Antifluorescyl IgG antibody and Fab binding to two fluorescein-conjugated lipids was measured using the quartz crystal microbalance methodology. By use of the Langmuir-Blodgett technique, the fluorescein lipids, which were diluted to 5% in a L-alpha-dipalmitoyl phosphatidylethanolamine (DPPE) matrix, were deposited directly onto one gold electrode of the quartz crystal. Binding to films containing the fluorescein hapten was significantly enhanced compared to films of the pure DPPE matrix lipid, indicating that binding occurred primarily through a specific interaction. Association constants were 40-300 times less than for binding to haptens free in solution. Binding of IgG to the lipid in which the hydrocarbon chains and the fluorescein hapten were linked via a hydrophilic spacer was approximately 7 times as great as to the lipid containing no spacer. IgG binding to the lipid containing the spacer was increased 1.5-4.4 times compared to Fab binding for the same lipid. Equilibrium binding curves and kinetic measurements are analyzed quantitatively and compared.

No abstract

Specific adsorptions of bitter or odorous substances on a synthetic lipid multibilayer matrix (2C18N+2C1/PSS-) were detected by observing frequency changes of a multibilayer-coated quartz-crystal microbalance (QCM). Partition coefficient (P) and diffusion constants (D) of these substances in the lipid matrix could be obtained quantitatively by using the QCM method. There were good correlations between partition coefficients of various bitter or odor substances to the synthetic multibilayer film on the QCM and the intensity of bitter tastes or olfactory receptions in humans: the stronger the intensity of a bitter substance or odorant, the greater the adsorption on the lipid matrix. This indicates that the lipid-coated QCM acts as a sensitive and selective sensor for bitter taste and odor. Electric responses (changes of membrane potential and membrane resistance) of the 2C18N+2C1/PSS-film occurred consecutively by the adsorption of these substances. The bitter or odor substance showing the stronger intensity induced membrane potential change in lower concentrations. It was found that bitter substances having sterically bulky molecular structures adsorb on the surface of the lipid matrix, and the phase-boundary potential of the membrane is thereby changed. On the contrary, odor substances with relatively small or slender structures can penetrate into the lipid matrix and cause reduction of the membrane resistance (the increase of ion permeability). The selective adsorption behavior of bitter and odor substances by molecular shapes was confirmed by adsorption studies of simple C9-10 hydrophobic alcohols having various molecular structures.

on o=o, the limiting velocity for long columns obtained by the WRL theory. The effect of the column length is expressed by the second factor in eq 8 with the Laplace length as a scaling factor.Acknowledgment. L.G. is indebted to the University of Antwerp (U.I.A.) for a postdoctoral fellowship during the course of this work. We also thank Guido Serrien for help during the preparation of this manuscript.

The absorption behaviors of 13 kinds of surfactant molecules in a lipid matrix were studied by using a synthetic dlmethyldioctadecylammonium poly(styrene-4-sulfonate) (2C18N+-2C1/PSS') microbalance or a naturally Occurring dlpalmttoylphosphatldylethanoiamine (DPPE) multlbilayer filmcoated quartz-crystal microbalance (QCM) In distilled water. The resonance frequency of the lipid-coated QCM decreased linearly with Increasing the mass of substances deposited in the lipid matrix on the QCM, and the partition coefficients (P) and diffusion rate constants (D) were obtained quantitatively.