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Ultrafast Two-Dimensional Infrared Spectroscopy and Molecular Dynamics Simulations Reveal Slow Water Dynamics in
Aruna K Mora1,2, Dibyendu Bandyopadhyay3, Niharendu Choudhury2,4
1Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, INDIA.
The Journal of Physical Chemistry. B
|July 15, 2025
Summary
We used ultrafast 2D infrared spectroscopy and a novel vibrational reporter to study water dynamics inside cyclodextrin cavities. This revealed a rigid, confined hydration environment caused by steric confinement, not polar interactions.
Area of Science:
- Supramolecular Chemistry
- Biophysical Chemistry
- Spectroscopy
Background:
- Cyclodextrins are crucial in supramolecular chemistry and drug delivery.
- Internal water dynamics in cyclodextrins were previously unstudied with ultrafast spectroscopy.
- A suitable vibrational reporter was needed to probe these dynamics.
Purpose of the Study:
- To apply two-dimensional infrared (2DIR) spectroscopy to investigate water dynamics within a cyclodextrin cavity.
- To utilize azidoadamantane (AdN3) as a vibrational reporter for host-guest complexes.
- To understand the influence of nanoconfinement on water behavior.
Main Methods:
- Employed two-dimensional infrared (2DIR) spectroscopy.
- Used azidoadamantane (AdN3) as a vibrational reporter for sulfobutylether-β-cyclodextrin (SBE-β-CD).
- Performed frequency-frequency correlation function (FFCF) analysis and molecular dynamics simulations.
Main Results:
- Observed minimal spectral diffusion and strong vibrational frequency correlation.
- Detected extended water residence times, indicating a rigid, nanoconfined hydration environment.
- Identified steric confinement by the host cavity as the cause of slowed water dynamics.
Conclusions:
- 2DIR spectroscopy can probe ultrafast hydration dynamics in nanoscale cavities.
- Steric confinement within cyclodextrins significantly restricts water mobility.
- Findings have implications for drug delivery, molecular recognition, and understanding confined water systems.
