Molecular dynamics study of low molecular weight gel forming salt-triggered dipeptide.

Molecular dynamics simulation method was used to study the aggregation of Na and Ca salts in different concentrations of Naphthalene-dipeptide (2NapFF) solutions. The results show that high-valence Ca triggers the formation of a gel at a certain dipeptide concentration, and the low-valence Na system follows the aggregation law of general surfactants. The results also show that hydrophobic and electrostatic forces are the main driving forces for the formation of dipeptide aggregates, and that hydrogen bonds do not play a major role in the formation of dipeptide solution aggregates.

A novel colorimetric and fluorescent probe based on a core-extended perylene tetra-(alkoxycarbonyl) derivative for the selective sensing of fluoride ions.

A novel fluoride (F) colorimetric and fluorescent probe (P1) based on a core-extended perylene tetra-(alkoxycarbonyl) (PTAC) derivative was developed. The probe exhibited high sensitivity and selectivity for distinguishing F from other common anions through significant changes of the UV-Vis and fluorescence spectra. Job's plot analysis revealed that the stoichiometry of the P1-F interaction is 1 : 1.

Vesicles of a new salt-free cat-anionic fluoro/hydrocarbon surfactant system.

Weakly basic tetradecyldimethylaminoxide (C14DMAO) molecules can be protonated to form a cationic surfactant, C14DMAOH+, by an acidic fluorocarbon surfactant, an 8-2-fluorotelomer unsaturated acid (C7F15CF==CHCOOH), to form a salt-free cationic and anionic (cat-anionic) fluoro/hydrocarbon surfactant system in aqueous solution. The high Krafft point of C7F15CF==CHCOOH was largely reduced as a result of being mixed with a C14DMAO micelle solution. A study of the phase behavior of the new salt-free cat-anionic fluoro/hydrocarbon surfactant system clearly indicates the existence of a birefringent Lalpha-phase region at (25.

Ca2+- and ba2+-ligand coordinated unilamellar, multilamellar, and oligovesicular vesicles.

Ca(2+)- and Ba(2+)-coordinated vesicle phases were prepared in mixed aqueous solutions of tetradecyldimethylamine oxide (C(14)DMAO) and calcium oleate (Ca(OA)(2)) or barium oleate (Ba(OA)(2)). At the right mixing ratios, metal-ligand coordination between Ca(OA)(2) or Ba(OA)(2) and C(14)DMAO results in the formation of molecular bilayers due to the reduction in area per head group. Ca(2+) and Ba(2+) tightly associate to the head groups of surfactants and in this system the bilayer membranes are not shielded by excess salts.

Two routes to vesicle formation: metal-ligand complexation and ionic interactions.

Two routes to vesicle formation were designed to prepare uni- and multilamellar vesicles in salt-free aqueous solutions of surfactants. The formation of a surfactant complex between a double-chain anionic surfactant with a divalent-metal ion as the counterion and a single-chain zwitterionic surfactant with the polar group of amine-oxide group is described for the first time as a powerful driving force for vesicle-phases constructed from salt-free mixtures of aqueous surfactant solutions. As a typical example, a Zn(2+)-induced charged complex fluid, vesicle-phase has been studied in aqueous mixtures of tetradecyldimethylamine oxide (C(14)DMAO) and zinc 2,2-dihydroperfluorooctanoate [Zn(OOCCH(2)C(6)F(13))(2)].

A salt-free zero-charged aqueous onion-phase enhances the solubility of fullerene C60 in water.

An onion-phase (multilamellar vesicular phase or Lalpha-phase) was prepared from salt-free zero-charged cationic and anionic (catanionic) surfactant mixtures of tetradecyltrimethylammonium hydroxide (TTAOH)/lauric acid (LA)/H2O. The H+ and OH- counterions form water (TTAOH + LA --> TTAL + H2O), leaving the solution salt free. The onion-phase solution has novel properties including low conductivity, low osmotic pressure and unscreened electrostatic repulsions between cationic and anionic surfactants because of the absence of salt.