Penetration into bilayer lipid membranes

Ras is strictly localized to the inner side of the plasma membrane. A lipid anchor covalently attached to the C-terminus of Ras penetrates into the lipid bilayer. This membrane anchorage is essential for the biological activity of Ras. Hence, the inhibition of anchor attachment has become an attractive pharmacological target [ 13]. See Waldmann H, Thutewohl M,Ras-Farnesyltransferase-inhibitors as promising anti-tumor drugs, this volume. 

As mentioned earlier, fullerene molecules can destroy the virions, but do not affect living cells. It is possible to suppose that the differences of the structures of virion envelope and cell membrane are the main reason for this phenomenon the outer side of virion envelope is enriched with protein molecules, whereas the outer side of cell membranes is more lipophylic. On the one hand, fullerene molecules can interact with proteins (Belgorodsky et al., 2006), and on the other hand, their penetration into a lipid bilayer does not destroy them (Ikeda et al., 2005 Piotrovsky, 2006). So it is not unlikely that the difference in the structure of outer side is the main driving force of the observed differences in the response of virions and cells in the presence of C60. 

Figure 3 A hydrophobic permeant must negotiate through a complex series of diffu-sional and thermodynamic barriers as it penetrates into a cell. The lipid and protein compositions and charge distribution of the inner and outer leaflets of the membrane lipid bilayer can play limiting roles, particularly at the tight junction. Depending upon the permeant s characteristics, it may remain within the plasma membrane or enter the cytoplasm, possibly in association with cytosolic proteins, and partition into cytoplasmic membranes.

A bilayer formed from complex lipids, largely glycerophospholipids, forms the core structure of biological membranes. This bilayer forms a barrier to penetration of exogenous molecules into the cellular interior. Proteins penetrate into or through this bilayer. 

In addition, some flavonoids can differentially interact with membrane polar surfaces or penetrate into the bilayer, depending on certain characteristics of the reaction milieu. This is the case of quercetin, a flavonoid that at acidic pH is deeply embedded into planar lipid bilayers [Movileanu et al., 2000], while at... 

Langner and S. W. Huie. Iodide penetration into lipid bilayers as a probe of membrane lipid organization. Chem. and Phys. of Lipids 60 127-132 (1991). Chalpin and A. M. Kleinfeld. Interaction of fluorescence quenchers with the n-(9-anthroyloxy) fatty acid membrane probes. Biochim. et Biophys. Acta 73I 465-A14 (1983). 

The central stmctural feature of almost all biological membranes is a continuous and fluid lipid bilayer that serves as the major permeability barrier of the cell or intracellular compartment (1) and as a scaffold for the attachment and organization of other membrane constituents (2, 3). In particular, peripheral membrane proteins are bound to the surface of lipid bilayers primarily by electrostatic and hydrogen-bonding interactions, whereas integral membrane proteins penetrate into, and usually span, the lipid bilayer, and are stabilized by hydrophobic and van der Waal s interactions with the lipid hydrocarbon chains in the interior of the lipid bilayer as well as by polar interactions... 

---