interfacial residual stresses along -direction due to elastic-plastic behavior V, = 36%) [110].

A reasonably close match of thermal expansion of the coating and substrate over a wide temperature range to limit failure caused by residual stresses is desired for coatings. Because temperature gradients cause stress even in a weU-matched system, the mechanical properties, strength, and ductUity of the coating as well as the interfacial strength must be considered. 

Film Adhesion. The adhesion of an inorganic thin film to a surface depends on the deformation and fracture modes associated with the failure (4). The strength of the adhesion depends on the mechanical properties of the substrate surface, fracture toughness of the interfacial material, and the appHed stress. Adhesion failure can occur owiag to mechanical stressing, corrosion, or diffusion of interfacial species away from the interface. The failure can be exacerbated by residual stresses in the film, a low fracture toughness of the interfacial material, or the chemical and thermal environment or species in the substrate, such as gases, that can diffuse to the interface. 

Fig. 9. Residual stresses owing to thermal expansion mismatch between a particle with radius a and thermal expansion coefficient and a matrix with thermal expansion coefficient The stresses illustrated here are for and P is the interfacial pressure.

All these results are consistent with the hypothesis that aryl cations react in aqueous media at diffusion-controlled rates with all nucleophiles that are available in the immediate neighbourhood of the diazonium ion. On this basis Romsted and coworkers (Chaudhuri et al., 1993a, 1993b) used dediazoniation reactions as probes of the interfacial composition of association colloids. These authors determined product yields from dediazoniation of two arenediazonium tetrafluoroborates containing ft-hexadecyl residues (8.15 and 8.16) and the corresponding diazonium salts with methyl groups instead of Ci6H33 chains. ... 

Studies on mechanisms are described by Balzer [192]. In the case of anionics the residual oil in the injection zone is removed via displacement into the adjacent reservoirs ether carboxylates show their good adaptation to differences in temperature and salinity. Further it was found from interfacial tension measurements, adsorption and retention studies, and flooding tests that use of surfactant blends based on ether carboxylates and alkylbenzensulfonates resulted... 

FIGURE 6.2 Interfacial tension imprisons residual oil in rock, preventing its displacement by water. Without interfacial tension, oil flows freely, leaving no residual portion in the rock. Courtesy, Amoco Production Company. 

This assumption was supported by the fact that the residual current observed by potential scan polarography at the W/DCE interface was larger in Range C than that in other ranges, indicating the increase of the capacitance due to the change of the interfacial structure. 

---