IC50-to-Ki

IC50-to-Ki converts experimentally determined IC_50 values into inhibition constant (K_i) estimates for enzyme and macromolecule–ligand inhibition studies involving proteins and polynucleic acids.

Key Features:

• Mechanism-Specific Calculations: Accommodates various inhibitor mechanisms, distinguishing classical and nonclassical inhibitors and accounting for tightly bound interactions that require consideration of free concentrations of reacting species.
• User-Defined Inputs: Requires total enzyme or target molecule concentration, substrate or ligand concentration, Michaelis constant (K_m) or dissociation constant (K_d), and IC_50 for conversion to K_i.
• Assumptions and Caveats: Includes explicit statements of assumptions and limitations that affect the accuracy of estimated K_i values.
• Literature-Based Examples: Provides examples from the scientific literature illustrating application of the IC_50-to-K_i conversion in real-world cases.
• Host Database Integration: Integrates with a host database containing kinetic constants and related data for inhibitors of proteolytic clostridial neurotoxins.

Scientific Applications:

• Drug Candidate Evaluation: Enables derivation of K_i from IC_50 measurements to compare inhibitor potency in pharmacological research.
• Enzymology and Binding Studies: Supports enzymology and molecular biology investigations of protein–ligand and polynucleic acid–ligand interactions by providing assumption-aware K_i estimates.

Methodology:

Computational conversion formulas account for mechanism-specific factors using inputs of total enzyme or target concentration, substrate or ligand concentration, K_m or K_d, and IC_50, with explicit guidance on underlying assumptions.