The size and structure of selected hydrated ions and implications for ion channel selectivity

Abstract

The part of the coordinated water around an ion in aqueous solution that is so strongly bound to the ion that it cannot be dissociated, known as hydration water, and the combination of the ion and hydration water, known as the hydrated ion, have been examined. An approach to determine the average volume and hydration number of hydrated ions has been developed and applied. Selected alkali metal and halogen hydrated ions were selected for analysis, according to their densities and the salt volume concentrations of aqueous solutions reported in the literature. The results of the new approach show that the effective radii and structures of hydrated Na⁺, K⁺, Rb⁺, and Cs⁺ play a key role in ion transport properties, such as ion channel selectivity.