Using Interfacial Tension Measurements To Study the Kinetics of Ferritin and Sugar Adsorption onto Mercury

Abstract

The kinetics ofholoferritin, apoferritin, glucose, and glycerol adsorption onto a pendant mercury drop in aqueous solutions were investigated by measuring the mercury-water interfacial tension as a function of time. The apparatus used for interfacial tension measurement was constructed in-house and utilized the pendant drop method. To calculate the interfacial tension, the drop profile was digitized and then the experimental points were fitted according to the exact solution of the equation of capillarity by using the least-square optimization principle. In sugar solutions, the mercury-water interfacial tension relaxation and, hence, the adsorption onto the mercury surface were much faster than that in ferritin solutions. The decrease of the drop interfacial tension in the sugar solutions was similar to that in the sugar and ferritin mixed solutions. On the basis of these results, we concluded that sugars adsorb faster than ferritin, and that ferritin molecules attach weakly to the adsorbed sugar layer. Thus, sugars might act as spacers in the sugar and ferritin mixed solutions, protecting ferritin molecules from direct contact with the mercury surface.