Structural Effects of Urea and Tmo on Lipid Bilayers

Abstract

Lipid bilayers can display a wide range of morphologies and are simple models for the cell membrane, that not only defines the cell limits but also provides a matrix for anchoring a variety of substances, e.g, membrane proteins, glycolipids, etc., that play an essential role in the cell. Recently, we have been studying the structural effects of synthetic quinones on lipid model membranes, in order to investigate their contribution to morphologies possibly involved in the electron transfer process. Summarizing, we can say that the insertion of these synthetic additives lower the temperature of the structural phase transitions comparative to pure lipids and in many cases induce the formation of cubic phases at low temperatures, e.g. 30°C, which corresponds to an increase of the lipid matrix surface curvature. The scattering patterns of the cubic phases are clearly identifiable, despite their intrinsic low resolution. In some cases micellar cubic phases were observed. In this study we shifted our attention to the influence of small molecules such as urea and TMAO. It is accepted that they have antagonistic effects on the fluidity of lipid membranes. In red blood cells, urea slightly increases the gel-phase domains, but this effect is counteracted by TMAO. We intended to determine how these organic solutes affect the structure of a lipid membrane and determine their contribution to the possible curvature induced on them. We could see a change on the temperature of phase transitions and the formation of induced phases or structures.