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.

Additional recommended knowledge

Daily Sensitivity Test

Essential Laboratory Skills Guide

Daily Visual Balance Check

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)