The Scatchard Equation for a Multivalent Ligand: A Much Needed but Neglected Expression Required for Valid Interpretation of Biphasic Bioassays

Attention is drawn to the availability of a version of the Scatchard expression that accommodates multivalence of the ligand. Its lack of application over the past four decades by biological researchers is surprising in view of the popularity of its univalent counterpart. This summary of its derivation and limited application presents published examples of situations where the curvilinearity of conventional Scatchard plots has been misinterpreted as signifying heterogeneity or negative cooperativity of binding sites on erythrocyte ghosts instead of tetravalence of glycolytic enzymes in their interaction with band 3 protein. Also presented is the rectangular hyperbolic relationship of which the generalized Scatchard expression is the linear transform.