Polar surface area

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

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PSA is a commonly used medicinal chemistry metric for the optimisation of cell permeability. Molecules with a polar surface area of greater than 140 angstroms squared are usually believed to be poor at permeating cell membranes. For molecules to penetrate the blood-brain barrier, PSA should be less than 60 angstroms squared.

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)