Quantitative Structure–Activity Relationships
Quantitative structure–activity relationships is the study of how the physicochemical properties of a series of compounds affect their biological activity. Quantitative values are measured or calculated for the physical features and these are related to biological activities using a mathematical equation. The overall hydrophobic character of a compound influences how efficiently it can cross cell membranes; the hydrophobic character and the size of individual substituents may influence how well the compound interacts and fits into its binding site, while the electronic character of substituents can influence the basicity of the compound, affecting both absorption and receptor binding. The electrostatic field can be calculated in a similar fashion. Since the probe atom is positively charged, favorable electrostatic interactions indicate regions of the molecule that are negative in character, while unfavorable electrostatic interactions will indicate regions of the molecule that are positive in character.