ROLE OF HYDRATION AND WATER-STRUCTURE IN BIOLOGICAL AND COLLOIDAL INTERACTIONS

The conventional explanation of why hydrophilic surfaces and macromole cules remain well separated in water is that they experience a monoton ically repulsive hydration force owing to structuring of water molecul es at the surfaces. A consideration of recent experimental and theoret ical results suggests an alternative interpretation in which hydration forces are either attractive or oscillatory, and where repulsions hav e a totally different origin. Further experiments are needed to distin guish between these possibilities.