Thermodynamics of extensive interfaces between rigid, apolar walls and water.

A simple set of equations is proposed to govern the relations between the thermodynamic potentials in rigid, apolar wall-water systems, which is found to be consistent with the data for two systems: alkane plate-SPC/E water [R. Zangi and B. J. Berne, J. Phys. Chem. B 112(29), 8634-8644 (2008)] and graphene plate-TIP4P/Ew water [R. Zangi, J. Phys. Chem. B 115, 2303-2311 (2011)]. These data exhibit exact compensation of enthalpy and entropy for the water-water interactions. Surface tension of the free water surface is the invariant excess free energy per unit area for the water phase in these wall-water systems at thermodynamic equilibrium.

On interfacial tension at a rigid apolar wall-water interface.

Evidence is presented that the interfacial tension or excess free energy per unit area of the planar interface between extensive, rigid, apolar walls and modeled water is an arithmetic sum of three independent quantities: the surface tension of water, the contribution of the integrated wall-water dispersion interaction, and the contribution of the net exclusion volume associated with the rigid, noninteracting wall. The fact that the interfacial tension is linearly dependent on the wall-water interaction parameter is the inspiration for two conjectures: the interfacial water structure is independent of ε(SL), and the mean interfacial water density profile is not a measure of the interfacial water structure.

TEM immunogold staining of C3 from plasma onto titanium oxides.

Immunogold staining in conjunction with TEM was used to observe C3 adsorption from plasma in relation to the underlying titanium structure of thermal, anodic, and electropolished oxides. Heat treatments and oxide thickness were found to have no significant effect on the adsorption behavior of C3, while surface oxide type possibly has. Surface concentration of C3 was found to be time- and plasma concentration-dependent. Evidence is given for the possible involvement of C3 in protein exchange, i.e., the Vroman effect. Diluted plasma resulted in a random distribution of gold colloids, whereas clustering occurred with undiluted plasma. Although C3 concentrations present on grain boundaries followed the same trend as that found on the surface, C3 was found to have a higher grain boundary than bulk concentration for 0.1% plasma.

Field ion microscopy of biomolecules.

A new type of image, existing only at field strengths below the denaturation field strengths of molecules, has been discorvered. This type of image has structure, is not symmetrical and thus differs from previously reported low field strength images. The possibility that macromolecules adsorbed on tip surfaces produce such structured images has been exhaustively investigated. The result is that no observation has been found which disproves this hypothesis and many tests conducted in such attempts yielded correlations consistent with this hypothesis. It is therefore concluded that it is highly probable that biomolecules produce structured images and that it is highly improbable that these correlations represent a chance event. On the other hand, these correlations may be due to some cause unknown to the authors; but we consider this possibility to be unlikely. Some micrographs have been obtained which provide a reasonable basis for the hope that tertiary structure information may be defrived from low field strength imaging of partially embedded biomolecules or of biomolecules that are resistant to field denaturation during imaging. Information may presently be obtained from analysis of low field strength ion micrographs about the size and shape of some biomolecules.