Dynamics in synthetic oligonucleotides. A solid-state deuterium NMR study.

Area of Science:

• Biophysics
• Structural Biology
• Nuclear Magnetic Resonance Spectroscopy

Background:

• Deoxyribonucleic acid (DNA) dynamics are crucial for its biological functions.
• Understanding DNA dynamics requires investigating molecular motion at various hydration levels.
• Solid-state NMR is a powerful technique for probing molecular dynamics in complex systems.

Purpose of the Study:

• To investigate the effect of hydration on the dynamics of a specific DNA oligonucleotide, [d(CGCGAAT*T*CGCG)]2.
• To characterize base motion and helical axis motion as a function of water content.
• To correlate observed dynamics with changes in DNA structure.

Main Methods:

• Solid-state 2H Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
• Quadrupole echo line shapes, spin-lattice relaxation, and quadrupolar echo decay rates were measured.
• Experiments were conducted across a range of hydration levels (W = 0 to ~30).
• [methyl-2H]thymidine labeling was used for spectral analysis.

Main Results:

• Base motion, modeled as libration or diffusion in a cone, slightly increased with hydration.
• A slower component of motion around the helix axis emerged at W ≈ 10.
• This slower motion increased in rate and amplitude with further hydration, leading to observed line shape changes at W ≈ 21.

Conclusions:

• Hydration significantly influences the dynamic behavior of DNA oligonucleotides.
• Water molecules play a critical role in modulating both base and helical axis motions.
• These hydration-dependent dynamics are essential for understanding DNA's structural flexibility and function.