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Water in channel-like cavities: structure and dynamics
M S Sansom1, I D Kerr, J Breed
1Laboratory of Molecular Biophysics, University of Oxford, United Kingdom. mark@biop.ox.ac.uk
Biophysical Journal
|February 1, 1996
Summary
Water molecules inside ion channels form ordered shells, affecting their structure and dynamics. Confined water shows reduced mobility in narrow channels, impacting the local dielectric constant.
Area of Science:
- Biophysics
- Computational Chemistry
- Physical Chemistry
Background:
- Ion channels facilitate essential biological processes by controlling ion transport.
- The behavior of water molecules within these narrow channels is crucial for channel function.
- Understanding intrapore water structure and dynamics is key to elucidating channel mechanisms.
Purpose of the Study:
- To investigate the structure and dynamics of water confined within channel-like cavities.
- To compare intrapore water behavior with bulk water using molecular dynamics simulations.
- To analyze the influence of channel geometry on water molecule orientation and mobility.
Main Methods:
- Molecular dynamics simulations were employed using modified TIP3P water molecules.
- Cylindrical and hourglass-shaped cavities of varying radii and lengths were modeled.
- Analysis included water molecule orientation, self-diffusion coefficients, and rotational reorientation rates.
Main Results:
- Water molecules formed ordered concentric cylindrical shells within the cavities.
- Reduced water mobility was observed in narrower channels (3-6 Å radii) compared to bulk water.
- Water mobility approached bulk levels in wider channels (9-12 Å radii) and showed a gradient in hourglass cavities.
Conclusions:
- Confined water within simple channel models exhibits altered structure and dynamics relative to bulk water.
- Reduced rotational reorientation rates of intrapore water can modify the local dielectric constant.
- These findings provide insights into the biophysical properties of water within ion channels.