Acetyl group known as paracetamol), and acetylsalicylic acid (better known as aspirin). The introduction of an acetyl group into a molecule is called acetylation. In biological organisms, acetyl groups are commonly transferred from acetyl-CoA to other organic molecules. Acetyl-CoA is an intermediate both in the biological synthesis and in the breakdown of many organic molecules. Acetyl-CoA is also created during the second stage of cellular respiration, the Krebs Cycle, by the action of pyruvate dehydrogenase on pyruvic acid. Histones and other proteins are often modified by acetylation. For example, on the DNA level, histone acetylation by acetyltransferases (HATs) causes an expansion of
Phenylarsonic acid was first prepared by Michaelis and Loenser. X-ray crystallography indicates that the molecules are connected by hydrogen-bonds consistent with short distance of 2.5 Å separating the oxygen atoms. The arsenic center is tetrahedral. Several derivatives of phenylarsonic acid have been used as additives for animal feeds. These include 4-hydroxy-3-nitrobenzenearsonic acid (3-NHPAA, or Roxarsone), "p"-arsanilic acid ("p"-ASA), 4-nitrophenylarsonic acid (4-NPAA), and "p"-ureidophenylarsonic acid ("p"-UPAA). Phenylarsonic acid Phenylarsonic acid is the chemical compound with the formula CHAsO(OH), commonly abbreviated PhAsOH. This colourless solid is an organic derivative of arsenic acid, AsO(OH), where one OH group has been replaced by a phenyl group.