Structural Role of Water in Lipoprotein Systems

Abstract

In a previous communication [1] the author has demonstrated that a water monolayer adsorbed between protein and lipids could account for many properties of biological membranes, including the conduction of electrical energy. Studies on the conductivity of wet protein [2–6] have already led to the conclusion [2] that the absorbed water probably was responsible for this conductivity. On the other hand, Eigen [7] and then Klotz [8] have described a mechanism whereby protons (or electrons) could jump bucket-brigade fashion from one water molecule to another, thus travelling long distances. This mechanism was first advanced [7] to explain the fact that the conductivity of ice is much larger than that of water. However, a close fit of water molecules in an ordered lattice is a perquisite in this mechanism. Thus an ice-like lattice would have to be postulated for the adsorbed water monolayer. It would be also necessary to demonstrate that the parameters of this lattice fit those of proteins and lipids so that both could be linked to the water monolayer by hydrogen bonds. There have been proposed for this lattice, parameters [1] which have been calculated by assuming in the monolayer a symmetrical hexagonal distribution of water molecules linked by 2.77 Å hydrogen bonds.