Lipid bilayer molecular transport

Solute transport and partitioning in lipid bilayers molecular dynamics simulations... 

Key words Lipid bilayer - molecular dynamics simulations - computer simulation - permeability - transport... 

In addition to the self-spreading lipid bilayer, it was also found that a lipid mono-layer showed similar spreading behavior on a hydrophobic surface (Figure 13.6) [51]. By fabricating an appropriate hydrophobic surface pattern, the spreading area and direction can be easily controlled. For both the self-spreading bilayer and monolayer, non-biased molecular transportation is an important key concept for the next generation of microfiuidic devices. 

The most intriguing aspect of the self-spreading lipid bilayer is that any molecule in the bilayer can be transported without any external bias. The unique characteristic of the spreading layer offers the chance to manipulate molecules without applying any external biases. This concept leads to a completely non-biased molecular manipulation system in a microfluidic device. For this purpose, the use of nano-space, which occasionally offers the possibility of controlling molecular diffusion dynamics, would be a promising approach. 

At a more molecular level, the influences of the composition of the membrane domains, which are characteristic of a polarized cell, on diffusion are not specifically defined. These compositional effects include the differential distribution of molecular charges in the membrane domains and between the leaflets of the membrane lipid bilayer (Fig. 3). The membrane domains often have physical differences in surface area, especially in the surface area that is accessible for participation in transport. For example, the surface area in some cells is increased by the presence of membrane folds such as microvilli (see Figs. 2 and 6). The membrane domains also have differences in metabolic selectivity and capacity as well as in active transport due to the asymmetrical distribution of receptors and transporters. 

Cholesterol - an essential component of mammalian cells - is important for the fluidity of membranes. With a single hydroxy group, cholesterol is only weakly am-phipathic. This can lead to its specific orientation within the phospholipid structure. Its influence on membrane fluidity has been studied most extensively in erythrocytes. It was found that increasing the cholesterol content restricts molecular motion in the hydrophobic portion of the membrane lipid bilayer. As the cholesterol content of membranes changes with age, this may affect drug transport and hence drug treatment. In lipid bilayers, there is an upper limit to the amount of cholesterol that can be taken up. The solubility limit has been determined by X-ray diffraction and is... 

Some of these low molecular mass permeation enhancers act as surfactants/ detergents to increase the transcelluar transport of more lipophilic drugs by disrupting the structure of the lipid bilayer and rendering the cell membrane... 

Supported bilayers represent biomimetic layers which can be supported on a range of materials and adapted for the study of biointeractions (protein-protein, lipid-lipid) including molecular recognition, ion-channel transport and intramembrane interactions. This interface type can be separated into the so-called SLBs (supported lipid bilayers), HBMs (hybrid bilayer membranes) and t-BLMs (tethered bilayer membranes). 

---