{"data":{"id":87,"name":" Intrinsic (Molecular) Permeability Measured by PAMPA","abbreviation":"Mol_PAMPA","description":"

The Parallel Artificial Membrane Permeability Assay (PAMPA) is a method for evaluating passive membrane permeability across an artificial lipid membrane. Besides the commonly reported apparent permeability, PAMPA can also determine intrinsic permeability<\/strong>, which reflects the permeability of the uncharged form of a compound through the membrane itself. Unlike apparent permeability, intrinsic permeability is corrected for the effects of the unstirred water layer (UWL) and the ionization state of the compound, providing a physicochemical property that is independent of experimental conditions such as pH and aqueous diffusion limitations. Intrinsic permeability is obtained by measuring effective permeability over a range of donor pH values and fitting the data to a pH\u2013permeability model that separates membrane permeability from aqueous boundary layer resistance. Because it removes external diffusion limitations, intrinsic permeability enables more direct comparisons between compounds and better reflects passive diffusion through lipid membranes. In contrast, apparent permeability includes the influence of UWL resistance and therefore represents the experimentally observed transport rate rather than the intrinsic membrane-crossing ability of the molecule.<\/p>

Table: Key differences between apparent permeability and intrinsic permeability measured by PAMPA.<\/p>

Feature<\/p><\/th>

Apparent permeability<\/p><\/th>

Intrinsic permeability<\/strong><\/p><\/td><\/tr>

Represents<\/strong><\/p><\/td>

Overall experimentally observed transport<\/p><\/td>

Passive diffusion through the membrane itself<\/p><\/td><\/tr>

Includes UWL effects<\/strong><\/p><\/td>

Yes<\/p><\/td>

No<\/p><\/td><\/tr>

Affected by ionization (pH)<\/strong><\/p><\/td>

Yes<\/p><\/td>

Corrected for ionization<\/p><\/td><\/tr>

Determination<\/strong><\/p><\/td>

Directly measured<\/p><\/td>

Calculated from pH-dependent permeability data using a permeability model<\/p><\/td><\/tr><\/tbody><\/table>","categories":[{"id":168,"title":"Permeability","breadcrumb":[{"id":4,"title":"Experimental"},{"id":168,"title":"Permeability"}]}],"url":"https:\/\/molmedb.upol.cz\/api\/v1\/methods\/87","landing_page":"https:\/\/molmedb.upol.cz\/method\/87","created_at":"2022-03-19T15:42:00.000000Z","updated_at":"2026-07-08T10:32:35.000000Z"}}