Physiological Calcium Concentrations Slow Dynamics at the Lipid-Water Interface

Phospholipids can interact strongly with ions at physiological concentrations, and these interactions can alter membrane properties. Here, we describe the effects of calcium ions on the dynamics in phospholipid membranes. We used a combination of time-resolved ultrafast two-dimensional infrared spec...

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Bibliographic Details
Published in:Biophysical journal 2018-10, Vol.115 (8), p.1541-1551
Main Authors: Valentine, Mason L., Cardenas, Alfredo E., Elber, Ron, Baiz, Carlos R.
Format: Article
Language:English
Subjects:
Calcium - chemistry
Calcium - metabolism
Lipid Bilayers - chemistry
Lipid Bilayers - metabolism
Membranes
Molecular Dynamics Simulation
Phosphatidylcholines - chemistry
Phosphatidylcholines - metabolism
Phosphatidylserines - chemistry
Phosphatidylserines - metabolism
Water - chemistry
Water - metabolism
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Summary:Phospholipids can interact strongly with ions at physiological concentrations, and these interactions can alter membrane properties. Here, we describe the effects of calcium ions on the dynamics in phospholipid membranes. We used a combination of time-resolved ultrafast two-dimensional infrared spectroscopy and molecular dynamics simulations. We found that millimolar Ca2+ concentrations lead to slower fluctuations in the local environment at the lipid-water interface of membranes with phosphatidylserine. The effect was only observed in bilayers containing anionic phosphatidylserine; membranes composed of only zwitterionic phosphatidylcholine did not experience a slowdown. Local water dynamics were measured using the ester groups as label-free probes and were found to be up to 50% slower with 2.5 mM Ca2+. Molecular dynamics simulations show that Ca2+ primarily binds to the carboxylate group of phosphatidylserines. These findings have implications for apoptotic and diseased cells in which phosphatidylserine is exposed to extracellular calcium and for the biophysical effects of divalent cations on lipid bilayers.
ISSN:0006-3495
1542-0086
DOI:10.1016/j.bpj.2018.08.044