Picomolar

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Unit system
Unit of
Symbol	pM
Named after

Picomolar (pM) is a unit of molar concentration that is equal to 10^-12 moles per liter (mol/L). It is commonly used in the field of biochemistry and molecular biology to describe the concentration of very low-abundance molecules, such as hormones, enzymes, or nucleic acids in a solution.

Definition

The picomolar concentration is defined as one trillionth (10^-12) of a mole per liter. This unit is part of the International System of Units (SI) and is used to express concentrations that are much lower than those typically encountered in chemical reactions.

Applications

In the field of biochemistry, picomolar concentrations are often used to measure the binding affinity of ligands to receptors, the activity of enzymes, or the concentration of biomarkers in biological samples. For example, the dissociation constant (K_d) of a ligand-receptor interaction might be in the picomolar range, indicating a very high affinity between the ligand and the receptor.

In molecular biology, picomolar concentrations are relevant when dealing with DNA or RNA samples, especially in techniques such as quantitative PCR (qPCR) or next-generation sequencing (NGS), where precise quantification of nucleic acids is crucial.

Measurement

Measuring picomolar concentrations requires sensitive analytical techniques. Common methods include:

• Mass spectrometry
• Fluorescence spectroscopy
• Surface plasmon resonance (SPR)
• Isothermal titration calorimetry (ITC)

These techniques can detect and quantify molecules at very low concentrations, making them suitable for applications in pharmacology, diagnostics, and biotechnology.

Conversion

To convert picomolar concentrations to other units of concentration, the following conversions can be used:

• 1 pM = 10^-12 M (molar)
• 1 pM = 10^-9 mM (millimolar)
• 1 pM = 10^-6 µM (micromolar)

Also see

• Molar concentration
• Nanomolar
• Micromolar
• Binding affinity
• Ligand (biochemistry)