Lamellar phase refers generally to packing of

polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates * Polar climate, the c ...

-headed long chain nonpolar-tail

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...

s in an environment of bulk polar liquid, as sheets of bilayers separated by bulk liquid. In

biophysics Biophysics is an interdisciplinary science that applies approaches and methods traditionally used in physics to study biological phenomena. Biophysics covers all scales of biological organization, from molecular to organismic and populations. ...

, polar lipids (mostly,

phospholipids Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...

, and rarely,

glycolipids Glycolipids are lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the connec ...

) pack as a

liquid crystal Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way. T ...

line

bilayer A bilayer is a double layer of closely packed atoms or molecules. The properties of bilayers are often studied in condensed matter physics, particularly in the context of semiconductor devices, where two distinct materials are united to form jun ...

, with

hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, th ...

fatty

acyl In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an alkyl group (). In organic chemistry, the acyl group (IUPAC n ...

long chains directed inwardly and polar headgroups of

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

s aligned on the outside in contact with water, as a 2-dimensional flat sheet surface. Under

transmission electron microscope Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a gr ...

(TEM), after staining with polar headgroup reactive chemical

osmium tetroxide Osmium tetroxide (also osmium(VIII) oxide) is the chemical compound with the formula OsO4. The compound is noteworthy for its many uses, despite its toxicity and the rarity of osmium. It also has a number of unusual properties, one being that the ...

, lamellar lipid phase appears as two thin parallel dark staining lines/sheets, constituted by aligned polar headgroups of lipids. 'Sandwiched' between these two parallel lines, there exists one thicker line/sheet of non-staining closely packed layer of long lipid fatty acyl chains. This TEM-appearance became famous as Robertson's unit membrane - the basis of all

biological membranes A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the ce ...

, and structure of

lipid bilayer The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of almost all organisms and many vir ...

unilamellar liposome A unilamellar liposome is a spherical liposome, a vesicle, bounded by a single bilayer of an amphiphilic lipid or a mixture of such lipids, containing aqueous solution inside the chamber. Unilamellar liposomes are used to study biological systems a ...

s. In multilamellar

liposomes A liposome is a small artificial Vesicle (biology and chemistry), vesicle, spherical in shape, having at least one lipid bilayer. Due to their hydrophobicity and/or hydrophilicity, biocompatibility, particle size and many other properties, lipo ...

, many such lipid bilayer sheets are layered concentrically with water layers in between. In lamellar lipid bilayers, polar headgroups of lipids align together at the interface of water and hydrophobic

fatty-acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...

chains align parallel to one another 'hiding away' from water. The lipid head groups are somewhat more 'tightly' packed than relatively 'fluid' hydrocarbon fatty acyl long chains. The lamellar lipid bilayer organization, thus reveals a 'flexibility gradient' of increasing freedom of motions from near the head-groups towards the terminal fatty-acyl chain methyl groups. Existence of such a dynamic organization of lamellar phase in liposomes as well as biological membranes can be confirmed by

spin label A spin label (SL) is an organic molecule which possesses an unpaired electron, usually on a nitrogen atom, and the ability to bind to another molecule. Spin labels are normally used as tools for probing proteins or biological membrane-local dynami ...

electron paramagnetic resonance Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a method for studying materials that have unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but the spin ...

and high resolution

nuclear magnetic resonance Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...

spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

studies of biological membranes and liposomes. In 'soft matter science', where physics and chemistry meet biological science, a bilayer lamellar phase has been recently created from fluorinated silica, and it has been projected for use as a shear-thinning

lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...

.Pottage M J, Kasuma T, Grillo I, Gravey C J, Stickland A D and Tabor R F (2014
Fluorinated lamellar phases: Structural characterization and use as templates for highly ordered silica materials
''Soft Matter'', vol. 10 (No. 27), pp. 4902-4912.

References

External links

Bilayer formation through molecular self-assembly - YouTubeCell Membrane - The Lipid Bilayer - YouTube
Liquid crystals Membrane biology Surfactants Colloidal chemistry Biophysics {{biophysics-stub

See also

References

External links