Ultrafast memory loss and relaxation processes in hydrogen-bonded systems

Area of Science:

• Physical Chemistry
• Biophysics
• Spectroscopy

Background:

• Hydrogen bond dynamics are crucial for the structural memory of aqueous systems, including water and biomolecules.
• Understanding these dynamics in real-time is essential for molecular interactions in biological and chemical environments.

Purpose of the Study:

• To investigate the real-time structural dynamics and hydrogen bond behavior in neat water and DNA hydration shells using femtosecond vibrational spectroscopy.
• To elucidate the role of hydration shells as energy sinks in aqueous systems.

Main Methods:

• Femtosecond (fs) time-domain vibrational spectroscopy was employed to monitor ultrafast structural dynamics.
• Analysis focused on OH stretching and bending excitations in water molecules and hydrogen bond rearrangements in DNA hydration shells.

Main Results:

• Neat liquid water exhibits ultrafast loss of structural memory, with correlations decaying in under 100 fs.
• Water molecule excitations decayed on a subpicosecond timescale, followed by hydrogen bond network energy dissipation within picoseconds.
• DNA hydration shells showed similar, slightly slower dynamics, with strong phosphate-water coupling and subpicosecond hydrogen bond rearrangement.

Conclusions:

• Hydration shells act as primary heat sinks, efficiently dissipating excess energy.
• Femtosecond spectroscopy provides critical insights into the ultrafast dynamics governing aqueous system structure and function.
• The study highlights the dynamic nature of water-biomolecule interactions and their role in energy management.