pentamer

A pentamer is a molecule or molecular assembly composed of five subunits or monomer units. The five components may be identical (a homopentamer) or of different types (a heteropentamer), and the subunits may be covalently linked or held together by noncovalent interactions. Pentamers can be linear assemblies or cyclic structures in which the five subunits form a closed ring.

In biology and biochemistry, pentameric organization is common among proteins and receptors. Pentameric ligand-gated ion channels, including nicotinic acetylcholine receptors and GABAA receptors, are composed of five subunits arranged around a central pore that conducts ions. Immunoglobulin M (IgM) antibodies commonly exist as a pentamer in circulation, often with a joining chain that links the five monomer units.

In polymer chemistry, a pentamer refers to a oligomer with a degree of polymerization of five, i.e., five repeating units. Pentamers can be linear or cyclic and may serve as model compounds for studying the properties of short oligomers or as building blocks for larger materials.

The assembly into pentamers affects stability, binding properties, and function. Pentameric structures are studied by techniques such as X-ray crystallography, cryo-electron microscopy, and mass spectrometry to understand subunit interfaces and cooperative effects.