Binding Affinity vs \u0394G vs Ki vs IC50: Untangling the Units

By BioDockify Computational Research Team · September 26, 2026 · Reference

Binding affinity vs ΔG vs Ki vs Kd vs IC50 — definitions, the ΔG = RT ln K relationship, Cheng-Prusoff conversions, assay dependence, and reporting correctly in papers.

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Key References

• Cheng, Y. & Prusoff, W.H. Relationship between inhibition constant (K1) and concentration of inhibitor which causes 50 per cent inhibition (I50) of an enzymatic reaction. Biochem. Pharmacol. 22, 3099-3108 (1973).
• Ferreira, L.G. et al. Molecular docking and structure-based drug design strategies. Molecules 20, 13384-13421 (2015).

Scope & Limitations

Conversions assume standard conditions and competitive mechanisms IC50 comparisons require matched assays