Phospholipid
The U indicates the uncharged hydrophobic portion of the molecule, highlighted in blue.
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. It is usually found with cholesterol molecules which are found in-between the spaces of the phospholipid.
Amphipathic character
The 'head' is hydrophilic (attracted to water), while the hydrophobic 'tails' are repelled by water and are forced to aggregate. The hydrophillic head contains the negatively charged phosphate group, and may contain other polar groups. The hydrophobic tail usually consists of 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, cholesterol) in a bilayer such as a cell membrane.[1] Lipid bilayers occur when hydrophobic tails line up against one another, forming a membrane 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. Cholesterol 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 However, this model has now been superseded, as through the study of lipid polymorphism it is now known that the behaviour of lipids under physiological (and other) conditions is not simple.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
Diacylglyceride structures
- See: Glycerophospholipid
- Phosphatidic acid (phosphatidate) (PA)
- Phosphatidylethanolamine (cephalin) (PE)
- Phosphatidylcholine (lecithin) (PC)
- Phosphatidylserine (PS)
- Phosphoinositides:
- Phosphatidylinositol (PI)
- Phosphatidylinositol phosphate (PIP)
- Phosphatidylinositol bisphosphate (PIP2) and
- Phosphatidylinositol triphosphate (PIP3).
Phosphosphingolipids
- Ceramide phosphorylcholine (Sphingomyelin) (SPH)
- Ceramide phosphorylethanolamine (Sphingomyelin) (Cer-PE)
- Ceramide phosphorylglycerol
Simulations
Computational simulations of phospholipids are often performed using molecular dynamics with force fields such as GROMOS, CHARMM, or AMBER.
Characterization
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.
Phospholipid synthesis
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.[2]
In signal transduction
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[3] to leukocyte signal pathways started by chemokine receptors.[4]
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
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.
Phospholipid derivatives
- See table below for an extensive list.
- Natural phospholipid derivates:
- egg PC, egg PG, soy PC, hydrogenated soy PC, sphingomyelin as natural phospholipids.
- Synthetic phospholipid derivates:
- Phosphatidic acid (DMPA, DPPA, DSPA)
- Phosphatidylcholine (DDPC, DLPC, DMPC, DPPC, DSPC, DOPC, POPC, DEPC)
- Phosphatidylglycerol (DMPG, DPPG, DSPG, POPG)
- Phosphatidylethanolamine (DMPE, DPPE, DSPE DOPE)
- Phosphatidylserine (DOPS)
- PEG phospholipid (mPEG-phospholipid, polyglycerin-phospholipid, funcitionalized-phospholipid, terminal activated-phospholipid)
Abbreviations used and chemical information of glycerophospholipids
| Abbreviation | CAS | Name | Type |
|---|---|---|---|
| DDPC | 3436-44-0 | 1,2-Didecanoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
| DEPA-NA | 80724-31-8 | 1,2-Dierucoyl-sn-glycero-3-phosphate (Sodium Salt) | Phosphatidic acid |
| DEPC | 56649-39-9 | 1,2-Dierucoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
| DEPE | 988-07-2 | 1,2-Dierucoyl-sn-glycero-3-phosphoethanolamine | Phosphatidylethanolamine |
| DEPG-NA | 1,2-Dierucoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt) | Phosphatidylglycerol | |
| DLOPC | 998-06-1 | 1,2-Dilinoleoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
| DLPA-NA | 1,2-Dilauroyl-sn-glycero-3-phosphate (Sodium Salt) | Phosphatidic acid | |
| DLPC | 18194-25-7 | 1,2-Dilauroyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
| DLPE | 1,2-Dilauroyl-sn-glycero-3-phosphoethanolamine | Phosphatidylethanolamine | |
| DLPG-NA | 1,2-Dilauroyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt) | Phosphatidylglycerol | |
| DLPG-NH4 | 1,2-Dilauroyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Ammonium Salt) | Phosphatidylglycerol | |
| DLPS-NA | 1,2-Dilauroyl-sn-glycero-3-phosphoserine (Sodium Salt) | Phosphatidylserine | |
| DMPA-NA | 80724-3 | 1,2-Dimyristoyl-sn-glycero-3-phosphate (Sodium Salt) | Phosphatidic acid |
| DMPC | 18194-24-6 | 1,2-Dimyristoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
| DMPE | 988-07-2 | 1,2-Dimyristoyl-sn-glycero-3-phosphoethanolamine | Phosphatidylethanolamine |
