Acetylation is a chemical process where an acetyl group (−COCH₃) is added to a molecule, often modifying its properties and functions. This reaction commonly occurs in organic chemistry and biochemistry, affecting various compounds, including proteins and drugs. Acetylation can influence the activity, stability, and interactions of these molecules. In biological systems, acetylation plays a crucial role in regulating gene expression and protein function. For example, the acetylation of histones, which are proteins that package DNA, can alter how tightly DNA is wound, impacting gene expression. This modification is essential for processes like cell differentiation and metabolism.