Polar surface area

Polar surface area (in red) of paracetamol

The polar surface area (PSA) of a molecule is defined as the surface sum over all polar atoms, primarily oxygen and nitrogen, also including their attached hydrogens.

PSA is a commonly used medicinal chemistry metric for the optimisation of a drug's ability to permeate cells. Molecules with a polar surface area of greater than 140 angstroms squared tend to be poor at permeating cell membranes. For molecules to penetrate the blood-brain barrier (and thus act on receptors in the central nervous system), a PSA less than 60 angstroms squared is usually needed.

See also

• Lipinski's Rule of Five
• Biopharmaceutics Classification System
• Implicit solvation
• Cheminformatics
  • Chemistry Development Kit
  • JOELib

References

• Ertl, P., Rohde, B., Selzer, P. Fast calculation of molecular polar surface area as a sum of fragment based contributions and its application to the prediction of drug transport properties. J. Med. Chem. 2000, 43, 3714–3717. (doi:10.1021/jm000942e)
• Ertl, P. Polar Surface Area, in Molecular Drug Properties, R. Mannhold (ed), Wiley-VCH, pp. 111–126, 2007

External links

• Interactive Polar Surface Area calculator
• Free, Programmable TPSA Calculator