Sodium and potassium ions form a two-dimensional structure below a lipid monolayer floating on water

What is it about?

Sodium and potassium ions and their ratios play the crucial role in sending electrical signals across cell membranes. We wanted to see how they may bind to the membrane and affect its structure and mechanical properties. We looked at sodium and potassium ions and their mixtures dissolved in water on which a monolayer of a phospholipid is floating, this phospholipid being a major component of cell membranes. We found that the variation in bonding, structure and rigidity of the monolayer due to the presence of these ions can be explained only if the ions are distributed in a two-dimensional structure beneath the lipid monolayer.

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Why is it important?

Sodium and potassium ions were thought to be present as diffuse dispersions at the external and internal surfaces of the cell membranes. This work shows that they are much more structured and this changes the whole physics about their electrical interaction with the membrane in particular and the dynamics of the signal transport across the membrane.