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Near-membrane electric field calcium ion dehydration
James P Barger1, Patrick F Dillon1
1Department of Physiology, Michigan State University, 567 Wilson Rd., East Lansing, MI 48824, USA.
Cell Calcium
|September 30, 2016
Summary
Membrane electric fields can dehydrate calcium ions before they enter ion channels. This electric field-induced water stripping occurs near the cell membrane, impacting ion transport.
Area of Science:
- Biophysics
- Electrochemistry
- Membrane Biology
Background:
- Ion channel function is crucial for cellular processes.
- Hydration state of ions influences their passage through membrane channels.
- Previous research focused on protein-mediated water dissociation, neglecting electric field effects.
Purpose of the Study:
- To investigate the role of membrane electric fields in dehydrating ions.
- To quantify the electric fields required to remove water from calcium ions.
- To understand the implications of ion dehydration for ion channel transit.
Main Methods:
- Capillary electrophoresis was used to measure ion migration velocity under varying electric fields.
- Stokes' equation was adapted to calculate hydrated ion radii.
- A tanh function modeled the transition from hydrated to dehydrated states.
Main Results:
- Calcium ion hydration shells were experimentally determined (0.334nm radius, ~5 water molecules).
- Increasing electric fields progressively stripped water molecules from calcium ions.
- Dehydration occurred 6-7nm from the membrane, preceding channel entry.
Conclusions:
- Membrane electric fields can actively dehydrate ions like calcium before channel transit.
- This electric field-induced dehydration is a significant factor in ion transport across membranes.
- Ions reaching channel pores are likely to be stripped of their water shells, irrespective of pore structure.
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