Phospholipid

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Phospholipid
The left image shows a phospholipid, and the right image shows the chemical makeup.
Phosphatidyl choline is the major component of lecithin. It is also a source for choline in the synthesis of acetylcholine in cholinergic neurons.
Cell membranes consist of phospholipid bilayers

Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Most phospholipids contain a diglyceride, a phosphate group, and a simple organic molecule such as choline; one exception to this rule is sphingomyelin, which is derived from sphingosine instead of glycerol. The first phospholipid identified as such in biological tissues was lecithin, or phosphatidylcholine, in the egg yolk, by Theodore Nicolas Gobley, a French chemist and pharmacist, in 1847. The structure of the phospholipid molecule generally consists of hydrophobic tails and a hydrophilic head. Biological membranes in eukaryotes also contain another class of lipid, sterol, interspersed among the phospholipids and together they provide membrane fluidity and mechanical strength. Purified phospholipids are produced commercially and have found applications in nanotechnology and materials science.[1]

Amphipathic character[edit]

The 'head' is hydrophilic (attracted to water), while the hydrophobic 'tails' are repelled by water and are forced to aggregate. The hydrophilic head contains the negatively charged phosphate group, and glycerol. The hydrophobic tail usually consists of 2 long fatty acid hydrocarbon chains. When placed in water, phospholipids form a variety of structures depending on the specific properties of the phospholipid. These specific properties allow phospholipids to play an important role in the phospholipid bilayer. In biological systems, the phospholipids often occur with other molecules (e.g., proteins, glycolipids, sterols) in a bilayer such as a cell membrane.[2] Lipid bilayers occur when hydrophobic tails line up against one another, forming a membrane of hydrophilic heads on both sides facing the water.

Such movement can be described by the fluid mosaic model, that describes the membrane as a mosaic of lipid molecules that act as a solvent for all the substances and proteins within it, so proteins and lipid molecules are then free to diffuse laterally through the lipid matrix and migrate over the membrane. Sterols contributes to membrane fluidity by hindering the packing together of phospholipids. However, this model has now been superseded, as through the study of lipid polymorphism it is now known that the behaviour of lipids under physiological (and other) conditions is not simple.

Types of phospholipid[edit]

Diacylglyceride structures[edit]

See: Glycerophospholipid

Phosphosphingolipids[edit]

Applications[edit]

Phospholipids have been widely used to prepare liposomal, ethosomal and other nanoformulations of topical, oral and parenteral drugs for differing reasons like improved bio-availability, reduced toxicity and increased penetration. Ethosomal formulation of ketoconazole using Phospholipids showed good entrapment efficiency, stability profile and is a promising option for transdermal delivery with potential for topical application in fungal infections.[3] Liposomes are often composed of phosphatidylcholine-enriched phospholipids and may also contain mixed Phospholipid chains with surfactant properties.

Simulations[edit]

Computational simulations of phospholipids are often performed using molecular dynamics with force fields such as GROMOS, CHARMM, or AMBER.

Characterization[edit]

Phospholipids are optically highly birefringent, i.e. their refractive index is different along their axis as opposed to perpendicular to it. Measurement of birefringence can be achieved using cross polarisers in a microscope to obtain an image of e.g. vesicle walls or using techniques such as dual polarisation interferometry to quantify lipid order or disruption in supported bilayers.

Analysis[edit]

There are no simple methods available for analysis of Phospholipids since the close range of polarity between different phospholipid species makes detection difficult.[4] Oil chemists often use spectroscopy to determine total Phosphorus content and then calculate content of Phospholipids based on molecular weight of expected fatty acid species. Lipidomists use more absolute methods of analysis of with nuclear magnetic resonance spectroscopy (NMR), particularly 31P-NMR,[5][6] while HPLC-ELSD[7] provides relative values.

Phospholipid synthesis[edit]

Phospholipid synthesis occurs in the cytosol adjacent to ER membrane that is studded with proteins that act in synthesis (GPAT and LPAAT acyl transferases, phosphatase and choline phosphotransferase) and allocation (flippase and floppase). Eventually a vesicle will bud off from the ER containing phospholipids destined for the cytoplasmic cellular membrane on its exterior leaflet and phospholipids destined for the exoplasmic cellular membrane on its inner leaflet.[8]

Sources[edit]

Common sources of industrially produced phospholipids are soya, rapeseed, sunflower, chicken eggs, bovine milk, fish eggs etc. Each source has a unique profile of individual phospholipid species and consequently differing applications in food, nutrition, pharmaceuticals, cosmetics and drug delivery.

