Slow relaxation process in DNA at different levels of hydration

Area of Science:

• Biophysics
• Materials Science
• Structural Biology

Background:

• Hydrated biopolymers exhibit a dynamic transition around 200-230 K, characterized by increased atomic motion.
• The precise nature and underlying mechanisms of this transition remain unclear.
• This transition is hypothesized to be critical for the biological functions of these macromolecules.

Purpose of the Study:

• To elucidate the nature of the dynamic transition in hydrated deoxyribonucleic acid (DNA).
• To investigate the role of hydration level on the observed dynamic transition.
• To explore the relationship between water dynamics and the biopolymer transition.

Main Methods:

• Inelastic neutron scattering (INS) was employed to probe atomic dynamics.
• Experiments were conducted on hydrated DNA samples at varying hydration levels.
• The study focused on analyzing atomic mean-squared displacements and relaxation processes.

Main Results:

• The dynamic transition in DNA is associated with the emergence of a slow relaxation process.
• Decreasing the hydration level significantly suppresses both the slow relaxation and the dynamic transition.
• Reduced water content dynamically mimics a decrease in temperature.

Conclusions:

• The dynamic transition in hydrated DNA is mediated by the water of hydration.
• The findings support the hypothesis that water dynamics are essential for the observed biopolymer transition.
• Bulk water exhibits a similar dynamic transition around the same temperature range, reinforcing the role of hydration.