Non-lamellar phase

Seddon, J. M. (1990). Structure of the inverted hexagonal (HII) phase, and non-lamellar phase transitions of lipids, Biochim. Biophys. Acta, 1031, 1-69. 

As evident from Fig. 11, where different symbols are used to distinguish TE data for lamellar (filled symbols) and non-lamellar phases (open symbols), DL/DOPC-DNA complexes in the Lo,c phase closely follow the universal behavior. These are MVLG2/DOPC-DNA complexes at all DL and DNA complexes of the other DLs at low DL. In contrast, TE of the H c phase and the new distorted hexagonal and DNA bundle phases is not only high but independent of lamellar phases therefore coincides with the deviation from the universal TE curve, suggesting a different mechanism of action for the different structures of DNA complexes. 

As stated, biological membranes are normally arranged as bilayers. It has, however, been observed that some lipid components of biological membranes spontaneously form non-lamellar phases, including the inverted hexagonal form (Figure 1.9) and cubic phases [101]. The tendency to form such non-lamellar phases is influenced by the type of phospholipid as well as by inserted proteins and peptides. An example of this is the formation of non-lamellar inverted phases by the polypeptide antibiotic Nisin in unsaturated phosphatidylethanolamines [102]. Non-lamellar inverted phase formation can affect the stability of membranes, pore formation, and fusion processes. So-called lipid polymorphism and protein-lipid interactions have been discussed in detail by Epand [103]. 

Kinnunen PKJ. On the molecular-level mechanisms of peripheral protein-membrane interactions induced by lipids forming inverted non-lamellar phases. Chem. Phys. Lipids 1996 81 151-166. 

Afonin, S., Frey, A., Bayerl, S., et al. (2006) The cell-penetrating peptide TAT(48-60) induces a non-lamellar phase in DMPC membranes. Chemphyschem, 7, 2134—2142. 

Epand RM. Lipid polymorphism and protein-lipid interactions. Biochim Biophys Acta 1998 1376 353-368. Gawrisch K, Holte LL. NMR investigations of non-lamellar phase promoters in the lamellar phase state. 

In certain phospholipid membranes that contain unsaturated acyl chains, the typical lamellar liquid crystalline phase converts to a micellar non-lamellar phase upon heating [14]. Such a thermally induced transition involves a major structural rearrangement. Temperature studies of the infrared spectra of phospholipids provide a sensitive means of studying such transitions in lipids. Figure 7.2 shows the temperature-dependence of the wavenumber of the symmetric CH2 stretching... 

Among the inverted type non-lamellar phases, various studies have been reported on the formation of bicontinuous cubic (V2) phases, the hexagonal (H2) phase, and the discontinuous cubic (I2) phase of the symmetry Fd3m [81, 88, 89],... 

Monolinolien (MLO) is among the surfactant-like lipids with propensity to form inverted type non-lamellar phases. The binary MLO-water phase diagram is shown in Figure 1 [83]. 

---