ABSTRACT
Water is the most abundant luid on earth and is indispensable for life. More
than 60% of the volume of living cells is occupied by water, and the loss of
10-20% of its volume causes cell death. In cells, hydrophilic and hydrophobic
effects are of prime importance. These effects are related to the solvent
properties of water and to the fact that some compounds are more or less
soluble in water. The solvent abilities of water arise primarily from the two
properties: its tendency to form hydrogen bonds (very short characteristic
life time, from 10-13 to 10-12 s) and its dipolar character [1]. Water has a high
dielectric constant (ε ≈ 80), which results from its dipolar character. Amphipathic molecules exhibit both hydrophilic and hydrophobic
properties simultaneously. When one attempts to dissolve them in water,
amphipathic substances form peculiar structures. Possible structures are a
monolayer on the water surface, a micelle and a bilayer vesicle, with water
both inside and outside. Examples of other structures that impose spatial
restrictions on water molecules include polymer gels and microemulsions.
