FAST Tag Reversible Chromophore Binding for Rapid Fluorescent Labeling
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Solution Overview
Problem
Current fluorescent protein-based probes for imaging in living cells face limitations such as slow maturation, oxygen dependency, photobleaching, and size-related functional perturbations, which hinder real-time observation of protein dynamics with high spatial and temporal resolution.
Innovation Solution
A functional derivative of Photoactive Yellow Protein (PYP) that binds reversibly to a fluorogenic chromophore, allowing for rapid fluorescence switching and enhanced photostability, with specific kinetic constants for binding and dissociation, enabling efficient and specific labeling of proteins without interfering with their function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GFP-like fluorescent proteins are used for labeling, then the fluorescence can be genetically encoded with absolute specificity, but the maturation process is slow (40 minutes to 2 hours) and requires molecular oxygen
Solution Approach 1:
The invention extracts the fluorophore synthesis function from the protein tag itself. Instead of the tag generating its own fluorophore through slow autocatalytic processes, the system uses a separate small-molecule fluorogenic probe that binds to the tag. This separates the genetic encoding function (which provides specificity) from the fluorophore generation function (which now occurs rapidly through probe binding), resolving the contradiction between specificity and maturation speed.
Solution Approach 2:
The invention introduces an intermediary small-molecule fluorogenic probe that acts as a mediator between the genetically encoded tag and the fluorescent signal. The tag serves as an anchor for the probe, while the probe provides the fluorophore function. This intermediary approach allows the system to benefit from both the genetic specificity of the tag and the rapid binding kinetics of the probe, avoiding the slow maturation and oxygen dependency of autocatalytic fluorophore generation.
2Reliability
If GFP-like fluorescent proteins are used, then the fluorophore is covalently formed within the protein, but the photostability is limited with half-times between 5 and 200 seconds
Solution Approach 1:
The invention changes the chemical nature of the fluorophore from a covalently bound protein-based chromophore to a non-covalently bound small-molecule fluorogenic probe. This parameter change in the fluorophore's chemical structure and binding mode fundamentally alters the photostability characteristics. The probe-based system achieves superior photostability because the probe can be replenished from the cellular pool after photobleaching, and the non-covalent binding allows for faster exchange kinetics that prevent permanent damage accumulation.
3Measurement precision
If the fluorescent tag is fused to the protein of interest, then specific labeling is achieved, but the tag may perturb the function, folding, or localization of the native protein
Solution Approach 1:
The invention extracts the fluorophore-generating capability from a large protein tag and replaces it with a minimal peptide-based binding domain. This dramatically reduces the size of the fusion tag (from 25-30 kDa for GFP to much smaller peptide sequences), minimizing the perturbation to the native protein's function, folding, and localization while retaining the ability to provide specific genetic encoding for targeted labeling.
4Illumination intensity
If organic fluorophores are used for fluorescence microscopy, then high brightness and specificity are achieved, but photobleaching occurs after a limited number of excitation-emission cycles
Solution Approach 1:
The invention implements a discard-and-recover mechanism for the fluorophore. When the fluorogenic probe bound to the tag undergoes photobleaching, it is discarded (loses its fluorescent capability). However, the tag remains intact and can rapidly bind a fresh probe from the cellular pool, effectively recovering the fluorescent signal. This continuous renewal process eliminates the permanent signal loss that occurs with covalently attached fluorophores, enabling long-term observation while maintaining high brightness.
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 solution provides a tunable and highly dynamic fluorescent labeling system that overcomes the limitations of existing probes, allowing for real-time imaging with reduced photobleaching and minimal functional disruption, enabling multiplexing and efficient protein tracking in various biological systems.
Implementation Method 1
binds reversibly a fluorogenic chromophore
Implementation Method 2
fluorescent labeling system that overcomes the limitations of existing probes
Implementation Method 3
capable of enhancing the brightness of the said fluorogenic chromophore upon complexation
Implementation Method 4
inducing the spectral shift of the said fluorogenic chromophore through the ionization of an auxochromic group thereof
Implementation Method 5
inducing the spectral shift of the said fluorogenic chromophore through the ionization of an auxochromic group
Data Source
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Figure 5
AI summary
The present invention relates to a functional derivative of a Photoactive Yellow Protein (PYP), or a functional fragment thereof, for fluorescently labelling particles, e.g. proteins, or surfaces, which is capable of binding reversibly a fluorogenic chromophore of formula (I), and which is capable of enhancing the brightness of the said fluorogenic chromophore upon complexation thereto; and of inducing the spectral shift of the said fluorogenic chromophore through the ionization of an auxochromic group thereof.