120nM

120nM refers to a concentration of a substance in a solution. The unit nM stands for nanomolar, which is a unit of molar concentration. One molar (M) is equal to one mole of a substance per liter of solution. Therefore, one nanomolar (nM) is equal to one billionth of a mole per liter, or 1 x 10^-9 moles per liter. So, a concentration of 120nM means that there are 120 billionths of a mole of the substance dissolved in every liter of the solution. This is a very dilute concentration, often encountered in fields like molecular biology, biochemistry, and pharmacology, where very small quantities of molecules are relevant. For example, many enzymes have optimal activity at nanomolar concentrations of their substrates or inhibitors, and drug concentrations in biological fluids are frequently measured in these units. Understanding nanomolar concentrations is crucial for interpreting experimental results and designing biological assays.