NTA Probe Detection of His-Tagged Proteins in PAGE
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Solution Overview
Problem
Current methods for detecting His-tagged proteins using metal ion-chelating nitrilotriacetate (NTA) moieties in polyacrylamide gel electrophoresis (PAGE) lack sensitivity and require specialized equipment, limiting their application and detection limits.
Innovation Solution
The use of fluorescently labeled NTA probes loaded with metal ions such as Ni2+, Zn2+, Cu2+, Cd2+, Hg2+, Co2+, and Fe2+, which are excited by UV light and emit visible fluorescence, allowing for detection of His-tagged proteins in PAGE or on blot membranes using a UV transilluminator and naked eye or bench camera visualization, with detection limits as low as 0.1 pmol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluorescently labeled NTA probes with visible emission are used, then detection sensitivity is improved, but specialized equipment requirements increase
Solution Approach 1:
The patent replaces complex antibody-based immunodetection systems with a simpler metal ion-chelating NTA probe system. The NTA probes use metal ion coordination chemistry to bind His-tagged proteins, and the fluorescent labels provide direct detection without requiring secondary antibodies or complex immunological reagents. This substitution maintains high detection sensitivity while reducing equipment and procedural complexity.
Solution Approach 2:
The patent employs multivalent chelator heads (MCHs) with multiple NTA moieties that increase metal ion loading capacity and enhance affinity for His6-tags by 1000-fold compared to monovalent NTA. This parameter change in the probe structure (from monoNTA to MCH-NTA) dramatically improves detection sensitivity while the use of UV-excitable fluorophores with visible emission simplifies the detection equipment needed.
2Measurement precision
If multivalent chelator heads are used to increase affinity, then detection sensitivity is improved, but probe complexity increases
Solution Approach 1:
The multivalent chelator heads are constructed by segmenting the probe into distinct functional modules: multiple NTA chelating moieties attached to a central core structure, with fluorescent labels positioned at appropriate distances. This segmentation allows each NTA unit to independently contribute to metal ion binding while the modular structure simplifies synthesis and characterization compared to completely novel complex structures.
Solution Approach 2:
The patent uses metal ions (Ni2+, Zn2+, Cu2+, etc.) as intermediaries that bridge the NTA chelator heads and the His-tagged proteins. The metal ion-loaded NTA probes act as intermediary complexes that provide both the affinity function (through metal-His interaction) and the detection function (through fluorophore emission), eliminating the need for direct conjugation of large antibody molecules to the probe structure.
3Quantity of substance
If antibody-based immunoblotting is replaced with NTA probes, then cost is reduced, but detection limit may worsen
Solution Approach 1:
The patent creates composite probe structures by combining metal ion-chelating NTA moieties with fluorescent labels. This composite material integrates the affinity-capture function of metal chelation with the detection function of fluorescence, providing a cost-effective alternative to antibodies while achieving comparable or superior detection limits through the enhanced affinity of multivalent chelator heads.
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 enhances protein detection sensitivity and simplicity, enabling visualization of as low as 0.1 pmol of His6-tagged proteins in SDS-PAGE and 2.5 pmol on blot membranes without the need for antibody-based immunoblotting, using commercially available reagents and straightforward protocols.
Implementation Method 1
using a fluorescently labeled NTA probe loaded with a metal ion such as Ni2+, Zn2+, Cu2+, Cd2+, Hg2+, Co2+, and Fe2+ that is excited by UV light and emits visible fluorescence
Implementation Method 2
metal ion-chelating nitrilotriacetate (NTA) moiety
Implementation Method 3
exposing the gel following separation of the proteins in the sample using PAGE, to a UV-light source
Implementation Method 4
separation of the proteins in the sample using PAGE
Data Source
AI summary
Methods for detecting His-tagged proteins using metal ion-chelating nitrilotriacetate (NTA) probes and polyacrylamide gel electrophoresis (PAGE) are disclosed. In one embodiment, the method includes using a metal ion-loaded NTA probe coupled to a UV-excitable fluorophore with visible emission and the presence of His-tagged proteins in the sample is determined by exposing the gel following PAGE, to a UV-light source with naked human eye or bench camera visualization. The metal ion-loaded NTA-containing chelator head can be coupled to a fluorophore that is not UV-excitable (i.e., with the majority of emission and excitation in the visible region of the electromagnetic spectrum. The method includes separating proteins in a sample using PAGE, contacting the gel following electrophoresis with a composition containing a metal ion-loaded NTA probe coupled to the fluorophore, to allow binding of the probe to the His-tagged proteins, and detecting the presence of the probe and therefore of the His-tagged proteins.