Liquid solutions residual functions

Figure 2.5 Critical volume fractions < i below which a solution of poly(benzyl-L-glutamate) is fully isotropic (O) and 2 above which the solution is fully liquid crystalline ( ) as functions of the number of peptide residues N in the chain. The molecular contour length is roughly 1.5N A. (From Robinson et al. 1958, reproduced by permission of The Royal Society of Chemistry.)...

A complete set of intermolecular potential functions has been developed for use in computer simulations of proteins in their native environment. Parameters have been reported for 25 peptide residues as well as the common neutral and charged terminal groups. The potential functions have the simple Coulomb plus Lennard-Jones form and are compatible with the widely used models for water, TIP4P, TIP3P and SPC. The parameters were obtained and tested primarily in conjunction with Monte Carlo statistical mechanics simulations of 36 pure organic liquids and numerous aqueous solutions of organic ions representative of subunits in the side chains and backbones of proteins... 

The presence of surface OH groups or H2 O molecules can play a primary role in adsorption. For example, a microcalorimetric study of the adsorption of stearic acid, from heptane solution, on ferric oxide (Husbands et al., 1971) revealed that preadsorbed water enhanced adsorption of stearic acid. When adsorption takes place from a dry organic liquid, residual surface water may act as special agent. This was shown for the adsorption of a silane coupling agent (y-amino-propyl-triethoxysilane) on silica covered with water molecules for 6 < 1 (Trens and Denoyel, 1996). By the simultaneous determination of adsorption isotherms and the enthalpies of displacement (of heptane by various silanes) it was demonstrated that the amine function was able to displace some of the surface water and make it available for the hydrolysis of the silane into trisilanol, whereas the residual water was able to promote the formation of siloxane bonds between the trisilanol molecules and the surface. 

Liquid crystals can also be used since the temperature-dependent residual static dipole-dipole coupling caused by the anisotropic orientational order produces, in turn, a temperature-dependent static splitting of the proton spectrum. The first study used a 5% v/v solution of benzene in the room temperature mesophase ZLI-1132 liquid crystal in a 5 mm NMR tube. Over 60 lines were present in the spectrum (66 at 360 MHz and 64 at 600 MHz). The authors measured the frequency separation of the outermost lines as a function of temperature at 360 MHz, and fitted this to a third-order polynomial, giving ... 

In solution crystallization product purity is controlled to a great extent by the efficiency of solid-liquid separation. Impurities dissolved in the ciystallizer liquid are normally removed by spinning liquor from the crystals and then washing the resulting cake. The residual impurity level is a function of factors listed in the following equation ... 

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