ABSTRACT
Minimal steric difference (MSD) usually helps for determining the fitting spatial characteristics of the binding site for a ligand molecule on its specific receptor. The physical-chemical and steric properties of the receptor but also of the molecule are very important for this mapping technique. It is the initial method of currently-used minimal topological difference method. The importance of the stereochemistry in the biological activity assessment of a molecule was recognized, and the interaction between the drug molecule and its macromolecular receptor is described as a “steric fit” guided by the “key-lock” principle. The MSD between a given molecule and its natural substrate is the non-overlapping volume of those lowest energy molecular conformations which permits a maximum overlap between the two molecules. MSD is very accurate for correlations implying amino acid replacements in biologically active oligopeptides. The hypermolecule spatially resembles to the cavity of the receptor where the ligands are binding.
