Hydration of sulfobetaine dizwitterions as a function of alkyl spacer length.

The solvation and structure of bolaform dizwitterions containing two sulfobetaine moieties in concentrated aqueous solution were determined using neutron diffraction with isotopic substitution (NDIS) combined with modelling of the measured structure factors using Empirical Potential Structure Refinement (EPSR). Strongly directional local hydration was observed in the polar regimes of the dizwitterions with 48-52 water molecules shared between dizwitterion molecules in a first shell water network around each zwitterion pair. Overall, the double zwitterions were highly hydrated, providing experimental evidence in support of the potential formation of protein-resistant hydration layers at zwitterion-water interfaces.

Multicharge zwitterionic molecules: Hydration, kosmotropicity and anti-fouling potential.

This manuscript presents a comparative study of the physico-chemical behaviour of sulfobetaine-type single and double zwitterions and zwitterionic salts, and structurally similar mono- and di-cationic tetraalkylammonium salts in aqueous solutions. The study includes experimental determination of the density and viscosity of highly diluted aqueous solutions with derivation of the Jones-Dole viscosity B-coefficient, partial molal volumes at infinite dilution, and hydration numbers. The study also examines the effects of addition of the salts on the surface tension of cationic and anionic surfactants, upper critical solution temperature of a non-ionic surfactant, solubility of amino acids, and stability of a protein. The experimental investigation was performed taking a broad bottom-up approach with the aim to elucidate the effect of molecular architecture and charge (two versus four) on the degree of surface hydration of a molecule, kosmotropicity, and interactions with charged and hydrophilic/hydrophobic surfaces - all-important characteristics which define ability of a functional group to resist protein attachment. The novel multicharged zwitterionic materials have exhibited superior qualities, thus paving the way to development of a new platform in design of hydrophilic and anti-fouling surfaces by employing the four-charge bearing molecular motifs.

Solubility-Modifying Power of Zwitterionic Salts.

The separation of small, hydrophilic molecules from aqueous solutions on one side and the dissolution of hydrophobic organic molecules in water on the other are nowadays among the most difficult challenges in chemical and bio-technology. Even though these two tasks are seemingly of opposite nature, it is demonstrated herein that both processes can be facilitated by addition of zwitterionic salts, a new class of compounds that can act either as a solubility enhancer or a phase-separation promoter depending on the structure of the solute dissolved in an aqueous solution. At a more fundamental level, this study investigates the salting in/out propensity of the ions and supports the importance of both salt-solute interaction and their concentration.