The extended model of Traüble –Haines-Liebowitz. Cholesterol inhibits the water permeability of phospholipid membranes reducing it in nearly one order of magnitude at 1:4 cholesterol:phospholipid ratio. This is concomitant with a reduction in the lateral mobility of the lipids. According to the Haines-Liebowitz-Traüble model, permeability is connected to lateral diffusion [48]. In FTIR spectroscopy, there is a reduction of the value indicating that the connected populations of CH2 increases with the cholesterol ratio, which is totally compatible with the water permeability decrease via the reduction of kinks [44]. Contribution of the interphase. Traüble´s proposal was developed further to understand the mechanism of water permeation in lipid bilayers by Haines and Liebovitz [48]. This model proposes that the generation of kinks in the lipid matrix is due to changes in the conformational state of the lipid head groups. In other words, the membrane is considered as a phase that is sensitive to the presence of solutes in the adjacent aqueous phase. Headgroup lateral movement generates kinks or vacants at …show more content…
In order to interpret it in terms of physical chemical process, the mechanism of interaction and the kind of adsorption process should be analyzed. To proceed further an updated of the membrane regions is required in which the properties of lipid membranes depends on water organization as part of the structure. In consequence, its thermodynamic properties must be redefined. The updated model is described in Figure 6A. The regions of 1 nm thick at each side of the bilayer, denoted as an excluded volume for solutes in the previous session, contain around 18-20 water molecules per lipid in phosphatidylcholines [50,51]. The presence of those interphases describes the membrane as a composite element consisting of the lipid leaflets and the regions of hydrated polar head groups at each