In signal transduction[edit]

Some types of phospholipid can be split to produce products that function as second messengers in signal transduction. Examples include phosphatidylinositol (4,5)-bisphosphate (PIP2), that can be split by the enzyme Phospholipase C into inositol triphosphate (IP3) and diacylglycerol (DAG), which both carry out the functions of the Gq type of G protein in response to various stimuli and intervene in various processes from long term depression in neurons[9] to leukocyte signal pathways started by chemokine receptors.[10]

Phospholipids also intervene in prostaglandin signal pathways as the raw material used by lipase enzymes to produce the prostaglandin precursors. In plants they serve as the raw material to produce Jasmonic acid, a plant hormone similar in structure to prostaglandins that mediates defensive responses against pathogens.

Food technology[edit]

Phospholipids can act as an emulsifier, enabling oils to form a colloid with water. Phospholipids are one of the components of lecithin which is found in egg-yolks, as well as being extracted from soy beans, and is used as a food additive in many products, and can be purchased as a dietary supplement. Lysolecithins are typically used for WO emulsions like margarine due to their higher HLB ratio.

Phospholipid derivatives[edit]

See table below for an extensive list.

Abbreviations used and chemical information of glycerophospholipids[edit]

AbbreviationCASNameType
DDPC3436-44-01,2-Didecanoyl-sn-glycero-3-phosphocholinePhosphatidylcholine
DEPA-NA80724-31-81,2-Dierucoyl-sn-glycero-3-phosphate (Sodium Salt)Phosphatidic acid
DEPC56649-39-91,2-Dierucoyl-sn-glycero-3-phosphocholinePhosphatidylcholine
DEPE988-07-21,2-Dierucoyl-sn-glycero-3-phosphoethanolaminePhosphatidylethanolamine
DEPG-NA1,2-Dierucoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt)Phosphatidylglycerol
DLOPC998-06-11,2-Dilinoleoyl-sn-glycero-3-phosphocholinePhosphatidylcholine
DLPA-NA1,2-Dilauroyl-sn-glycero-3-phosphate (Sodium Salt)Phosphatidic acid
DLPC18194-25-71,2-Dilauroyl-sn-glycero-3-phosphocholinePhosphatidylcholine
DLPE1,2-Dilauroyl-sn-glycero-3-phosphoethanolaminePhosphatidylethanolamine
DLPG-NA1,2-Dilauroyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt)Phosphatidylglycerol
DLPG-NH41,2-Dilauroyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Ammonium Salt)Phosphatidylglycerol
DLPS-NA1,2-Dilauroyl-sn-glycero-3-phosphoserine (Sodium Salt)Phosphatidylserine
DMPA-NA80724-31,2-Dimyristoyl-sn-glycero-3-phosphate (Sodium Salt)Phosphatidic acid
DMPC18194-24-61,2-Dimyristoyl-sn-glycero-3-phosphocholinePhosphatidylcholine
DMPE988-07-21,2-Dimyristoyl-sn-glycero-3-phosphoethanolaminePhosphatidylethanolamine
DMPG-NA67232-80-81,2-Dimyristoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt)Phosphatidylglycerol
DMPG-NH41,2-Dimyristoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Ammonium Salt)Phosphatidylglycerol
DMPG-NH4/NA1,2-Dimyristoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium/Ammonium Salt)Phosphatidylglycerol
DMPS-NA1,2-Dimyristoyl-sn-glycero-3-phosphoserine (Sodium Salt)Phosphatidylserine
DOPA-NA1,2-Dioleoyl-sn-glycero-3-phosphate (Sodium Salt)Phosphatidic acid
DOPC4235-95-41,2-Dioleoyl-sn-glycero-3-phosphocholinePhosphatidylcholine
DOPE4004-5-1-1,2-Dioleoyl-sn-glycero-3-phosphoethanolaminePhosphatidylethanolamine
DOPG-NA62700-69-01,2-Dioleoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt)Phosphatidylglycerol
DOPS-NA70614-14-11,2-Dioleoyl-sn-glycero-3-phosphoserine (Sodium Salt)Phosphatidylserine
DPPA-NA71065-87-71,2-Dipalmitoyl-sn-glycero-3-phosphate (Sodium Salt)Phosphatidic acid
DPPC63-89-81,2-Dipalmitoyl-sn-glycero-3-phosphocholinePhosphatidylcholine
DPPE923-61-51,2-Dipalmitoyl-sn-glycero-3-phosphoethanolaminePhosphatidylethanolamine
DPPG-NA67232-81-91,2-Dipalmitoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt)Phosphatidylglycerol
DPPG-NH473548-70-61,2-Dipalmitoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Ammonium Salt)Phosphatidylglycerol
DPPS-NA1,2-Dipalmitoyl-sn-glycero-3-phosphoserine (Sodium Salt)Phosphatidylserine
DSPA-NA108321-18-21,2-Distearoyl-sn-glycero-3-phosphate (Sodium Salt)Phosphatidic acid
DSPC816-94-41,2-Distearoyl-sn-glycero-3-phosphocholinePhosphatidylcholine
DSPE1069-79-01,2-Distearoyl-sn-glycero-3-phosphoethanolaminePhosphatidylethanolamine
DSPG-NA67232-82-01,2-Distearoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt)Phosphatidylglycerol
DSPG-NH4108347-80-41,2-Distearoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Ammonium Salt)Phosphatidylglycerol
DSPS-NA1,2-Distearoyl-sn-glycero-3-phosphoserine (Sodium Salt)Phosphatidylserine
Egg Sphingomyelin empty Liposome
EPCEgg-PCPhosphatidylcholine
HEPCHydrogenated Egg PCPhosphatidylcholine
HSPCHydrogenated Soy PCPhosphatidylcholine
LYSOPC MYRISTIC18194-24-61-Myristoyl-sn-glycero-3-phosphocholineLysophosphatidylcholine
LYSOPC PALMITIC17364-16-81-Palmitoyl-sn-glycero-3-phosphocholineLysophosphatidylcholine
LYSOPC STEARIC19420-57-61-Stearoyl-sn-glycero-3-phosphocholineLysophosphatidylcholine
Milk Sphingomyelin MPPC1-Myristoyl-2-palmitoyl-sn-glycero 3-phosphocholinePhosphatidylcholine
MSPC1-Myristoyl-2-stearoyl-sn-glycero-3–phosphocholinePhosphatidylcholine
PMPC1-Palmitoyl-2-myristoyl-sn-glycero-3–phosphocholinePhosphatidylcholine
POPC26853-31-61-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholinePhosphatidylcholine
POPE1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolaminePhosphatidylethanolamine
POPG-NA81490-05-31-Palmitoyl-2-oleoyl-sn-glycero-3[Phospho-rac-(1-glycerol)...] (Sodium Salt)Phosphatidylglycerol
PSPC1-Palmitoyl-2-stearoyl-sn-glycero-3–phosphocholinePhosphatidylcholine
SMPC1-Stearoyl-2-myristoyl-sn-glycero-3–phosphocholinePhosphatidylcholine
SOPC1-Stearoyl-2-oleoyl-sn-glycero-3-phosphocholinePhosphatidylcholine
SPPC1-Stearoyl-2-palmitoyl-sn-glycero-3-phosphocholinePhosphatidylcholine

