Dehydration Determines Hydrotropic Ion Affinity for Zwitterionic Micelles

Abstract

Specific ion effects in zwitterionic micelles, especially for anions, are evident in reaction kinetics, zeta potential, and critical micelle concentration measurements. However, anion adsorption to zwitterionic micelles does not produce significant changes in shape, aggregation number, or interfacial hydration. Here we used molecular dynamics simulation of systems containing sulfobetaine zwitterionic micelles of N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DPS) and nine different salts to explore ion adsorption in terms of group dehydration. Our results, in line with those obtained for cationic micelles, showed that the adsorption degree of anions containing both hydrophobic and hydrophilic portions, i.e., hydrotropes, were correlated with the ion dehydration and were governed mainly by the hydrophobic portion dehydration upon adsorption.

Short-chain branched sulfosuccinate as a missing link between surfactants and hydrotropes

“…Classical surfactants show similar behavior, with the drastically reduced hydration of the hydrophobic chain atoms, while the head group hydration is mostly unaffected. 42 The even higher decrease in the hydration of the linker is explained by the change in the geometry of the molecule during aggregation. During aggregation, the hydrophobic tails cluster, which influences the torsion angle of the succinate group and the hydration of the linker is sterically hindered.…”

“…Classical surfactants show similar behavior, with the drastically reduced hydration of the hydrophobic chain atoms, while the head group hydration is mostly unaffected. 42 The even higher decrease in the hydration of the linker is explained by the change in the geometry of the molecule during aggregation.…”

Model Membrane Interactions and Biological Activity of a Naphthalimide-Containing BP100

“…Enthalpy variation can be ascribed to electrostatic interactions between NAPHT-BP100 and the membrane surface, while entropy variations are most likely related to peptide dehydration and hydrophobic interactions between peptide hydrophobic helix face and lipid acyl chains. Binding of some hydrotropic ions to zwitterionic interfaces is controlled by the dehydration of their hydrophobic moieties [45].…”

Osmotic Method for Calculating Surface Pressure of Monolayers in Molecular Dynamics Simulations

“…For insoluble monolayers, ,, where ω and a w are the partial molar surface area and the interfacial activity of water, respectively. Since a couple of surface pressure-dependent phenomena are correlated to the interfacial activity of water, they can be promptly investigated using the methodology proposed in this Letter. − …”