|
|Section2= |Section6= |Section7= }} Polyethylene glycol (PEG) is a polyether compound with many applications from industrial manufacturing to medicine. The structure of PEG is (note the repeated element in parentheses): : H-(O-CH2-CH2)n-OHPEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular weight. ==Available forms and nomenclature== PEG, PEO, or POE refers to an oligomer or polymer of ethylene oxide. The three names are chemically synonymous, but historically PEG is preferred in the biomedical field, whereas PEO is more prevalent in the field of polymer chemistry. Because different applications require different polymer chain lengths, PEG has tended to refer to oligomers and polymers with a molecular mass below 20,000 g/mol, PEO to polymers with a molecular mass above 20,000 g/mol, and POE to a polymer of any molecular mass.〔For example, in the (online catalog ) of Scientific Polymer Products, Inc., poly(ethylene glycol) molecular weights run up to about 20,000, while those of poly(ethylene oxide) have six or seven digits.〕 PEG and PEO are liquids or low-melting solids, depending on their molecular weights. PEGs are prepared by polymerization of ethylene oxide and are commercially available over a wide range of molecular weights from 300 g/mol to 10,000,000 g/mol. While PEG and PEO with different molecular weights find use in different applications, and have different physical properties (e.g. viscosity) due to chain length effects, their chemical properties are nearly identical. Different forms of PEG are also available, depending on the initiator used for the polymerization process – the most common initiator is a monofunctional methyl ether PEG, or methoxypoly(ethylene glycol), abbreviated mPEG. Lower-molecular-weight PEGs are also available as purer oligomers, referred to as monodisperse, uniform, or discrete. Very high purity PEG has recently been shown to be crystalline, allowing determination of a crystal structure by x-ray diffraction. Since purification and separation of pure oligomers is difficult, the price for this type of quality is often 10-1000 fold that of polydisperse PEG. PEGs are also available with different geometries. * ''Branched'' PEGs have three to ten PEG chains emanating from a central core group. * ''Star'' PEGs have 10 to 100 PEG chains emanating from a central core group. * ''Comb'' PEGs have multiple PEG chains normally grafted onto a polymer backbone. The numbers that are often included in the names of PEGs indicate their average molecular weights (e.g. a PEG with n = 9 would have an average molecular weight of approximately 400 daltons, and would be labeled PEG 400. Most PEGs include molecules with a distribution of molecular weights (i.e. they are polydisperse). The size distribution can be characterized statistically by its weight average molecular weight (Mw) and its number average molecular weight (Mn), the ratio of which is called the polydispersity index (Mw/Mn). MW and Mn can be measured by mass spectrometry. PEGylation is the act of covalently coupling a PEG structure to another larger molecule, for example, a therapeutic protein, which is then referred to as a PEGylated protein. PEGylated interferon alfa-2a or −2b are commonly used injectable treatments for Hepatitis C infection. PEG is soluble in water, methanol, ethanol, acetonitrile, benzene, and dichloromethane, and is insoluble in diethyl ether and hexane. It is coupled to hydrophobic molecules to produce non-ionic surfactants.〔Moritz Winger, Alex H. de Vries & Wilfred F. van Gunsteren. Force-field dependence of the conformational properties of α,ω-dimethoxypolyethylene glycol. Molecular Physics, 107 (13) pp 1313-1321. 10 July 2009.〕 PEGs contain potential toxic impurities, such as ethylene oxide and 1,4-dioxane. Ethylene Glycol and its ethers are nephrotoxic if applied to damaged skin. Polyethylene glycol (PEG) and related polymers (PEG phospholipid constructs) are often sonicated when used in biomedical applications. However, as reported by Murali et al., PEG is very sensitive to sonolytic degradation and PEG degradation products can be toxic to mammalian cells. It is, thus, imperative to assess potential PEG degradation to ensure that the final material does not contain undocumented contaminants that can introduce artifacts into experimental results. Murali et al., Exp Biol Med (Maywood), September 2015, volume 240, pages 1147-1151, doi: 10.1177/1535370214567615 PEGs and methoxypolyethylene glycols are manufactured by Dow Chemical under the tradename ''Carbowax'' for industrial use, and ''Carbowax Sentry'' for food and pharmaceutical use. They vary in consistency from liquid to solid, depending on the molecular weight, as indicated by a number following the name. They are used commercially in numerous applications, including as surfactants, in foods, in cosmetics, in pharmaceutics, in biomedicine, as dispersing agents, as solvents, in ointments, in suppository bases, as tablet excipients, and as laxatives. Some specific groups are lauromacrogols, nonoxynols, octoxynols, and poloxamers. Macrogol, used as a laxative, is a form of polyethylene glycol. The name may be followed by a number which represents the average molecular weight (e.g. macrogol 4000, macrogol 3350 or macrogol 6000). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Polyethylene glycol」の詳細全文を読む スポンサード リンク
|