Many molecules undergo spontaneous ionization in aqueous (or more generally, protic) media, which is quantified by the reaction equilibrium constant of proton dissociation or uptake, following the Bro̷nsted-Lowry acid-base theory. By convention, pKa, the negative logarithm of proton dissociation is used most widely for downstream applications, particularly in the fields of medicinal chemistry and drug discovery. Ionization states can have a drastic effect on physicochemical properties such as solvation, lipophilicity, membrane permeability and supramolecular interactions, all of them being crucially important aspects of drug affinity and safety. Enumerating ionized states for small molecules is especially important for structure-based molecular modelling and virtual screening workflows, as the protonation state of the ligand greatly affects the type and strength of secondary interaction with protein binding sites.

pKahub is a convenient starting point for viewing and downloading charge state-annotated pKa data, providing access to the largest collection of public pKa datasets, to date. You can browse individual molecules or datasets and download the relevant data in several formats.

Read more about pKa and charge state transitions in general, as well as about our methodology for assigning and annotating pKa values to charge state transitions in the About page.

If you use pKahub in your work, please cite our primary paper: To be published