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Measuring antibody affinity and performing immunoassay at the single molecule level
Sergey Y Tetin1, Kerry M Swift, Edmund D Matayoshi
1Drug Monitoring, Abbott Diagnostics Division, Abbott Park, IL 60064-6016, USA. sergey.tetin@abbott.com
Analytical Biochemistry
|July 26, 2002
Summary
Fluorescence correlation spectroscopy (FCS) accurately measures antibody-hapten binding constants. This technique can also quantify analytes like vancomycin in biological samples using an immunoassay format.
Area of Science:
- Biophysical Chemistry
- Analytical Chemistry
- Immunochemistry
Background:
- Fluorescence correlation spectroscopy (FCS) is a powerful technique for observing single fluorescent molecules in solution.
- Understanding molecular interactions, such as hapten-antibody binding, is crucial in various biological and diagnostic applications.
- Existing methods for determining binding constants and analyte concentrations can be time-consuming or require large sample volumes.
Purpose of the Study:
- To demonstrate the utility of FCS for determining equilibrium binding constants of hapten-antibody interactions.
- To validate FCS as a method for quantitative analysis in an immunoassay format.
- To assess the potential of FCS for measuring analyte concentrations in biological samples.
Main Methods:
- Utilized FCS to analyze the translational diffusion of fluorescently labeled haptens (digoxigenin and vancomycin) in the presence of antibodies.
- Determined fractional amounts of free and bound hapten by analyzing FCS data.
- Compared FCS-derived equilibrium dissociation constants with those obtained from fluorescence polarization measurements.
- Developed a calibration curve using FCS data for vancomycin concentration determination in an immunoassay.
Main Results:
- FCS analysis yielded equilibrium dissociation constants for anti-digoxin antibodies and fluorescein-labeled digoxigenin that were identical to those obtained by fluorescence polarization.
- Demonstrated the ability of FCS to monitor competitive displacement of a tracer from an antibody by an unlabeled analyte.
- Successfully generated a calibration curve for vancomycin concentration using FCS, showing its applicability in biological samples.
Conclusions:
- FCS is a reliable method for determining equilibrium binding constants of antibody-hapten systems.
- FCS can be effectively employed in an immunoassay format for quantitative analyte detection.
- The FCS approach offers a sensitive and accurate method for measuring concentrations of analytes like vancomycin in complex biological matrices.