The suppression of hemolysis induced with 1.0 mM dodecyltrimethylammonium bromide (DTAB) or 1.6 mM 3-(dimethyldodecylammonio)-1-propanesulfonate (DDAPS) by R-, -, and γ-cyclodextrins (CyDs) is determined as a function of CyD concentration at 310 K, and is correlated with the surface tension values of their solutions. These surface tension data allow us to estimate the 1:1, 1:2, and 2:1 binding constants of DTAB or DDAPS with these CyDs. The 2:1 binding constants of DTAB and DDAPS with γ-CyD are larger than their 1:1 binding constants. This cooperative binding of DTAB and DDAPS to γ-CyD is ascribed to the fact that the γ-CyD cavity has an adequate space to accommodate two alkyl chains. Both the capabilities of CyDs for hemolysis suppression and surface tension elevation are in the order R-CyD ≈ -CyD > γ-CyD for 1.0 mM DTAB and 1.6 mM DDAPS. The suppression of DTAB-or DDAPS-induced hemolysis for all the CyDs can be quantitatively predicted from the observed surface tension data, regardless of the kind and concentration of CyD. All the CyDs can bind the surfactants more strongly than phospholipid and cholesterol in the erythrocyte membrane.

The self-association behavior of propantheline bromide in a 154 mmol dm -3 sodium bromide solution has been investigated by frontal chromatography on two Sephadex columns and by the surface tension method. Analysis of centroid volume data by asymptotic theory yields the monomer concentration of propantheline bromide as a function of its total concentration. Further analysis of the concentration dependence of the monomer concentration by a multiple equilibrium model provides weight-average and number-average aggregation numbers. The aggregates of propantheline bromide are small and are formed in a stepwise manner without a cmc. Stepwise aggregation constants for propantheline bromide are estimated and are used to predict the aggregate size distribution. Derivative chromatograms support the above results based on the centroid volume data. For instance, the shape of the derivative chromatogram of propantheline bromide at the trailing boundary is closer to that of penicillin V than to that of the surfactant, suggesting that propantheline bromide self-associates in a nonmicellar mode. The dimerization constant of propantheline bromide estimated from the trailing peak volume is close to that obtained from the centroid volume. The shape of the frontal chromatogram is almost independent of the size of the column. This fact indicates that our chromatographic method for investigating the self-association behavior is reliable. The surface tension of the propantheline bromide solution has a transition, albeit diffuse, when plotted against the logarithm of the total concentration and decreases gradually with increasing concentration above this transition. A reasonable molecular area of propantheline bromide on the aqueous surface is obtained by using the monomer concentration, determined by the chromatographic data, in the Gibbs adsorption equation.

The aggregation patterns of sodium taurocholate (TC) and taurodeoxycholate (TDC) in an isotonic sodium chloride solution at 298.2 K are investigated by frontal derivative chromatography on Sephadex G-10 columns and are quantitatively analyzed on the basis of several aggregation models. The aggregation parameters are best fitted to the observed centroid volume data. The derivative chromatogram of TC at 6.006 mM simulated on the basis of a stepwise aggregation model is in excellent agreement with the observed one, whereas the simulation on the basis of the pentamerization model remarkably differs in shape from the observed one. The derivative chromatograms of TDC at 1.500 and 2.003 mM simulated on the basis of another stepwise aggregation model are closer to the observed ones than those of the Bottari-Festa model. Thus, TC and TDC form their dimers and polydisperse micelles. These conclusions are supported by the fitness to the centroid volume data. In light of the present results and current reports, the structure and counterion binding of bile salt micelles are discussed.