See also[edit]

References[edit]

  1. ^ Mashaghi S., Jadidi T., Koenderink G., Mashaghi A. (2013). "Lipid Nanotechnology". Int. J. Mol. Sci. 2013 (14): 4242–4282. doi:10.3390/ijms14024242. 
  2. ^ Campbell, Neil A.; Brad Williamson; Robin J. Heyden (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 0-13-250882-6.  [page needed]
  3. ^ Ketoconazole Encapsulated Liposome and Ethosome: GUNJAN TIWARI
  4. ^ HPLC SEPARATION of PHOSPHOLIPIDS - W.W. Christie
  5. ^ P. Meneses and T. Glonek (1988). "High resolution 31P NMR of extracted phospholipids". The Journal of Lipid Research 29 (5): 679–689. PMID 3411242. 
  6. ^ Furse, Samuel; Liddell, Susan; Ortori, Catharine A.; Williams, Huw; Neylon, D. Cameron; Scott, David J.; Barrett, David A.; Gray, David A. (2013). "The lipidome and proteome of oil bodies from Helianthus annuus (common sunflower)". Journal of Chemical Biology 6 (2): 63–76. doi:10.1007/s12154-012-0090-1. PMC 3606697. PMID 23532185. 
  7. ^ T.L. Mounts, A.M. Nash (1990). "HPLC analysis of phospholipids in crude oil for evaluation of soybean deterioration". Journal of the American Oil Chemists' Society 67 (11): 757–760. doi:10.1007/BF02540486. 
  8. ^ Lodish, Harvey; Berk, Krieger, Kaiser, Scott, Bretsher, Ploegh, Matsuaira (2008). Molecular Cell Biology. W.H. Freeman and Company. ISBN 0-7167-7601-4.  [page needed]
  9. ^ Choi, S.-Y.; Chang, J; Jiang, B; Seol, GH; Min, SS; Han, JS; Shin, HS; Gallagher, M; Kirkwood, A (2005). "Multiple Receptors Coupled to Phospholipase C Gate Long-Term Depression in Visual Cortex". Journal of Neuroscience 25 (49): 11433–43. doi:10.1523/JNEUROSCI.4084-05.2005. PMID 16339037. 
  10. ^ Cronshaw, D. G.; Kouroumalis, A; Parry, R; Webb, A; Brown, Z; Ward, SG (2006). "Evidence that phospholipase C-dependent, calcium-independent mechanisms are required for directional migration of T lymphocytes in response to the CCR4 ligands CCL17 and CCL22". Journal of Leukocyte Biology 79 (6): 1369–80. doi:10.1189/jlb.0106035. PMID 16614259.