{"term":{"id":"14112","title":"binding isotherm","longtitle":"IUPAC Gold Book - binding isotherm","doi":"10.1351\/goldbook.14112","code":"14112","status":"current","definitions":[{"id":1,"text":"Graphical representation of the relationship between the amount of ligand that is specifically bound to a receptor per mass of binding material and the amount of free ligand.","notes":{"1":"For a system containing a single binding site and lacking cooperative interactions, the binding isotherm is described by \\[B = B_{\\max}[\\ce{L}]\/(K_{\\rm{d}} + [\\ce{L}])\\] where \\(\\ce{B}\\) is the amount of ligand specifically bound, \\([\\ce{L}]\\) is the amount concentration of free ligand, \\(K_{\\rm{d}}\\) is the equilibrium dissociation constant of the ligand, and \\(B_{\\rm{max}}\\) is the maximal specific binding of a ligand. The equation describes a hyperbola with \\(B_{\\rm{max}}\\) as the asymptote. \\(B_{\\rm{max}}\\) is defined quantitatively as the amount of ligand bound per mass of binding material, with units, e.g., \\(\\pu{pmol mg-1}\\).","2":"A Scatchard plot was formerly used to determine \\(B_{\\rm{max}}\\) and \\(K_{\\rm{d}}\\). It is now more common to determine these parameters by nonlinear least-squares fitting to the binding equation given above.","3":"The total number of receptors or binding sites in the system is proportional to \\(B_{\\rm{max}}\\)."},"sources":["PAC, 2011, 83, 1129. 'Glossary of terms used in biomolecular screening (IUPAC Recommendations 2011)' on page 1133 (https:\/\/doi.org\/10.1351\/PAC-REC-09-05-03)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/14112\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/14112\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/14112\/plain"},"citation":"Citation: 'binding isotherm' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.14112","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-05-10T03:22:46+00:00"}}