Long-range interactions between macromolecules in ordered media

The results of theoretical calculations of interactions between macromolecules dissolved in ordered media such as liquid crystals and biological membranes (lipid bilayers) are reviewed. Expressions for the potentials of interactions between macromolecules of different shape incorporated into nematic liquid crystals, thin films, and lipid mono- and bilayers were derived. In addition to exact expressions, simple evaluating formulae are given. The two-dimensional "gas" of macromolecules swimming on the membrane was considered, and the expression of state for this "gas" was derived. It was shown that in the "gas", phase transitions accompanied by the formation of two-dimensional clusters may occur. The estimates of critical density at which these transitions occur are given.