Methylation

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methylation

[‚meth·ə′lā·shən]
(organic chemistry)
A chemical process for introducing a methyl group (CH3‒) into an organic compound.

Methylation

 

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

R—COOH + CH2N2→RCOOCH3 + N2

B. L. DIATKIN

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The investigators found a higher percentage of DMA in the participants' urine, reflecting the association between higher methylation capacity and increased risk of diabetes.
Arsenic and Diabetes: Assessing Risk at Low-to-Moderate Exposures
Familial aggregation and heritability analyses of arsenic metabolic profiles suggest that genetic factors influence interi ndividual variation in arsenic methylation capacity (Chung et al.
The genetic architecture of arsenic metabolism efficiency: a SNP-based heritability study of Bangladeshi adults
The intracellular AdoMet/AdoHcy ratio has been used as a predictor of cellular methylation capacity. A significant correlation between plasma and lymphocyte AdoMet/AdoHcy ratios has been reported (12).
Increased homocysteine and S-adenosylhomocysteine concentrations and DNA hypomethylation in vascular disease
We conducted a prospective case--cohort study nested in a large prospective cohort to assess associations of arsenic exposure from drinking water and arsenic methylation capacity, indicated using relative distribution of urinary arsenic metabolites, with CVD risk.
A prospective study of arsenic exposure, arsenic methylation capacity, and risk of cardiovascular disease in Bangladesh
(2011) also reported associations between dietary intake of several nutrients (assessed using a modified 24-hr recall) and As methylation capacity. One of the most critical and widely discussed issues in nutritional epidemiology is the method used to adjust for total energy intake (TEI) (Willett et al.
Relationship of creatinine and nutrition with Arsenic metabolism
Indeed, BD exposure induced profound DNA damage, especially the formation of N-7 guanine adducts, whose presence may profoundly compromise the methylation capacity of Dnmtl, as has been observed with other guanine adducts (Valinluck and Sowers 2007).
Epigenetic alterations in liver of C57BL/6J mice after short-term inhalational exposure to 1,3-butadiene
The influence of the M287T (T[right arrow]C) polymorphism in the AS3MT gene on the methylation capacity was much more pronounced in men than in women.
Metabolism of low-dose inorganic arsenic in a central european population: influence of sex and genetic polymorphisms
The relationship between methylation capacity and skin lesions needs further investigation.
Arsenic methylation, GSTT1, GSTM1, GSTP1 polymorphisms, and skin lesions
Urinary As metabolites measured in a subset of 300 study participants showed a wide interindividual variability in arsenic methylation capacity. For example, the percentage of total urinary As present as DMA (%DMA) ranged from 20 to 90%, with the majority falling between 50 and 80% (Figure 3).
Folate, homocysteine, and arsenic metabolism in arsenic-exposed individuals in Bangladesh
Determinants of inorganic arsenic methylation capacity among residents of the Lanyang Basin, Taiwan: arsenic and selenium exposure and alcohol consumption.
Dietary intake and arsenic methylation in a U.S. population
The relative distribution of urinary In-As, MMA, and DMA is still considered an adequate indicator of methylation capacity after exposure to In-As, although the interpretation of the findings in terms of detoxification versus toxification is currently an area of active investigation (Styblo 2002; Vahter and Concha 2001).
Profile of urinary arsenic metabolites during pregnancy
[As.sub.inorg]/[As.sub.methyl] and MMA/DMA were calculated as metabolic indices to measure the stepwise methylation capacity. Detailed information on the urine sampling, storage, and As speciation has been previously reported (Nieuwenhuijsen et al.
Association between arsenic exposure from a coal-burning power plant and urinary arsenic concentrations in Prievidza District, Slovakia. (Research)

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