EFFECT OF INORGANIC-IONS ON CHANGES IN THE ENERGETIC HETEROGENEITY OFTHE CHOLESTEROL SURFACE

The effect of the adsorption on cholesterol of cations H+, Li+, Na+, K +, Ca2+, Mg2+, Ba2+, and Al3+ and anions OH-, Cl-, Br, I-, NO3-, SO42- , and PO43- On the surface energetic heterogeneity was studied. The su rface free energy components, Lifshitz-van der Waals, gamma(s)LW, elec tron acceptor, gamma(s)+, and electron donor, gamma(s)-, were calculat ed from measured contact angles of diiodomethane, water, and formamide . It was found that all the ions increase the surface heterogeneity of cholesterol by increasing the acid-base interactions, and especially the electron donor component. The influence is most probably due to th e presence of ordered water molecules hydrating the ions. The most cha racteristic feature of the ions influence is the existence of a practi cally linear relationship between the electron donor, gamma(s)-, compo nent and the entropy of hydration of the ions. Similarly, a linear rel ationship appears between the work of water adhesion to the surface an d the entropy of hydration. Despite the increased polarity of the chol esterol surface, it still possesses hydrophobic character after adsorp tion of the ions, because even in the case of Al3+ cation (the highest influence), the work of water adhesion is 41 mJ/M2 lower than the wor k of water cohesion, this giving rise to a 64-degrees contact angle of water on the surface.