Results are presented for proteins with known three-dimensional structure (lysozyme, myoglobin, ribonuclease), which show that the probability of label incorporation upon bombardment by "hot" tritium atoms may be quantitatively linked with the surface area of the protein accessible to water molecules. Possible deviations from simple linear dependency caused by particular mechanisms of label introduction are discussed. The data obtained in experiments with model systems were used to determine the accessible surface area of human serum albumin, for which structural data is not sufficiently accurate to allow estimation of accessible surface area. Experimental data correlate reasonably well with estimations based on conventional concepts of the relationship between accessible surface area and molecular weight for globular proteins.

SynopsisA study has been made of the heats of swelling of macronet isoporous polymers of styrene in toluene and methanol. The swelling of hypercrosslinked networks (degree of crosslinking 240%) is shown to be accompanied by liberation of large amounts of heat: 30 and 25 cal/g, respectively. The small difference in the heats of swelling in these media is indicative of small differences in the energy of dispersional interactions of exposed polystyrene chains with "good" and "poor" solvents. This conclusion is corroborated by calculations of the free energy of interaction between hypercrosslinked networks and organic solvents from the isotherms of sorption of their vapors. AG reaches high values (500-600 cal/mol) independently of the solvent nature.

No abstract

Abstract. The atomic dynamics of ultrafine clusters of y-ferric oxide with diameters of 1-3 nm, obtained by thermal decomposition of ferric oxalate, has been studied by gamma-resonance (Mossbauer) spectroscopy and by thermodynamic analysis. The intracluster atomic mobility has been shown to increase by the action of surfactants. Thermodynamical and phenomenological cluster models describing the dynamic state of clusters have been developed and are compared with the experimental data. The conditions for formation of a specific solid-liquid state of clusters are discussed.

No abstract