Membrane Protein Ligand Binding Assays

Elevate your protein research with Eurofins CALIXAR's advanced ligand binding assays, featuring MicroScale Thermophoresis, radioligand binding, and fluorescence polarization. Our cutting-edge technologies ensure precise insights into protein interactions for (bio)drug discovery, pharmaceuticals, and biotechnology. Benefit from fully native proteins, high-quality processes, and tailored deliverables with Eurofins CALIXAR. Explore Ligand Binding Assay services today.

Ligand Binding Assays play a pivotal role in deciphering the intricate dance of proteins and ligands within biological systems. These assays are designed to investigate and quantify the binding interactions between a target protein, referred to as the receptor, and a ligand—a molecule that binds to the receptor with specificity. The goal is to gain a comprehensive understanding of the kinetics, affinity, and specificity of these interactions.

Utilizing various techniques such as MicroScale Thermophoresis, Radioligand Binding, and Fluorescence Polarization, Ligand Binding Assays offer a window into the molecular intricacies governing biological and chemical processes. Whether applied to (bio)drug discovery, pharmaceuticals, or biotechnology, these assays provide invaluable insights, guiding researchers in optimizing the design and functionality of proteins for diverse applications.

Techniques in Ligand Binding Assays

MicroScale Thermophoresis

MicroScale Thermophoresis (MST) is a powerful technique employed in ligand binding assays to unravel the intricacies of protein interactions. This method utilizes microscopic temperature gradients to quantify the movement of molecules in a solution, enabling the determination of binding parameters without the need for immobilization. The Isothermal Spectral Shift detection further enhances accuracy, making MST an invaluable tool for studying ligand-protein interactions with precision.

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Radioligand Binding Assay

Radioligand Binding Assay is a classic, yet highly effective technique for probing ligand-receptor interactions. In this method, a radiolabeled ligand competes with an unlabeled ligand for binding sites on a target receptor. By measuring the radioactivity associated with the bound ligand, researchers gain quantitative insights into the affinity and specificity of the ligand-receptor interaction, providing critical data for drug development and small molecular discovery.

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Fluorescence Polarization

Fluorescence Polarization is an innovative technique that exploits the changes in polarized light upon ligand binding to a fluorescently labeled molecule. This assay measures the rotational motion of fluorophores, providing precise information about the size and shape of molecular complexes. Widely used in ligand binding assays, Fluorescence Polarization offers high sensitivity and accuracy in determining binding affinities and studying molecular interactions.

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Enzymatic Assays

Enzymatic Assays focus on the catalytic activity of enzymes and their interaction with ligands. By measuring the rate of enzymatic reactions or substrate conversion, researchers can assess the effects of various ligands on enzyme activity. These assays are fundamental in drug discovery, where understanding the interactions between ligands and enzymes is critical for developing targeted therapies and optimizing pharmaceutical compounds.

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MicroScale Thermophoresis (MST): Precise Molecular Interactions

What is MicroScale Thermophoresis (MST)?

MicroScale Thermophoresis (MST) is a cutting-edge biophysical technique used to study molecular interactions, particularly in the field of ligand-receptor interactions. The method relies on the movement of molecules in a temperature gradient, allowing precise measurement of their thermophoretic mobility. In MST, one of the interacting partners, either the ligand or the receptor, is fluorescently labeled.

How does it work?

  • Fluorescent Labeling: The ligand or receptor is labeled with a fluorophore, and the interaction is monitored by tracking the movement of the fluorescent molecule.
  • Microscale Temperature Gradients: A microscopic temperature gradient is induced in a capillary, creating a local temperature difference. The molecules in the sample solution move in response to this gradient.
  • Quantitative Analysis: The change in fluorescence signal is quantified, providing information about the strength and dynamics of the interaction. The technique allows researchers to determine binding affinities, kinetics, and stoichiometry.

What is Isothermal Spectral Shift?

Isothermal Spectral Shift is a detection method used in MicroScale Thermophoresis (MST) experiments. In MST, the interaction between molecules is assessed by monitoring the movement of fluorescently labeled molecules in response to a microscopic temperature gradient. Isothermal Spectral Shift specifically refers to the measurement of changes in the fluorescence spectrum of a labeled molecule at a constant temperature, providing insights into binding events and molecular interactions. At Eurofins CALIXAR, we apply Monolith series of instruments developed by Nanotemper Technologies, called Monolith X (Nanotemper). These instruments, such as Monolith NT.115 and Monolith NT.LabelFree, are designed to precisely control the temperature gradient in the capillary during MST experiments. Monolith X is equipped with advanced features, including red fluorescence and Isothermal Spectral Shift detection, allowing for highly accurate and sensitive analysis of molecular interactions without the need for immobilization. It is widely utilized in the study of ligand-receptor interactions, protein-protein interactions, and other biomolecular interactions in research and drug discovery.



  • Red fluorescence
  • Spectral Shift

Dynamic range:

  • 1nm to mM

Detected molecule range:

  • 101 – 107 Daltons

Samples per run:

  • Up to 24

Radioligand Binding Assay: decoding molecular affinities

What is Radioligand Binding Assay?

Radioligand Binding Assayis a powerful technique used to study the interaction between a ligand, typically a small molecule or drug, and its specific binding site on a receptor. This method involves labeling the ligand with a radioactive isotope, allowing for highly sensitive detection and quantification of binding events. Radioligand binding assays are widely employed in pharmacology, drug development, and molecular biology to understand the affinity, specificity, and kinetics of ligand-receptor interactions.

