unformylated

Unformylated describes a molecule that lacks a formyl group, a formyl substituent consisting of a single carbonyl group linked to a hydrogen (-CHO) that can be attached to another atom. The term is used across chemistry and biochemistry to contrast a molecule with a formyl modification with its unmodified state.

In biology, unformylated is often used in the context of proteins and amino acids. In bacteria, translation begins with N-formylmethionine, so nascent polypeptides initially carry a formyl group at the N-terminus. Through action of peptide deformylase and, in some cases, methionine aminopeptidase, the formyl group and sometimes the methionine are removed, producing an unformylated N-terminus in mature proteins. Eukaryotes and many archaea typically synthesize and maintain unformylated methionine residues at the start of proteins, reflecting different initiation mechanisms.

Formylated peptides are well known as signals for formyl peptide receptors in animals; unformylated variants generally do not act as ligands for these receptors, though they can serve other biological roles or be used as controls in experiments.

In analytical contexts, unformylated compounds lack a formyl substituent either by design or by subsequent chemical/enzymatic removal, which can affect reactivity, detection, and biological activity.

See also: Formyl group; Formylation; N-formylmethionine; Peptide deformylase; Formyl peptide receptor.