TY - JOUR
T1 - Some micellar properties of long-chain acylcarnitines
AU - Yalkowsky, Samuel H.
AU - Zografi, George
N1 - Funding Information:
1 This study was supported in part by the Bristol-Myers Company, Hillside, New Jersey; General Research Support Grant FR 05571, National Institutes of Health, and United States Public Health Service Training Grant DE 00204, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland.
PY - 1970/12
Y1 - 1970/12
N2 - The acid dissociation constants of long-chain esters of carnitine (β-hydroxy-γ-trimethylammonium-butyrate) above the critical micelle concentration were determined potentiometrically at several concentrations of added KCl. As the degree of protonation β increases the apparent pK values decrease owing to the increased positive charge on the micelle. The difference in pK between the neutral (zwitterionic) micelle and the value at any given β was used to determine the surface potential of the micelle Ψ at that degree of protonation. At each degree of protonation the measured surface potential was related to the surface charge density σ with the aid of the calculations of Loeb, Wiersema, and Overbeek for a spherical impenetrable particle. The surface potentials and surface charge densities of lauryl-, myristyl-, and palmitylcarnitine are nearly identical at a given degree of protonation and ionic strength, and, as expected, increasing the ionic strength produces a decrease in the surface potential. From the partial molal volume of each surfactant in the micelle and the calculated surface charge density it was possible to calculate the aggregation number n of the micelle. Good agreement was found between the calculated values of n and values obtained from light-scattering experiments at several ionic strengths and degrees of protonation.
AB - The acid dissociation constants of long-chain esters of carnitine (β-hydroxy-γ-trimethylammonium-butyrate) above the critical micelle concentration were determined potentiometrically at several concentrations of added KCl. As the degree of protonation β increases the apparent pK values decrease owing to the increased positive charge on the micelle. The difference in pK between the neutral (zwitterionic) micelle and the value at any given β was used to determine the surface potential of the micelle Ψ at that degree of protonation. At each degree of protonation the measured surface potential was related to the surface charge density σ with the aid of the calculations of Loeb, Wiersema, and Overbeek for a spherical impenetrable particle. The surface potentials and surface charge densities of lauryl-, myristyl-, and palmitylcarnitine are nearly identical at a given degree of protonation and ionic strength, and, as expected, increasing the ionic strength produces a decrease in the surface potential. From the partial molal volume of each surfactant in the micelle and the calculated surface charge density it was possible to calculate the aggregation number n of the micelle. Good agreement was found between the calculated values of n and values obtained from light-scattering experiments at several ionic strengths and degrees of protonation.
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U2 - 10.1016/0021-9797(70)90215-8
DO - 10.1016/0021-9797(70)90215-8
M3 - Article
C2 - 5500979
AN - SCOPUS:0014901610
SN - 0021-9797
VL - 34
SP - 525
EP - 533
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
IS - 4
ER -