Liquid Crystalline Lipids

J. Forbes, C. Husted and E. Oldfield, High-field, high-resolution magic-angle samplespinning nuclear magnetic resonance spectroscopic studies of gel and liquid crystalline lipid bilayers and the effects of cholesterol, J. Am. Chem. Soc., 1988, 110, 1059-1065. 

Koynova R, MacDonald RC (2004) Columnar DNA superlattices in lamellar oethylpho-sphatidylcholine lipoplexes mechanism of the gel-liquid crystalline lipid phase transition. Nano Lett 4 1475-1479... 

Liquid Crystalline Lipid/Water Phases with Cubic Symmetry. 36... 

FIGURE 4.2 Schematic illustration of 2 x 2 x 2 unit cells of a lipid/water phase with gyroid cubic symmetry. In reversed bicontinuous cubic phases the lipid bilayer membrane separates two intertwined water-filled subvolumes resembling 3D arrays of interconnected tunnels. Black box (right) represents an enlargement of a part of the folded liquid crystalline lipid bilayer membrane structure. 

The surfactant association structures have a long history of research ranging from the McBaln introduction of the aqueous micellar concept(1.) over the interpretation of mlcelllzatlon as a critical phenomenon — — to the analysis of the structure of lyotropic liquid crystals(A) and the comprehensive picture of the phase relations in water/surfactant/amphlphile systems.These studies have emphasized the relation between the association structures in isotropic liquid solutions and the liquid crystalline phases. Parallel extensive investigations in crystalline/ liquid crystalline lipid structureshave provided important insight in the mechanisms of the associations. 

Linear Dichroism. A linear dichroism study of the orientation of j8-carotene molecules in lamellar liquid-crystalline lipid systems has been reported/ Linear dichroic spectra of the cross-conjugated carotenals renierapurpurin-20-al (169), 20-(2,3,4-trimethylbenzal)renierapurpurin (170), and 8, 8 -diapocarotene-8,20,8 -trial (171) have been recorded/ The results support the assignment of the 13 -cis configuration to (169) and (170). 

Figure 11. NMR spectra (46.1 MHz) of the plasma membranes of Achole-plasma laidlawii enriched in myristic acid labeled at the terminal methyl group (C-14 0-w s 90%), at the indicated temperatures. The numbers to the right of each spectrum are the fractions of liquid-crystalline lipid calculated by the moment analysis of Ref. 27. (Unpublished data of H. C. Jarrell, R. Deslauriers, and...

A. Angelova, B. Angelov, R. Mutafchieva, S. Leieur, P. Couvreur, Self-assembled multicompartment liquid crystalline lipid carrier for protein, peptide, and nucleic acid drug delivery. Acc. Chem. Res. 44, 147-156 (2011)... 

Shear of a liquid-crystalline lipid phase which is in equilibrium with a water phase can result in exposure of hydrocarbon chains to water which results in a strong tendency to fuse with other bilayers with exposed hydrocarbon chains. The formation of liposomes, discussed in the next paragraph, is a consequence of such rupture and fusion behaviour. Recently, the first experimental measurements of the force behind such adhesion, the hydrophobic force, were reported (Israelachvili and Paskey, 1982). It was found to be a long-range force with the same range of existence as the van der Waals interaction and shows an exponential fall-off with a decay length of 10 A. 

Liquid-crystalline lipid-water phases can under certain conditions incorporate proteins. On the basis of studies of liquid-crystalline phases in various lipid-protein-water systems (Gulik-Krzywicki etal.y 1969 Rand and SenGupta, 1972), it was concluded that a prerequisite for the formation of composite liquid-crystalline phases is that the lipid is charged (Rand, 1976). Recently, however, a system with a neutral lipid was examined which appeared to form a lipid-... 

Many membrane functions can be directly related to the physical properties of the liquid-crystalline lipid bilayer. Variations in curvature and area per unit mass and diffusion properties can thus be explained by the liquid-crystal model. Membrane proteins contain hydrophobic segments in an alpha-helical conformation which constitute the anchor in the hydrophobic core of the bilayer. The proteins contain short chains of sugar groups on the outer surface of the plasma membrane and this surface zone is involved in recognition phenomena. A covalent link between the peptide and the oligo-... 

Dry skin, caused by a loss of horny layer, can be cured by formulations containing extracts of lipids from homy layers of humans or animals. Due to loss of water from the lamellar liquid crystalline lipid bilayers of the homy layer, phase transition to crystalline stmctures may occur, causing contraction of the intercellular regions. The dry skin becomes inflexible and inelastic and it may also crack. 

FIGURE 6.24 Examples of SAXS data collected in two different lipid lamellar phases, (a) The gel phase Lp. on a sample of pure DPPC (l,2-dlpalmltoyl-sn-glycero-3-phosphocholine) and (b) in the liquid crystalline lipid phase on a sample of pure DOPE (l,2-dioleoyl-sn-glycero-3-phosphoethanolamine. Both sets of data were collected using a synchrotron x-ray source at Brookhaven National Laboratory. 

T.X. Xiang and B.D. Anderson. Permeability of acetic acid across gel and liquid-crystalline lipid bilayers conforms to free-surface-area theory. Biophys. J., 72 (1997) 223-237. 

Figure 1. A model which relates a change in the fluidity of the membrane lipid phase to a change in the conformation of a tightly-bound protein. On the left is shown a liquid-crystalline lipid phase which will accommodate a relatively large portion of the protein molecule. On the right is represented a gel phase lipid bilayer from which the protein has been partially extruded, thereby exposing hydrophobic residues on the protein to water the protein will thus rearrange its conformation to internalize these hydrophobic residues.

Some important aspects of the mixing behavior of selected systems should be mentioned. Non-ideal mixing is not only found for lipids in the ordered gel phases but also for liquid-crystalline lipids. Gel phase immiscibility and phase diagrams which are of the peritectic or eutectic type are regularly observed when the two lipids in the mixture have differences in chain length of 4 or more CH2-groups or when the gel phase stnictures are different. For instance, lipids that form inter-... 

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