Thermodynamic Parameters in Immunoassay
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Marc H. V. Van Regenmortel
Abstract
Although affinity and kinetic measurements on their own provide useful information regarding the suitability of antibodies for various immunoassays, a thermodynamic analysis provices additional information that throws light on the molecular forces at work in the antigen-antibody interaction. It may then be possible to adjust assay conditions in order to favour either the association or dissociation of antigen-antibody complexes. A tenfold increase in binding affinity (K) corresponds to a free energy change of only 1.4 kcal/mol (5.8 kJ/mol) at 25 °C. This means that K values of 105 M−1 and 1010 M−1 correspond to a free energy change (∆G) of 7.0 and 14.0 kcal/mol respectively. The entire range of affinity constants normally encountered in antigen-antibody interactions, therefore differs by no more than about 7 kcal/mol of free energy change, which is equivalent to only a few hydrogen bonds. In comparison, a single electrostatic interaction corresponds to about 4 kcal/mol of free energy change. A full description of the binding interaction requires an understanding of the change in hydration states of the reactants when the complex forms, and an assessment of the entropic andenthalpic effects of these changes. Contrary to earlier assumptions, it is now clear that antigen-antibody interactions are often accompanied by a large favourable enthalpy which more than compensates the unfavourable entropy.
Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- New Trends in Immunoassay Methodology
- Progress in Immunoassay Technology
- Standardization of Steroid Immunoassays – In Theory an Easy Task
- Thermodynamic Parameters in Immunoassay
- Engineering of an Anti-Steroid Antibody: Amino Acid Substitutions Change Antibody Fine Specificity from Cortisol Estradiol
- Antigenic Definition of Cardiac Troponin I
- Peptide Models of Immunological Recognition: Paratope Dissection by Multiple Peptide Synthesis
- Remodeling of Glycoprotein and Carbohydrate Antigens
- Strongly Enhanced Serum Levels of Vascular Endothelial Growth Factor (VEGF) after Poly-trauma and Burn
- Rapid Electrophoretic Separation of Pre-ß-Migrating High Density Lipoproteins Using Automated PhastSystem(tm): Application to Analysis of Lecitihin: Cholesterol Acyltransferase-Deficient Plasma
- Decrease in High Density Lipoprotein Cholesterol (HDL-C) Levels Following Gemfibrozil Therapy
- Reference Intervals for Serum Cystatin C and Serum Creatinine in Adults
- Concepts for a Model of Good Medical Laboratory Services
- Diagnostic Kits Derived from Standard Method "DGKC 94" as a Potential Tool for Improvement of Analytical Standardization and Clinical Utility of Alkaline Phosphatase
- Antioxidant Interferences in Superoxide Dismutase Activity Methods Using Superoxide Radical as Substrate
- Cytokines and Soluble Adhesion Molecules in Laboratory Diagnostics. Report from a Meeting Held at the German Cancer Research Center in Heidelberg on 25 November 1997
- IFCC-WorldLabNews
