INTERACTION FORCES BETWEEN BIOLOGICAL AND OTHER POLAR ENTITIES IN WATER - HOW MANY DIFFERENT PRIMARY FORCES ARE THERE

Whilst mention of at least 17 different varieties of non-covalent interactions in polar media can be encountered in the recent literature, it can be shown that most of these are not themselves separate primary physical-chemical forces, but secondary manifestations of one or several such primary forces. The underlying primary forces that play a role in aspecific or specific non-covalent interactions between colloidal entities in aqueous media are limited to: Lifshitz-van der Waals forces, electrostatic forces, hydrogen-bonding interactions (or more generally, polar, or Lewis acid-base interactions) and Brownian motion-induced interactions. In some instances one must, in addition, deal with repulsive forces between free or attached macromolecules that become enhanced by chain elasticity phenomena, which are, however, not easily quantifiable.