| DMPG-NA | 67232-80-8 | 1,2-Dimyristoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt) | Phosphatidylglycerol |
| DMPG-NH4 | 1,2-Dimyristoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Ammonium Salt) | Phosphatidylglycerol | |
| DMPG-NH4/NA | 1,2-Dimyristoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium/Ammonium Salt) | Phosphatidylglycerol | |
| DMPS-NA | 1,2-Dimyristoyl-sn-glycero-3-phosphoserine (Sodium Salt) | Phosphatidylserine | |
| DOPA-NA | 1,2-Dioleoyl-sn-glycero-3-phosphate (Sodium Salt) | Phosphatidic acid | |
| DOPC | 4235-95-4 | 1,2-Dioleoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
| DOPE | 4004-5-1- | 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine | Phosphatidylethanolamine |
| DOPG-NA | 62700-69-0 | 1,2-Dioleoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt) | Phosphatidylglycerol |
| DOPS-NA | 70614-14-1 | 1,2-Dioleoyl-sn-glycero-3-phosphoserine (Sodium Salt) | Phosphatidylserine |
| DPPA-NA | 71065-87-7 | 1,2-Dipalmitoyl-sn-glycero-3-phosphate (Sodium Salt) | Phosphatidic acid |
| DPPC | 63-89-8 | 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
| DPPE | 923-61-5 | 1,2-Dipalmitoyl-sn-glycero-3-phosphoethanolamine | Phosphatidylethanolamine |
| DPPG-NA | 67232-81-9 | 1,2-Dipalmitoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt) | Phosphatidylglycerol |
| DPPG-NH4 | 73548-70-6 | 1,2-Dipalmitoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Ammonium Salt) | Phosphatidylglycerol |
| DPPS-NA | 1,2-Dipalmitoyl-sn-glycero-3-phosphoserine (Sodium Salt) | Phosphatidylserine | |
| DSPA-NA | 108321-18-2 | 1,2-Distearoyl-sn-glycero-3-phosphate (Sodium Salt) | Phosphatidic acid |
| DSPC | 816-94-4 | 1,2-Distearoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
| DSPE | 1069-79-0 | 1,2-Distearoyl-sn-glycero-3-phosphoethanolamine | Phosphatidylethanolamine |
| DSPG-NA | 67232-82-0 | 1,2-Distearoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Sodium Salt) | Phosphatidylglycerol |
| DSPG-NH4 | 108347-80-4 | 1,2-Distearoyl-sn-glycero-3[Phospho-rac-(1-glycerol...) (Ammonium Salt) | Phosphatidylglycerol |
| DSPS-NA | 1,2-Distearoyl-sn-glycero-3-phosphoserine (Sodium Salt) | Phosphatidylserine | |
| Egg Sphingomyelin empty Liposome | |||
| EPC | Egg-PC | Phosphatidylcholine | |
| HEPC | Hydrogenated Egg PC | Phosphatidylcholine | |
| HSPC | High purity Hydrogenated Soy PC | Phosphatidylcholine | |
| HSPC | Hydrogenated Soy PC | Phosphatidylcholine | |
| LYSOPC MYRISTIC | 18194-24-6 | 1-Myristoyl-sn-glycero-3-phosphocholine | Lysophosphatidylcholine |
| LYSOPC PALMITIC | 17364-16-8 | 1-Palmitoyl-sn-glycero-3-phosphocholine | Lysophosphatidylcholine |
| LYSOPC STEARIC | 19420-57-6 | 1-Stearoyl-sn-glycero-3-phosphocholine | Lysophosphatidylcholine |
| Milk Sphingomyelin MPPC | 1-Myristoyl-2-palmitoyl-sn-glycero 3-phosphocholine | Phosphatidylcholine | |
| MSPC | 1-Myristoyl-2-stearoyl-sn-glycero-3–phosphocholine | Phosphatidylcholine | |
| PMPC | 1-Palmitoyl-2-myristoyl-sn-glycero-3–phosphocholine | Phosphatidylcholine | |
| POPC | 26853-31-6 | 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
| POPE | 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine | Phosphatidylethanolamine | |
| POPG-NA | 81490-05-3 | 1-Palmitoyl-2-oleoyl-sn-glycero-3[Phospho-rac-(1-glycerol)...] (Sodium Salt) | Phosphatidylglycerol |
| PSPC | 1-Palmitoyl-2-stearoyl-sn-glycero-3–phosphocholine | Phosphatidylcholine | |
| SMPC | 1-Stearoyl-2-myristoyl-sn-glycero-3–phosphocholine | Phosphatidylcholine | |
| SOPC | 1-Stearoyl-2-oleoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine | |
| SPPC | 1-Stearoyl-2-palmitoyl-sn-glycero-3-phosphocholine | Phosphatidylcholine |
See also
References
- ^ Campbell, Neil A. (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 0-13-250882-6.
{{cite book}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Lodish, Harvey (2008). Molecular Cell Biology. W.H. Freeman and Company. ISBN 0716776014.
{{cite book}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Se-Young Choi; et al. (2005). "Multiple Receptors Coupled to Phospholipase C Gate Long-Term Depression in Visual Cortex". The Journal of Neuroscience.
{{cite journal}}: Unknown parameter|author-separator=ignored (help) - ^ Darran G. Cronshaw; et al. (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.
{{cite journal}}: Unknown parameter|author-separator=ignored (help)