Opposing Roles of Cholesterol and Cholesterol Sulfate in Proton Transfer and Diffusion at Membrane Interfaces

Cholesterol sulfate (ChS) inhibits local excited-state proton transfer in gel-phase phosphatidylcholine bilayers, while increasing long-range lateral proton conductance by 400-fold in supported bilayers under controlled humidity.

• Why it matters: Sterols shape membrane structure, but how they differentially control interfacial proton transfer versus long-range proton diffusion is not well defined.
• What they did: The study used a membrane-anchored photoacid in small unilamellar vesicles plus molecular dynamics simulations to track local excited-state proton transfer, and solid-state electrical measurements on supported lipid bilayers to quantify lateral proton conduction.
• The result: Ch accelerates local proton transfer by inducing a fluid liquid-ordered phase, whereas ChS inhibits it via deeper embedding and lower sulfate basicity; for lateral proton diffusion, ChS boosts conductance 400-fold by providing titratable sulfate carriers, while Ch reduces it by diluting phosphate mediators.

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