Tricyclic Cytidine Fluorescent Probe for Duplex Sensing
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Solution Overview
Problem
Current fluorescent nucleobase analogues are either quenched when base stacked or emit only at wavelengths less than 525 nm, and there is a lack of nucleoside analogues that significantly increase fluorescence upon duplex formation, limiting their application in turn-on fluorescence sensing for DNA and RNA synthesis and strand hybridization.
Innovation Solution
Design and synthesis of tricyclic cytidine compounds, such as 8-diethylamino-tC (8-DEA-tC), which exhibit a 20-fold increase in fluorescent quantum yield upon duplex formation, dependent on neighboring bases, and are virtually non-fluorescent as a free nucleoside, enabling sequence-specific detection of DNA and RNA duplexes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If fluorescent nucleobase analogues are designed to emit at wavelengths greater than 525 nm, then the emission wavelength is improved, but the fluorescence intensity is quenched when base stacked
Solution Approach 1:
The patent modifies the chemical structure of nucleobase analogues by introducing specific substituents and ring systems that change the photophysical parameters, enabling long-wavelength emission (>525 nm) while maintaining fluorescence intensity through controlled base stacking interactions
Solution Approach 2:
The invention creates composite nucleobase structures combining multiple functional groups and ring systems that work together to achieve both long-wavelength emission and resistance to quenching, forming a composite material with optimized photophysical properties
2Measurement precision
If nucleoside analogues are designed to be fluorescent as free nucleosides, then the fluorescence detection sensitivity is improved, but the turn-on response upon duplex formation is reduced
Solution Approach 1:
The patent designs nucleoside analogues that are deliberately kept non-fluorescent in the free state by incorporating quenching moieties or restricting conformations, then achieves turn-on fluorescence upon duplex formation where the complementary base pairing protects against quenching or activates emission
Solution Approach 2:
Instead of making free nucleosides fluorescent and relying on quenching upon binding, the invention inverts the approach by making free nucleosides non-fluorescent and achieving fluorescence activation upon duplex formation, thereby enhancing turn-on response
3Ease of operation
If conventional fluorescent probes are used for DNA and RNA detection, then the detection capability is achieved, but the sequence-specificity and sensitivity are limited
Solution Approach 1:
The patent incorporates fluorescent nucleobase analogues directly into the DNA or RNA sequence themselves, allowing the nucleic acid to serve its own detection function through intrinsic fluorescence properties that are activated or modulated by specific base pairing, eliminating the need for separate probe molecules
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
The 8-DEA-tC compound provides a robust and sequence-specific fluorescence turn-on response, enhancing the sensitivity and specificity of DNA and RNA detection, suitable for enzymatic synthesis monitoring and strand hybridization analysis.
Implementation Method 1
exhibit a 20-fold increase in fluorescent quantum yield upon duplex formation
Implementation Method 2
Kinetic isotope effects from the use of deuterated buffer show that the duplex protects 8-DEA-tC against quenching by excited state proton transfer
Data Source
AI summary
Herein reported are new tricyclic cytidine compounds, such as 8-diethylamino-tC (8-DEA-tC), that respond to DNA and/or RNA duplex formation with up to a 20-fold increase in fluorescent quantum yield as compared with the free nucleoside, depending on neighboring bases. This turn-on response to duplex formation is by far the greatest of any reported nucleoside analogue that can participate in Watson-Crick base pairing. Measurements of the quantum yield of 8-DEA-tC mispaired with adenosine and, separately, opposite an abasic site show that there is almost no fluorescence increase without the formation of correct Watson-Crick hydrogen bonds. Kinetic isotope effects from the use of deuterated buffer show that the duplex protects 8-DEA-tC against quenching by excited state proton transfer. DFT calculations provide a rationale for the observed photophysical properties that is dependent on duplex integrity and the electronic structure of the analogue.