Methylation

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

methylation

[meth″ĭ-la´shun] the addition of methyl groups.

meth·yl·a·tion

(meth-i-lā'shŭn), Addition of methyl groups; in histochemistry, used to esterify carboxyl groups and remove sulfate groups by treating tissue sections with hot methanol in the presence of hydrochloric acid, the net effect being to reduce tissue basophilia and abolish metachromasia.

methylation

Chemistry
The addition of a methyl group to a molecule.

Molecular biology
The addition of a methyl group to a cytosine residue on double-stranded DNA, a process which plays a major role in regulating gene expression and preventing restriction endonucleases from cutting DNA at their recognition sites.

Methylated genes are inactive; the pattern of methylation or imprinting is critical in gene expression, and may be passed from one generation to the next. Genes may be demethylated or methylated de novo according to the cell’s function, or during normal development. Phosphorylation is another form of semi-permanent gene control.

meth·yl·a·tion

(meth'i-lā'shŭn) Addition of methyl groups; in histochemistry, used to esterify carboxyl groups and remove sulfate groups by treating tissue sections with hot methanol in the presence of hydrochloric acid; the net effect being to reduce tissue basophilia and abolish metachromasia.

methylation

the addition of a methyl group (-CH₃) to an AMINO ACID in a PROTEIN, as in, for example, POST-TRANSLATIONAL MODIFICATION, or to a NUCLEOTIDE in a NUCLEIC ACID; see MODIFICATION AND RESTRICTION SYSTEM. See also METHYL TRANSFERASE.

单词	methylation
释义	methylation meth·yl·a·tion M5273350 (mĕth′ə-lā′shən)n.1. An alkylation process involving addition of, or substitution by, a methyl group.2. The process of treating something with methyl alcohol. Translations метилирование Methylation 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 methylation methylation [meth″ĭ-la´shun] the addition of methyl groups. meth·yl·a·tion (meth-i-lā'shŭn), Addition of methyl groups; in histochemistry, used to esterify carboxyl groups and remove sulfate groups by treating tissue sections with hot methanol in the presence of hydrochloric acid, the net effect being to reduce tissue basophilia and abolish metachromasia. methylation Chemistry The addition of a methyl group to a molecule. Molecular biology The addition of a methyl group to a cytosine residue on double-stranded DNA, a process which plays a major role in regulating gene expression and preventing restriction endonucleases from cutting DNA at their recognition sites. Methylated genes are inactive; the pattern of methylation or imprinting is critical in gene expression, and may be passed from one generation to the next. Genes may be demethylated or methylated de novo according to the cell’s function, or during normal development. Phosphorylation is another form of semi-permanent gene control. meth·yl·a·tion (meth'i-lā'shŭn) Addition of methyl groups; in histochemistry, used to esterify carboxyl groups and remove sulfate groups by treating tissue sections with hot methanol in the presence of hydrochloric acid; the net effect being to reduce tissue basophilia and abolish metachromasia. methylation the addition of a methyl group (-CH₃) to an AMINO ACID in a PROTEIN, as in, for example, POST-TRANSLATIONAL MODIFICATION, or to a NUCLEOTIDE in a NUCLEIC ACID; see MODIFICATION AND RESTRICTION SYSTEM. See also METHYL TRANSFERASE. meth·yl·a·tion (meth'i-lā'shŭn) Addition of methyl groups; in histochemistry, used to esterify carboxyl groups and remove sulfate groups by treating tissue sections with hot methanol in the presence of hydrochloric acid.
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