Job plot

A Job plot is used to determine the stoichiometry of a binding event. It is also known as the Method of Continuous Variation. In this method, the total molar concentration of the two binding partners (i.e. a protein and ligand) are held constant, but their mole fractions are varied. A measurable parameter that is proportional to complex formation (such as absorption signal or enzymatic activity) is plotted against the mole fractions of these two components. The maximum on the plot corresponds to the stoichiometry of the two species [Huang, C.Y. Determination of Binding Stoichiometry by the Continuous Variation Method: The Job Plot. "Methods in Enzymology" (1982) 87, 509-525.] . This method is named after P. Job, who first introduced this methodology in 1928 [Job, P. "Ann. Chim." (1928) 9, 113-203] .

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