Binding Affinity Measurement
Binding Affinity Measurement - Related Videos
10:22
Protein Purification-free Method of Binding Affinity Determination by Microscale Thermophoresis
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Cited by 54 •
2013
Microscale thermophoresis (MST) can be widely used for determination of binding affinity without purification of the target protein from cell lysates. The protocol involves overexpression of the GFP-fused protein, cell lysis in non-denaturing conditions, and detection of MST signal in the presence of varying concentrations of the ligand.
06:17
Measuring Protein Binding to F-actin by Co-sedimentation
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Cited by 18 •
2017
This protocol describes a method to test the ability of a protein to co-sediment with filamentous actin (F-actin) and, if binding is observed, to measure the affinity of the interaction.
10:37
Comparing the Affinity of GTPase-binding Proteins using Competition Assays
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Cited by 2 •
2015
This protocol compares the relative affinities of binding partners for Rho-family GTPases, including Rac1. In vivo, Rac1-binding proteins compete for a single binding interface, the conformation of which is dictated by a bound nucleotide. The nucleotide is both important and difficult to control experimentally, due to the high hydrolysis rate.
15:27
Determination of High-affinity Antibody-antigen Binding Kinetics Using Four Biosensor Platforms
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Cited by 30 •
2017
We describe here protocols for the measurement of antibody-antigen binding affinity and kinetics using four commonly used biosensor platforms.
05:00
Fluorescence Anisotropy to Determine Transcription Factor-DNA Binding Affinity
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2025
This video describes high-performance fluorescence anisotropy that helps to monitor the interaction between transcription factors and DNA. The assay monitors the interactions of a fluorophore-labeled DNA molecule with its specific transcription factor by measuring the degree of polarization due to molecular rotation or anisotropy of the fluorophore-labeled DNA.
FAQs
Lower Kd values indicate tighter binding, but the number is meaningful only under the conditions used for the measurement. Comparing Kd values therefore requires attention to whether the interactions were assessed in comparable conditions. In biology, this helps distinguish stronger molecular recognition from an apparent difference caused by the measurement setting.
At equilibrium, the measured interaction reflects both complex formation and dissociation rather than either process alone. A system with substantial complex formation can still show a different affinity if dissociation changes the balance. This equilibrium perspective matters when interpreting protein-ligand or antibody-antigen recognition, because the affinity value summarizes the balance between bound and unbound states.
Interaction strength is represented by an affinity value such as Kd, whereas kinetics describes how quickly binding and dissociation occur, and thermodynamics describes features associated with the interaction. These measurements provide related but different perspectives. Considering them together can give a fuller biological interpretation than relying on affinity alone, particularly for molecular recognition.
These approaches can all support interaction analysis, but they may emphasize different aspects of the result. Surface plasmon resonance, isothermal titration calorimetry, and fluorescence-based assays can reveal interaction strength, while the broader measurement may also provide kinetic or thermodynamic information. Selecting among them depends on which features of the molecular interaction are most relevant.
A typical workflow begins by examining the interaction between the selected molecules under defined conditions, using an appropriate measurement method. The observed equilibrium between complex formation and dissociation is then used to obtain an affinity value such as Kd. The result can subsequently be interpreted alongside kinetic or thermodynamic information when the method provides it.
The measurement is useful when researchers need to connect molecular recognition with biological function. Applications include characterizing signaling pathways, examining antibody-antigen interactions, studying enzyme inhibitors, and evaluating potential drug candidates. In each case, the affinity result helps describe how strongly relevant molecules interact and supports comparisons among biological or candidate molecular interactions.