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(organic chemistry)
A chemical process for introducing a methyl group (CH3‒) into an organic compound.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the replacement of a hydrogen, metal, or halogen atom by a methyl group,—CHs; it is effected by the action of various methylating agents—for example, methyl iodide, CH3I; dimethyl sulfate, (CH3O)2SO2; methylsulfuric acid, CH3OSO3H; methyl esters of organic sulfo acids; methanol, CHjOH; and dimethyl ether, (CH3)2O. Methylation is widely used in organic synthesis in industry. For example, methylation with dimethyl sulfate is used in the synthesis of pharmaceuticals (for example, metapyrin); amidopyrine is prepared by methylation with formaldehyde and a reducing agent, usually formic acid.

Aromatic hydrocarbons are readily methylated by the action of methyl chloride or dimethyl ether in the presence of AlCl3. Methylaniline and dimethylaniline are prepared industrially by methylation of aniline with methanol over A12O3 at high temperatures:

Methylation with diazomethane is widely used to produce methyl esters of carboxylic acids under laboratory conditions, according to the formula



The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Aberrant promoter methylation of the CD4 gene in peripheral blood cells of mastitic dairy cows.
MethPrimer: designing primers for methylation PCRs.
Methylation influences multiple mechanisms in the body by adding and subtracting methyl groups.
Because DNA methylation could be altered by genetic and environmental factors and can integrate the impact of both factors on a phenotype or disease (Schadt 2009), DNA methylation age may likewise reflect the environmentally induced effects on aging.
Also, we examined the LPL DNA methylation status relating these epigenetic factors to LPL gene and protein expression, as well as biochemical parameters associated with the etiology of MetS.
In the mammalian system, cytosine-5 methylation in tRNA has been shown to regulate [Mg.sup.2+] binding, anticodon stem-loop conformation, and secondary structure stabilization [21, 22].
Methylation is a chemical modification wherein a methyl group acts like light switches along the DNA molecule, turning some genetic activity on and some off.
Methylation profiles of CRC are widely studied to investigate and identify any molecular marker for early detection, any prognosis-related marker, and markers for diseases classification, therapeutic target, and also for risk assesment (23-26).
Multiple transcripts are encoded within the region 24,110,413-24,126,503 (GRch37-hp19 at: and expression is known to be altered by DNA methylation (Navarro et al., 2012).
ABCG2 expression has also been found to be regulated by histone acetylation and methylation. Demethylation of the promoter increased ABCG2 mRNA and protein expression in human multiple myeloma cells (Turner et al., 2006), and DNA methylation-dependent formation of a repressor complex in the CpG island contributes to inactivation of ABCG2(To et al., 2006).
Epigenetic modifications in the genome such as DNA methylation have been suggested to play a role in the processes involved in cardiovascular diseases.
In vertebrates, DNA methylation is a key epigenetic modification that plays an important role in a wide range of developmental and disease processes.[11] During embryogenesis, three active DNA methyltransferases, including DNMT-1, DNMT-3a, and DNMT-3b, primarily catalyze mammalian DNA methylation.