nanomolar

Nanomolar is a unit of concentration derived from the metric prefixes for molarity. It denotes one nanomole per liter, equal to 1×10^-9 moles per liter (M). In practical terms, 1 nM corresponds to about 6.022×10^14 molecules per liter in an ideal solution, using Avogadro’s number.

Used widely in chemistry, biology, and pharmacology, nanomolar describes the amount of a substance in a given volume. It is common to report substrate concentrations, enzyme inhibitors, and binding affinities in nanomolar. For example, a dissociation constant (Kd) in the nanomolar range indicates strong binding between a ligand and its target; picomolar (pM) range indicates even tighter binding. In biological contexts, many signaling molecules and drugs exert effects at nanomolar concentrations.

Relation to other concentration units: 1 µM equals 1×10^-6 M, which is 1000 nM. Therefore, nanomolar is 0.001 µM. When expressing concentrations in assays or cell culture media, it is important to specify the unit and conditions, because activity depends on temperature, pH, and ionic strength.

Measurement and reporting: Nanomolar concentrations are determined by analytical techniques such as fluorescence-based assays, spectroscopy, high-performance liquid chromatography, or mass spectrometry, depending on the substance. The term itself is a conventional concentration unit rather than a physical constant, and it is context-dependent.