EPR-monitored binding experiments

The stoichiometric binding of compound A to compound B (which is identical to the binding of compound B to compound A) 

The Scatchard formalism can of course be applied to the binding of any small molecule to any biomacromolecule, such as the binding of a substrate or inhibitor to an enzyme, or the binding of a metal ion to an apoprotein. In receptor research, the determination of Kd typically requires labeling of the substrate by radioactivity or by fluorescence. However, we might just as well choose paramagnetism as the label, and this then makes the EPR spectrometer the detector for the determination of binding equilibria. The Scatchard plot in Equation 13.4 has two experimental observables [L] and [RL], and so we must find ways to determine these quantities from EPR spectra. 

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