Interestingly (well to me) this is also how some ion channels in cells work - the solvation shell (water cage) allows protein pores to distinguish between sodium and potassium.
Not sure this is the best paper, just a random pick :
https://www.sciencedirect.com/science/article/abs/pii/S09692...
Huh. More complex than I understood:
"...there are two groups of hypotheses explaining the selectivity on the basis of molecular dynamics (MD) simulations. The first group mainly considers flexibility/mobility of the carboxyl groups in the EEEE ring that provides a preferable space-charge environment for partly hydrated Na+ ions to pass and an unfavorable environment for K+.19,20,21 The second group proposes the “steric” selectivity mechanism, suggesting that the SF of Navs is not wide enough to let a fully hydrated K+ pass through, while fully hydrated Na+ traverses through the pore without a significant barrier"
Different paper about the 'selectivity filter' https://www.frontiersin.org/journals/physiology/articles/10....
"The backbone carbonyl oxygens plus the hydroxyl group of the threonine form four ion binding sites, called S1 to S4 from the extracellular side (see Figure 1A), and they perfectly mimic the hydration shell of potassium ions"
What I like about the selectivity filter is that it uses the backbone carbonyls.
Not sure this is the best paper, just a random pick :
https://www.sciencedirect.com/science/article/abs/pii/S09692...
Huh. More complex than I understood:
"...there are two groups of hypotheses explaining the selectivity on the basis of molecular dynamics (MD) simulations. The first group mainly considers flexibility/mobility of the carboxyl groups in the EEEE ring that provides a preferable space-charge environment for partly hydrated Na+ ions to pass and an unfavorable environment for K+.19,20,21 The second group proposes the “steric” selectivity mechanism, suggesting that the SF of Navs is not wide enough to let a fully hydrated K+ pass through, while fully hydrated Na+ traverses through the pore without a significant barrier"
Different paper about the 'selectivity filter' https://www.frontiersin.org/journals/physiology/articles/10....
"The backbone carbonyl oxygens plus the hydroxyl group of the threonine form four ion binding sites, called S1 to S4 from the extracellular side (see Figure 1A), and they perfectly mimic the hydration shell of potassium ions"
What I like about the selectivity filter is that it uses the backbone carbonyls.
https://gilleain-torrance.net