Journal of Lipid Research, Vol. 11, 195-200, May 1970
Copyright © 1970 by Lipid Research, Inc.

Solution of fatty acids from monolayers spread at the air-water interface: identification of phase transformations and the estimation of surface charge

Richard E. Heikkila , David W. Deamer , and David G. Cornwell

Department of Physiological Chemistry, The Ohio State University, Columbus, Ohio 43210

The contraction or decrease in area of fatty acid monolayers maintained at a constant surface pressure of 16 dynes/cm was studied as a function of fatty acid chain length, unsaturation, temperature, and the hydrogen ion concentration in the subphase. The data were consistent with the hypothesis that fatty acid solution from the monolayer into the subphase was the mechanism for film loss. Autoxidative reactions did not contribute significantly to film loss since contraction occurred with saturated fatty acid monolayers and with unsaturated fatty acid monolayers in an anaerobic environment. The decrease in area per unit time or the solution rate was inversely proportional to chain length and directly proportional to the degree of unsaturation. Arrhenius plots showed activation energies of 1.5-2.5 kcal mole^-1 for tetradecanoic, octadecenoic, and octadecadienoic acids, and 25 kcal mole^-1 for hexadecanoic acid. The solution rate from the monolayer increased in a sigmoidal fashion with an increase in subphase pH, and the apparent surface pK_a was estimated as the point where the solution rate was half-maximum. Apparent surface pK_a values were: hexadecanoic acid, 9.7; octadecenoic acid, 8.3; tetradecanoic acid, 7.9; and octadecadienoic acid, 8.0.

Supplementary key words surface film • surface pressure • surface pH • apparent surface pK_a • temperature • solubility • activation energy • autoxidation • tetradecanoic • hexadecanoic • octadecanoic • octadecenoic • octadecadienoic

Submitted on October 14, 1969
Accepted on January 19, 1970

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				E. C. Smith, J. M. Crane, T. G. Laderas, and S. B. Hall Metastability of a Supercompressed Fluid Monolayer Biophys. J., November 1, 2003; 85(5): 3048 - 3057. [Abstract] [Full Text] [PDF]

				W. Schmider, A. Fahr, H. E. Blum, and G. Kurz Transport of heptafluorostearate across model membranes. Membrane transport of long-chain fatty acid anions I J. Lipid Res., May 1, 2000; 41(5): 775 - 787. [Abstract] [Full Text]