Protein Binding Assay
Protein Binding Assay - Related Videos
07:53
Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin
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Cited by 18 •
2008
Proteins bind to filamentous actin (F-actin) through distinct actin binding modules. In this video we demonstrate the procedure of actin co-sedimentation, which is an in vitro assay routinely used to analyze proteins or specific domains that bind F-actin.
04:05
Competition Binding Assay to Study Competing GTPase-Binding Protein Partners
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2025
This video demonstrates a competition assay to study GTPase-binding protein partners. Utilizing nucleotide-bound GTPase protein immobilized on magnetic beads, the competitive binding between two interacting protein partners for the same binding site on the GTPase can be studied to assess the binding affinities of the protein partners.
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.
05:07
RNA-Protein Pull-Down Assay to Isolate RNA-Binding Proteins via Affinity Extraction
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2025
This video demonstrates an in vitro RNA pull-down assay to identify RNA-binding proteins (RBPs), which interact with the adenylate-uridylate-rich element (ARE) sequences in mRNA. The target RBPs from a cell lysate are mixed with an RNA probe to form RNA-protein complexes. The complexes are isolated via affinity purification utilizing the affinity of the desthiobiotin label of the RNA probe to a streptavidin-labeled magnetic bead.
06:30
SELEX-Based In Vitro Binding Assay to Identify RNA-Protein Interactions
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2025
In this video, we describe the systematic evolution of ligands by the exponential enrichment (SELEX) method to identify specific RNA-binding sequences for a target protein of interest. The protein is incubated with a large pool of randomized RNA sequences, and the protein-binding RNA sequences are isolated, PCR-amplified, and sequenced to identify their protein-binding sites.
FAQs
Interaction strength is inferred from how much of a test molecule associates with the protein under controlled conditions. Measurements across a range of concentrations produce a binding curve, whose shape supports estimation of affinity and the dissociation constant. Comparing these values helps determine whether one ligand binds more strongly than another and provides quantitative evidence for molecular recognition.
Specificity is examined by comparing the protein’s interaction with different molecules, including competing ligands. If one molecule changes the measured binding of another, the results can reveal competition for interaction with the protein. This approach helps researchers compare candidate ligands and determine whether molecular recognition favors a particular substrate, antibody, drug, or related compound.
Separation-based assays quantify binding by distinguishing molecules associated with the protein from those remaining free. Signal-based assays instead detect a binding-dependent change through fluorescence, absorbance, or radioactivity. Both formats can generate quantitative binding data, but they differ in how the bound fraction is identified and measured under the assay’s controlled experimental conditions.
A typical workflow combines the protein and test molecule under controlled conditions, allows the interaction to occur, and then measures the resulting binding. Depending on the assay design, researchers either separate bound from free molecules or detect a binding-dependent signal. Repeating measurements across relevant concentrations enables construction of a binding curve for quantitative analysis.
Binding curves show how the measured interaction changes as the concentration of a test molecule varies. Analysis of these curves can estimate affinity and dissociation constants, which summarize the strength of the interaction. Researchers can then compare ligands quantitatively rather than relying only on whether binding is detectable, supporting conclusions about relative molecular recognition.
These assays support studies of protein function by measuring interactions with substrates, antibodies, drugs, or other ligands. In biology, the results help investigate molecular recognition and interactions that regulate cellular processes. In therapeutic research, the same measurements can compare candidate compounds and provide quantitative evidence for evaluating their interactions with a target protein.