Ligand Binding Assay Using Thermal Denaturation and Chimeric Proteins
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Solution Overview
Problem
Current ligand binding assays face challenges such as fluorescence interference, high costs, and safety hazards, particularly in thermal shift assays that require centrifugation and are not suitable for highly inhomogeneous proteins or those that do not promote aggregation upon ligand binding.
Innovation Solution
A method involving a fluid mixture of intact viable cells expressing a chimeric protein with a target macromolecule linked to a labeling peptide, where the mixture is heated to denature proteins not bound to a compound, and a second label reacts with the labeling peptide to form a detectable signal, indicating binding between the compound and the target macromolecule, without the need for centrifugation or filtration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal shift assay is used to measure ligand binding, then binding detection is achieved, but centrifugation and oil dispensing steps are required which reduce assay simplicity and throughput
Solution Approach 1:
The invention extracts and eliminates the centrifugation and oil dispensing steps from the thermal shift assay procedure. By using a closed-well format with volatile oil that forms a seal without requiring centrifugation, the complex separation and preparation steps are removed while maintaining the essential binding detection capability.
Solution Approach 2:
The invention introduces volatile oil as an intermediary substance that serves multiple functions: it creates a seal between the plate and lid without requiring centrifugation, prevents evaporation during heating, and allows for simple plate sealing. This intermediary eliminates the need for complex centrifugation-based sealing methods.
2Measurement precision
If fluorescent labeling is used in binding assays, then binding detection sensitivity is improved, but fluorescence interference alters binding characteristics
Solution Approach 1:
The invention replaces persistent fluorescent labels with a disposable thermal denaturation readout method. The binding detection is achieved through the thermal stability change of the protein-ligand complex itself, which is then detected by a subsequent denaturation assay. This eliminates the need for fluorescent labels that can interfere with binding while maintaining detection sensitivity.
Solution Approach 2:
The invention substitutes the optical detection system (fluorescence) with a thermal-mechanical system. Instead of using fluorescent labels and optical detectors, the assay uses thermal denaturation and aggregation detection, replacing the mechanical/optical measurement approach while maintaining the ability to detect binding events with high sensitivity.
3Measurement precision
If radioactively labeled binding assay is used for membrane targets, then binding detection is achieved, but high cost and safety hazards restrict laboratory use
Solution Approach 1:
The invention replaces expensive and hazardous radioactive labels with a disposable thermal denaturation readout system. The binding information is captured through the thermal stability change of the complex, which is then detected by a subsequent heating and aggregation detection step. This eliminates radioactive materials entirely while maintaining binding detection capability at lower cost and without safety hazards.
Solution Approach 2:
The invention introduces thermal denaturation as an intermediary detection step that bridges ligand binding and signal detection. Instead of directly detecting radioactive or fluorescent labels, the assay uses thermal stability as an intermediary property that reflects binding status, then detects this through aggregation or other readout methods, eliminating the need for hazardous labels.
4Loss of information
If NMR based analysis is used for structure-based drug design, then detailed protein structure information is obtained, but high cost and long analysis time reduce efficiency
Solution Approach 1:
The invention applies partial thermal denaturation rather than complete structural analysis. By using a simplified thermal shift assay that measures only the melting temperature change upon ligand binding, the method obtains sufficient binding information without the exhaustive structural detail of NMR, achieving a favorable balance between information quality and analysis speed.
Solution Approach 2:
The invention replaces the expensive and time-consuming NMR instrumentation and analysis with a simple, rapid thermal denaturation assay. The binding information is obtained through a quick heating process followed by aggregation detection, providing sufficient structure-based drug design information at a fraction of the cost and time of NMR analysis.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides a sensitive, precise, and homogeneous assay for measuring ligand-protein interactions, allowing for the detection of binding without separation steps and is applicable to a wide range of proteins, including those that do not aggregate upon ligand binding, enhancing assay throughput and sensitivity.
Implementation Method 1
heating the fluid mixture of step (a) under conditions that cause denaturation of chimeric molecules not bound to the compound
Implementation Method 2
contacting the combined mixture of step (c) with a second label that binds to the labeling peptide to form a complex
Data Source
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AI summary
Disclosed are methods for detecting and quantitatively measuring a binding property of a compound to a target macromolecule, wherein the target macromolecule is subject to denaturation and is linked to a labeling peptide, such as a short enzyme fragment. The method uses a fluid mixture comprising (i) a chimeric molecule comprising a target macromolecule linked to the labeling peptide, wherein the target macromolecule may be a chimeric protein expressed by and within an intact viable cell and (ii) a compound being measured for binding to the target macromolecule, wherein said target macromolecule is subject to denaturation. After allowing for binding of the compound (e.g. a small molecule inhibitor of the target macromolecule), one detects a signal from the labeling peptide, such as by enzyme fragment complementation. This signal indicates a differential between denatured and non-denatured target macromolecules and thereby indicates a differential between target macromolecules not bound to the compound and target macromolecules bound to the compound, respectively.