Membrane lateral organization

Soderlund T, Jutila A, Kinnunen PKJ. Binding of adriamycin to liposomes as a probe for membrane lateral organization. Biophys. J. 1999 76 896-907. 

There are other ways in which the lateral organization (and asymmetry) of lipids in biological membranes can be altered. Eor example, cholesterol can intercalate between the phospholipid fatty acid chains, its polar hydroxyl group associated with the polar head groups. In this manner, patches of cholesterol and phospholipids can form in an otherwise homogeneous sea of pure phospholipid. This lateral asymmetry can in turn affect the function of membrane proteins and enzymes. The lateral distribution of lipids in a membrane can also be affected by proteins in the membrane. Certain integral membrane proteins prefer associations with specific lipids. Proteins may select unsaturated lipid chains over saturated chains or may prefer a specific head group over others. 

Recently, due to increased interest in membrane raft domains, extensive attention has been paid to the cholesterol-dependent liquid-ordered phase in the membrane (Subczynski and Kusumi 2003). The pulse EPR spin-labeling DOT method detected two coexisting phases in the DMPC/cholesterol membranes the liquid-ordered and the liquid-disordered domains above the phase-transition temperature (Subczynski et al. 2007b). However, using the same method for DMPC/lutein (zeaxanthin) membranes, only the liquid-ordered-like phase was detected above the phase-transition temperature (Widomska, Wisniewska, and Subczynski, unpublished data). No significant differences were found in the effects of lutein and zeaxanthin on the lateral organization of lipid bilayer membranes. We can conclude that lutein and zeaxanthin—macular xanthophylls that parallel cholesterol in its function as a regulator of both membrane fluidity and hydrophobicity—cannot parallel the ability of cholesterol to induce liquid-ordered-disordered phase separation. 

Biological membranes fluidity order parameters lipid-protein interactions translational diffusion site accessibility structural changes membrane potentials complexes and binding energy-linked and light-induced changes effects of additives location of proteins lateral organization and dynamics... 

The structure of biological and model membranes is frequently viewed in the context of the fluid mosaic model [4], Since biological membranes are composed of a mixture of various lipids, proteins, and carbohydrates the supra-structure or lateral organization of the components is not necessarily random. In order to model biological membranes, lipid assemblies of increasing complexity were studied. Extensive investigation of multicomponent monolayers (at the air-water interface) as well as bilayers have been reported. 

Bagatolli LA. To see or not to see lateral organization of biological membranes and fluorescence microscopy. Biochim. Biophys. Acta 2006 1758 1541-1556. 

Determination of the lateral organization of liposomal membranes on scales ranging from 10 to 1000 nm has proved elusive [27-30]. However, indirect and direct... 

C. Leidy, W.F. Wolkers, O.G. Mouritsen, K. Jorgensen, and J.H. Crowe. Lateral organization and domain formation in a two-component lipid membrane system. Biophys.J., 2001, 80, 1819-1828. 

Certainly, more complex lipid systems, such as the three-component "raft"-mixtures may represent more realistic models for biomembrane systems. Their pressure dependent lateral organization and phase behavior has not been studied yet, however. Some data are available on pressure effects on lipid extracts from natural membranes, such as bipolar tetraether liposomes composed of the polar lipid fraction E (PLFE) isolated from the thermoacidophilic archaeon Sulfolobus acidocaldarius. The SAXS data on PLFE multilamellar vesicles also exhibit several temperature dependent lamellar phases, and, in addition, the existence of cubic... 

In this section, we introduce the protein filaments that compose the cytoskeleton and then describe how they support the plasma and nuclear membranes and organize the contents of the cell. Later chapters will deal with the dynamic properties of the cytoskeleton—its assembly and disassembly and its role in cellular movements. 

D. E. Wolf (1988) Probing the Lateral Organization and Dynamics of Membranes. In Spectroscopic Membrane Probes. 

LHCII and several PSII thylakoid proteins are phosphorylated by an ATP dependent protein kinase (1,2), which is under control of the redox state of the PQ pool (3). This protein phosphorylation leads to rearrangements in the lateral organization of the thylakoid membrane... 

Membrane phenomena cover an extremely broad field. Membranes are organized structures especially designed to perform several specific functions. They act as a barrier in living organisms to separate two regions, and they must be able to control the transport of matter. Moreover, alteration in transmembrane potentials can have a profound effect on key physiological processes such as muscle contraction and neuronal activity. In 1875, Gibbs stated the thermodynamic relations that form the basis of membrane equilibria. The theory of ionic membrane equilibrium was developed later by Donnan (1911). From theoretical considerations, Donnan obtained an expression for the electric potential difference, commonly known as the membrane potential between two phases. 

In the last decade, several groups have demonstrated that metal ions can be coordinated to vesicles in a highly selective manner if suitable amphiphilic ligands are embedded in the membrane. In certain cases, coordination of metal ions to vesicles results in the formation of unusual complexes and remarkable changes in the lateral organization of the membrane. Three representative examples are highlighted below. 

K. Jorgensen, O. G. Mouritsen, Phase separation dynamics and lateral organization of two-component lipid membranes, Biophys. J. 95 (1995) 942. 

Pervaporation is a process in which organic solvent water mixture or organic solvent mixture can be separated by partial vaporization through a nonporous permeate selective membrane. In this process liquid feed mixture circulates in contact with the active nonporous side of the membrane while a vacuum is applied on the other side of the membrane. A phase change of membrane-selective permeate takes place in the membrane. The membrane-selective permeate diffuses through the membrane and desorbs on the posterior side of the membrane. Later, it evaporates with the help of a vacuum from the posterior side of the active nonporous membrane. The transport of the permeate through a nonporous permeate-selective membrane is quite complex. This could be explained in three steps, which are as follows ... 

---