N o~i o NISH~MURA, TOHRU TANAKA, and TAKUSH~ MOTOYAMA. Can. J. Chem. 65, 2248Chem. 65, (1987. A critical test of additivity for partial molar volume has been made at 25' C in CCI4 with polyethylene glycol dimethyl ethers, crown ethers, cycloalkanes, n-alkanes, and others. Plots of partial molar volume at infinite dilution (v O ) against the properly chosen number of repeating unit ( n ) are linear except for small cyclic molecules, and the slopes of homologous straight chain and ring compounds are the same. The values of v O extrapolated to 11 = 0 for cycloalkanes and crown ethers support the validity of the contribution due to the translational kinetic energy that has been predicted recently on a theoretical basis. The importance of packing efficiencies around the solute molecules has been examined by means of simple models.NORIO NISHIMURA, TOHRU TANAKA et TAKUSH~ MOTOYAMA. Can. J. Chem. 65,2248Chem. 65, (1987. OpCrant i 25"C, dans des solutions de CC14, on a effectuC une Cvaluation critique de I'additivitC des volumes molaires partiels pour des Cthers dimtthyliques du polyCthylkne glycol, des Cthers couronnes, des cycloalcanes, des n-alcanes et d'autres composCs. A l'exception des molCcules contenant des petits cycles, on a trouvC qu'il existe une relation linCaire entre les volumes molaires partiels i dilution infinie (a O) et le nombre choisi appropriC d'unitts periodiques (n); de plus, les pentes des courbes pour les composCs homologues aliphatiques sont les mkmes que celles pour les composts cycliques. Pour les cycloalcanes et pour les Cthers couronnes, les valeurs de (v O ) extrapolCes i n = 0 sont en accord avec la prCdiction qui a rCcemment CtC faite sur une base thCorique et selon laquelle on pr6voit une contribution de la part de 1'Cnergie cinCtique de translation. Utilisant des moddes simples, on a CtudiC I'importance des efficacitCs d'empilement autour des moltcules de solutCs.[Traduit par la revue]

No abstract

No abstract

The possible involvement of G-proteins in cold-sensory transduction was examined using voltage-clamped Paramecium multimicronucleatum into which non-hydrolyzable guanosine nucleotide analogues had been applied intracellularly. Guanosine-5'-O-3-thiotriphosphate, guanosine-5'-O-2-thiodiphosphate and aluminium fluoride all reduced the transient inward current in response to cooling, suggesting the possibility that G-proteins mediate cold-sensory transduction. Internal application of a Ca2+ chelator, EGTA, also reduced the current response. In addition to their effect on reducing the cold-sensory response, application of these chemicals modulated both the resting potential and the membrane conductance. Possible correlations between G-protein activity and the regulation of intracellular Ca2+ levels are discussed.