Hydration of [d(CGC)r(aaa)d(TTTGCG)](2)

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• DNA.RNA hybrids are crucial in biological processes and therapeutics.
• Understanding their hydration and dynamics is key to elucidating their function and recognition.
• Chimeric duplexes, combining DNA and RNA, present unique structural features.

Purpose of the Study:

• To investigate the hydration and dynamics of RNA C2'-hydroxyl (OH) groups in a specific DNA.RNA hybrid chimeric duplex.
• To correlate structural conformations with observed hydration patterns.
• To elucidate the molecular basis for DNA.RNA hybrid recognition.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was used to study the hydration and dynamics.
• Analysis of Nuclear Overhauser Effect (NOE) cross-peak patterns provided structural information.
• Correlation times (tau(c)) of water molecules were determined.

Main Results:

• Long-lived water molecules were identified near RNA adenine protons and a specific DNA thymine (7T) in the RNA-DNA junction.
• DNA residue 7T exhibited an intermediate sugar conformation (O4'-endo), unlike other DNA residues.
• RNA C2'-OH groups oriented towards the 3'-phosphate, potentially forming hydrogen bonds, with slow exchange rates (5-20 s(-1)).

Conclusions:

• Distinct hydration patterns and RNA C2'-OH dynamics in the DNA.RNA hybrid suggest specific molecular interactions.
• The narrow minor groove may trap water, restricting hydroxyl proton dynamics.
• These findings provide a molecular foundation for understanding DNA.RNA hybrid structures and recognition mechanisms.