Competing for the same space: protons and alkali ions at the interface of phospholipid bilayers
Maintaining gradients of solvated protons and alkali metal ions such as Na+ and K+ across membranes is critical for cellular function. Over the last few decades, both the interactions of protons and alkali metal ions with phospholipid membranes have been studied extensively and the reported interactions of these ions with phospholipid headgroups are very similar, yet few studies have investigated the potential interdependence between proton and alkali metal ion binding at the water–lipid interface. In this short review, we discuss the similarities between the proton–membrane and alkali ion–membrane interactions. Such interactions include cation attraction to the phosphate and carbonyl oxygens of the phospholipid headgroups that form strong lipid–ion and lipid–ion–water complexes. We also propose potential mechanisms that may modulate the affinities of these cationic species to the water–phospholipid interfacial oxygen moieties. This review aims to highlight the potential interdependence between protons and alkali metal ions at the membrane surface and encourage a more nuanced understanding of the complex nature of these biologically relevant processes.
KeywordsProtons Hydronium ions Alkali ions Ion lipid interactions Membranes Lipid bilayers
The authors wish to acknowledge Adj Prof Bruce Cornell (UTS), Associate Prof Ron Clarke (University of Sydney), Dr Stephen Holt (Australian Nuclear Science and Technology Organisation) and Dr Paul Duckworth (eDAQ Pty Ltd) for valuable discussions on these topics.
Compliance with ethical standards
ED and AG are supported by the UTS Chancellor’s Postdoctoral Research Fellowship scheme.
Conflicts of interest
Evelyne Deplazes declares that she has no conflict of interest. Jacqueline White declares that she has no conflict of interest. Christopher Murphy declares that he has no conflict of interest. Charles G Cranfield declares that he has no conflict of interest. Alvaro Garcia declares that he has no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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