How does it work?

  1. Radiolabeling the Ligand: The ligand of interest is tagged with a radioactive isotope, often tritium (3H) or iodine-125 (125I). This radiolabeling allows researchers to trace and quantify the binding of the ligand to its receptor.
  2. Preparing the Receptor: The receptor, typically a protein or cell membrane, is prepared for the assay. It may involve isolating the receptor from cells or tissues or utilizing recombinant proteins.
  3. Incubation with Radiolabeled Ligand: The radiolabeled ligand is then incubated with the prepared receptor. During this step, the ligand competes with non-labeled ligands for binding sites on the receptor.
  4. Separation of Bound and Free Ligands: After incubation, the mixture is separated into bound and free fractions. Techniques like filtration or centrifugation are commonly employed to achieve this separation.
  5. Quantification of Binding: The amount of radiolabeled ligand bound to the receptor is quantified using a scintillation counter or a gamma counter. This provides a measure of the specific binding affinity between the ligand and the receptor.
  6. Data Analysis: The collected data is analyzed to determine various parameters, including binding affinity (KD), the number of binding sites, and the kinetics of the interaction.

Radioligand binding assays are invaluable in drug discovery and pharmacological research, providing precise insights into the molecular interactions that govern the efficacy and specificity of potential therapeutic targets.

Fluorescence polarization: illuminating molecular interactions

What is fluorescence polarization?

Fluorescence polarization is a sophisticated technique employed to investigate molecular interactions, particularly in the realm of ligand-receptor binding. This method leverages the principles of light polarization to elucidate the dynamics of molecular complexes. By utilizing fluorescently labeled molecules, researchers can gain detailed insights into the size, shape, and interactions of biomolecules.

How does it work?

  1. Fluorescent Labeling: The molecule of interest, often a ligand or protein, is labeled with a fluorophore. This fluorescent tag serves as a probe for studying molecular interactions.
  2. Polarized Light Excitation: Polarized light is used to excite the fluorophores in the labeled molecules. The emitted fluorescence is also polarized, and its orientation is influenced by the rotational motion of the labeled molecules.
  3. Measurement of Fluorescence Polarization: The degree of polarization of the emitted fluorescence is measured. This is influenced by the size and shape of the fluorescently labeled molecules and their interactions with other molecules.
  4. Changes in Polarization: When the labeled molecules bind to other molecules, such as ligands binding to receptors, the rotational motion is restricted, leading to changes in fluorescence polarization. These changes serve as indicators of molecular interactions.
  5. Quantification of Binding: The alterations in fluorescence polarization are quantified, providing a quantitative measure of the binding affinity and kinetics between the labeled molecule and its interacting partner.
  6. Data Analysis: The collected data is analyzed to derive essential information, including binding constants, stoichiometry, and the nature of molecular interactions.

Fluorescence polarization assays are pivotal in drug discovery, molecular pharmacology, and studying protein-protein interactions. This technique, offering high sensitivity and accuracy, enables researchers to unravel the intricacies of molecular dynamics, contributing to advancements in various scientific domains.

Enzymatic assays: deciphering catalytic activities

What are enzymatic assays?

Enzymatic assays are powerful techniques used to measure the catalytic activity of enzymes or the impact of various factors on enzymatic reactions. These assays play a pivotal role in understanding the kinetics, substrate specificity, and inhibition of enzymes, crucial for drug discovery, diagnostics, and biochemical research. Examples include ELISA (Enzyme-Linked Immunosorbent Assay) and various immunoassays, which utilize enzyme-linked reactions for sensitive detection.

How does it work?

  1. Enzyme Preparation: The enzyme of interest is isolated, purified, or synthesized for the assay. This may involve extracting enzymes from tissues, cells, or employing recombinant DNA technology.
  2. Substrate Interaction: The enzyme is incubated with its substrate, and the enzymatic reaction is initiated. The substrate is the molecule upon which the enzyme acts to produce a product.
  3. Detection Method: In immunoassays like ELISA, an enzyme is linked to an antibody or antigen, and its activity is harnessed for the detection of specific molecules. The enzymatic reaction produces a measurable signal, often a color change or luminescence.
  4. Signal Measurement: The generated signal is quantified using specialized instruments such as a spectrophotometer or a luminometer. The intensity of the signal corresponds to the concentration of the analyte or the enzymatic activity.
  5. Calibration and Data Analysis: Standard curves or controls are used for calibration, and the collected data is analyzed to determine enzyme activity, substrate concentrations, or the presence of specific analytes.

Enzymatic assays are instrumental in drug development, where understanding enzyme behavior aids in designing targeted therapies. In diagnostics, immunoassays provide sensitive and specific detection of biomarkers for diseases. Immunoassays stand as pillars in life sciences, offering a versatile toolkit for researchers and clinicians to explore the intricate world of enzyme interactions and biomolecular detection.

Elevate your research with Eurofins CALIXAR's high quality custom proteins

Our Ligand Binding Assays provide an unparalleled window into the world of molecular interactions. From the high-throughput capabilities of MicroScale Thermophoresis to the sensitivity of Radioligand Binding and the precision of Fluorescence Polarization, we empower scientists and researchers in (bio)drug discovery, pharmaceuticals, biotechnology, and academia.

Partner with Eurofins CALIXAR for ligand binding assays that transcend expectations, combining innovation with reliability to unlock the full potential of your research.

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