IC50

Definition

IC50 (half maximal inhibitory concentration) is the molar concentration of a compound required to inhibit a defined biological process or receptor-mediated response by 50% in a specific assay system. It is a widely used parameter for characterizing the potency of inhibitory compounds at enzymes, receptors, ion channels, or cellular processes. IC50 values are determined from full inhibition curves by fitting sigmoidal dose-response models to the experimental data. Lower IC50 values indicate greater potency. IC50 values are assay-specific and cannot be directly compared between different experimental systems without careful standardization.

Research Context

IC50 measurement is a standard analytical tool in peptide research for characterizing the inhibitory potency of compounds at their molecular targets. For receptor antagonists, IC50 values from competition binding assays are used to calculate the inhibition constant Ki, which is an intrinsic affinity measure independent of assay conditions. For enzyme inhibitors, IC50 values characterize the effectiveness of a compound at blocking catalytic activity. IC50 data is commonly reported alongside selectivity profiles across multiple targets to characterize the specificity of a research compound.