Misuse of nonlinear Scatchard plots.

Scatchard plots--plots of bound/free ligand vs bound ligand--are a common graphical presentation of binding data. They are often nonlinear. Despite examples of correct usage and several articles calling attention to incorrect treatment of Scatchard plots, erroneous interpretations of nonlinear Scatchard plots remain frequent; plots are resolved incorrectly into two or more linear components which have no relation to an acceptable binding model. Correct analysis requires determination, usually by computer, of numerical values of the binding parameters that give the best nonlinear fit to an appropriate model, examples of which are specified.