How strongly can calcium ion influence the hydrogen-bond dynamics at complex aqueous interfaces?

The author has performed three independent molecular dynamics computer simulations to examine the effects of counterion identity on hydrogen-bond dynamics in the enclosed water pool of anionic surfactant-based reverse micelles. The water-water hydrogen-bond lifetime in the reverse micelle (RM) with calcium ions is found to be longer than that in the RM with sodium or ammonium ions. The hydrogen bond between a polar head group and a water molecule, on the other hand, breaks but reforms most rapidly in the RM with calcium ions, indicating that there exists a strong competition between head group-counterion and head group-water interactions at such complex interfaces. © 2007 American Institute of Physics.