Energetics of cell-cell and cell-biopolymer interactions.

The energy vs distance balance of cell suspensions (in the presence and in the absence of extracellular biopolymer solutions) is studied, not only in the light of the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory (which considered just the electrostatic (EL) and Lifshitz-van der Waals (LW) interactions), but also by taking electron-acceptor/electron-donor, or Lewis acid-base (AB) and osmotic (OS) interactions into account. Since cell surfaces, as well as many biopolymers tend to have strong monopolar electron-donor properties, they are able to engage in a strong mutual AB repulsion when immersed in a polar liquid such as water. The effects of that repulsion have been observed earlier in the guise of hydration pressure. The AB repulsion is, at close range, typically one or two orders of magnitude stronger than the EL repulsion, but its rate of decay is much steeper. In most cases, AB interactions are quantitatively the dominant factor in cell stability (when repulsive) and in "hydrophobic interactions" (when attractive). OS interactions exerted by extracellularly dissolved biopolymers are weak, but their rate of decay is very gradual, so OS repulsions engendered by biopolymer solutions may be of importance in certain long-range interactions. OS interactions exerted by biopolymers attached to cells or particles (e.g., by glycocalix glycoproteins), are very short-ranged and usually are negligibly small in comparison with the other interaction forces, in aqueous media.