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Biomedical subjects

C Tanford

Publications and source records attributed to C Tanford.

At least 73 records · Page 4Linked to original sources
PubMed1974

Thermodynamics of micelle formation: prediction of micelle size and size distribution.

This paper presents a simple theory for the calculation of micelle size and other properties of micelleforming systems. The theory is based on the separate estimation of the components of the free energy arising from hydrophobic attraction and from head group repulsion, each as a function of micelle size. The difficult problem of an a priori calculation of the repulsive factor is circumvented by using experimental values of this parameter, derived from pressure-area curves of monolayers at an interface between an aqueous solution and liquid hydrocarbon. Though some parameters of the theory are still somewhat uncertain, self-consistent and physically realistic values can be assigned that lead to almost exact prediction of experimental micelle sizes and critical micelle concentrations for two distinctly different ionic detergents.

Lipids↗
PubMed1974

Empirical correlation between hydrophobic free energy and aqueous cavity surface area.

The unitary free energy of transfer of a hydrocarbon molecule from a hydrocarbon solvent to an aqueous medium is a measure of the hydrophobic interaction in the aqueous medium. We have reexamined available data on this phenomenon and have confirmed that the free energy for saturated hydrocarbons is proportional to the surface area of the cavity created by the solute in the aqueous solution, with the same proportionality constant for linear, branched, and cyclic hydrocarbon molecules. The numerical value of the proportionality constant is uncertain because absolute and self-consistent area measurements are not available. We estimate that it falls between 20 and 25 cal/mole per A(2) at 25 degrees (for areas measured at the distance of closest approach of water molecules), which is significantly less than the figure of 33 cal/mole per A(2) that has been assigned to the same parameter by Hermann [J. Phys. Chem. 76, 2754-2759 (1972)]. A small discrepancy exists when similar data for homologous series of alkyl derivatives are compared with results based on hydrocarbons themselves, and possible reasons for it are discussed.

Journal Article↗
PubMed1973

Hydrophobicity of Long Chain n-Alkyl Carboxylic Acids, as Measured by Their Distribution Between Heptane and Aqueous Solutions.

Previous data for the distribution of the n-alkyl carboxylic acids between aqueous buffers and heptane have suggested that the free energy of transfer between the two solvents does not increase with the length of the alkyl chain beyond palmitic acid, indicating a limit to the hydrophobicity of the alkyl chain at a length of about 15 carbon atoms. It is shown in this paper that previous measurements were influenced by unexpectedly strong pH-dependent association of the long-chain acids in the aqueous phase. Under conditions where such association becomes negligible, the free energy of transfer becomes a strictly linear function of alkyl chain length for all acids up to behenic acid (C(21)H(43)COOH).

Journal Article↗