Dynamic Covalent Programming at DNA Base-Pairing Interfaces

Area of Science:

• Chemical Biology
• Nucleic Acid Chemistry
• Biophysical Chemistry

Background:

• Fluorescent nucleobase analogues (FBAs) are valuable tools for studying nucleic acid structure and dynamics.
• Existing methods for programming FBA function at DNA's hydrogen-bonding interface are limited.
• Controlling FBA behavior requires precise chemical modifications compatible with DNA synthesis.

Purpose of the Study:

• To introduce a novel nucleobase design strategy for conformational programming within DNA.
• To create a library of hydrazone nucleobases with tunable optical and conformational properties.
• To explore the use of these modified nucleobases for real-time monitoring and sensing applications.

Main Methods:

• Site-specific incorporation of a 6-amino adenine analogue (^hzA) using phosphoramidite chemistry.
• Post-synthetic condensation with various aldehydes to generate diverse hydrazone nucleobases.
• Characterization of photophysical properties (brightness, quantum yield, excitation/emission maxima) and kinetic/thermodynamic analyses in different DNA structures (ssDNA, duplex DNA).

Main Results:

• Generated exceptionally bright FBAs with tunable properties, including a coumarin-derived system with >120-fold fluorescence enhancement.
• Demonstrated that DNA structure dictates hydrazone formation rates and product stability, with ssDNA favoring rapid formation and high stability.
• Developed a specific hydrazone analogue (^CySalA) that selectively pairs with thymidine and exhibits distinct responses to metal ions and base-pairing mismatches.

Conclusions:

• Established a versatile hydrazone-based platform for programming functional states at DNA's hydrogen-bonding interface.
• Transformed a native hydrogen-bonding face into a modular chemical handle for fine-tuning DNA structure, reactivity, and optical responses.
• This approach enables advanced applications in real-time DNA monitoring, structural studies, and molecular sensing.