Analysis of interactions between cinnamycin and biomimetic membranes

Binding Behavior between Transforming-Growth-Factor-Beta1 and Its Receptor Reconstituted in Biomimetic Membranes

Transforming growth factor β1 (TGF-β1) is critical to cell differentiation, proliferation, and apoptosis. It is important to understand the binding affinity between TGF-β1 and its receptors. In this study, their binding force was measured using an atomic force microscope. Significant adhesion was induced by the interaction between the TGF-β1 immobilized on the tip and its receptor reconstituted in the bilayer. Rupture and adhesive failure occurred at a specific force around 0.4~0.5 nN. The relationship of the force to loading rate was used to estimate the displacement where the rupture occurred. The binding was also monitored in real time with surface plasmon resonance (SPR) and interpreted with kinetics to acquire the rate constant. Using the Langmuir adsorption, the SPR data were analyzed to estimate equilibrium and association constants to be approximately 10⁷ M^-1 and 10⁶ M^-1 s^-1. These results indicated that the natural release of the binding seldom occurred. Furthermore, the degree of binding dissociation, confirmed by the rupture interpretation, supported that the reverse of the binding hardly happened.

Kinetic and thermodynamic studies of cinnamycin specific-adsorption on PE-Included-Membranes using surface plasmon resonance

The binding of the cinnamycin on the biomimetic membrane was studied with respect to time using the surface plasmon resonance(SPR). The membrane was composed of the inner layer tethered on the gold surface and the outer layer formed on the inner layer, which was at the desired ratio of dioleoylphosphatidylethanolamine(DOPE) to dioleoylphosphatidyl- choline(DOPC). On the bilayer, the cinnamycin solution was injected and showed different behavior of the binding with respect to time up on its concentration. For kinetic analysis, the behavior was converted to the coverage fraction with respect to time, which was ratio to the saturated response of 5 μM cinnamycin solution. The fraction change with respect to time was function of the available-site, which was eventually the subtraction of the fraction from one. With the fitting of the first order of the available site, the rate constant was acquired into 6∼7 × 10^-3 s^-1. Furthermore, the reciprocals of the fraction and the concentration were fitted with the Langmuir adsorption isotherm. From the fitting, the equilibrium constant was between 1 × 10⁷ and 5 × 10⁷ M^-1.