Acetylation describes a reaction, usually with acetic acid, that introduces an acetyl functional group into an organic compound. The chemical compound acetic acid (from the Latin word acetum, meaning vinegar), systematically called ethanoic acid, is the acid that gives vinegar its sour taste and very pungent smell when at high concentrations. ... Acetyl is the radical of acetic acid. ... In ecology functional groups are collections of organisms based on morphological, physiological, behavioral, biochemical, or environmental responses or on trophic criteria. ... An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with exception of carbides, carbonates and carbon oxides. ...

Moreover, it is that process of introducing an acetyl group into a compound, specifically, the substitution of an acetyl group for an active hydrogen atom. A reaction involving the replacement of the hydrogen atom of an hydroxyl group with an acetyl group (CH₃ CO) to yield a specific ester, the acetate. Acetic anhydride is commonly used as an acetylating agent reacting with free hydroxyl groups. Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: −O−H It has a charge of −1. ... In organic chemistry and biochemistry, esters are organic compounds where an organic group (symbolyzed by R in this article) replaces a hydrogen atom (or more than one) in an oxygen acid. ... Acetate, or ethanoate, is the anion of a salt or ester of acetic acid. ...

In biology, i.e. in living cells, acetylation is used as a post-translational modification of proteins. For example, histones are acetylated and deacetylated on lysine residues in the N-terminal tail as part of gene regulation. Typically, these reactions are catalyzed by enzymes with "histone acetyltransferase" (HAt) or "histone deacetylase" (HDAc) activity. The source (target) of the acetyl group in histone (de)acetylation is Acetyl Coenzyme A (AcCoA). Posttranslational modification means the chemical modification of a protein after its translation. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... In biology, histones are the chief proteins of chromatin. ... Gene regulation is the general term for cellular control of protein synthesis at the DNA-RNA transcription step. ... Ribbon diagram of the catalytically perfect enzyme TIM. Factor D enzyme crystal prevents the immune system from inappropriately running out of control. ...

Acetylated histones and nucleosomes represent a type of epigenetic tag within chromatin. Acetylation brings in a negative charge and neutralizes the interaction of the N termini of histones with the phosphate groups of DNA. As a consequence, the condensed chromatin is transformed into a transiently relaxed structure which allows genes to be transcribed. Acetylated chromatin is thought to be more "relaxed" and is called euchromatin. Methylated chromatin is more condensed (tightly packed), and referred to as heterochromatin. A nucleosome is a unit made of DNA and histones. ...