Polar surface area (in red) of Paracetamol

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

PSA is a commonly used medicinal chemistry metric for the optimisation of cell permeability. Molecules with a polar surface area of greater than 1.4 square nanometres are usually believed to be poor at permeating cell membranes. For molecules to penetrate the blood-brain barrier (and thus acting on receptors in the central nervous system), PSA should be less than 0.6 square nanometres.

[edit] See also

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

[edit] 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

[edit] External links

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

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