Search

In this work, three amino acid-derived (L-leucinol, L-isoleucinol, L-valinol) sulfated chiral surfactants are synthesized and polymerized. These chiral sulfated surfactants are thoroughly characterized to determine critical micelle concentration, aggregation number, polarity, optical rotation, and partial specific volume. For the first time the morphological behavior of polymeric sulfated surfactants is revealed using cryogenic high-resolution electron microscopy. The polysodium N-undecenoyl-L-leucine sulfate shows distinct tubular structure, while polysodium N-undecenoyl-L-valine sulfate also shows tubular morphology but without any distinct order of the tubes. On the other hand, polysodium N-undecenoyl-L-isoleucine sulfate (poly-L-SUCILS) displays random distribution of coiled/curved filaments with heavy association of tightly and loosely bound water. All three polymeric sulfated surfactants are compared for enantioseparation of a broad range of structurally diverse racemic compounds at very acidic, neutral, and basic pH conditions in micellar electrokinetic chromatography (MEKC). A small combinatorial library of 10 structurally related phenylethylamines (PEAs) is investigated for chiral separation under acidic and moderately acidic to neutral pH conditions using an experimental design. In contrast to neutral pH conditions, at acidic pH, significantly enhanced chiral resolution is obtained for class I and class II PEAs due to the compact structure of polymeric sulfated surfactants. It is observed that the presence of a hydroxy group on the benzene ring of PEAs resulted in deterioration of enantioseparation. A sensitive MEKC-mass spectrometry (MS) method is developed for one of the PEAs (e.g., ([+ or-])-pseudoephedrine) in human urine. Very low limit of detection (LOD) is obtained at pH 2.0 (LOD 325 ng/mL), which is ~16 times better compared to pH 8.0 (LOD 5.2 [micro]g/mL). Another broad range of chiral analytes ([beta]-blockers, phenoxypropionic acid, benzoin derivatives, PTH-amino acids, benzodiazepinones) studied also provided improved chiral separation at low pH compared to high-pH conditions. Among the three polymeric sulfated surfactants, poly-L-SUCILS with two chiral centers on the polymer head group provided overall higher enantio-resolution for the investigated acidic, basic, and neutral compounds. This work clearly demonstrates for the first time the superiority of chiral separation and sensitive MS detection at low pH over conventional high-pH chiral separation and detection employing anionic chiral polymeric surfactants in MEKC and MEKC-MS.

A novel Dehalococcoides isolate that uses trichloroethene (TCE), cis-DCE, 1, 1-dichloroethene (1, 1-DCE), and vinyl chloride as metabolic acceptors and forms negligible amounts of toxic intermediates during TCE dechlorination. Phylogenetic analysis revealed that strain GT is affiliated with the Pinellas group of the Dehalococcoides cluster and shares 100 percent 16S rRNA gene sequence identity with two other dehalococcoides isolates, strain FL2 and strain CBCD1.

The synthesis of a new class of asymmetric phospholipid bolaamphhiphiles and the initial investigations of the self-assembly of these compounds in both organic and aqueous media are discussed. Asymmetric lipid bolaamphiphiles would provide facile building blocks for engineering a variety of unique membrane-mimetic structures.

The article presents a new approach for the synthesis and self-assembly of the D-periodic collagen-mimetic microfibers. The formed complexes are found to be highly stable due to the presence of strong electrostatic and hydrogen bond interactions.

A bacterial isolate, designated strain SZ, is obtained from noncontaminated creek sediment microcosms based on its ability to derive energy from acetate oxidation coupled to tetrachloroethane (PCE)-to-cis-1,2-dichloroethene (cis-DCE) dechlorination. Substrate versatility, consumption of electron donors to low threshold concentrations, and simultaneous reduction of electron acceptors suggest that strain SZ-type organisms have desirable characteristics for bioremediation applications.

A study on ice formation from saline at concentrations near that of seawater, by cryo-etch high-resolution scanning electron microscopy, is presented. The study reveals some surprising morphologies.

A remarkable parallel between jointing in geological formations and jointing in vitreous ice containing a surfactant when observed by cryo- high resolution scanning electron microscopy (cryo- HRSEM) is described. The method can be particularly useful and non invasive for discovering new modes of self assembly in water.

The design and characterization of a peptide, TZ1H, is presented that is based on a trimeric coiled-coil motif that reversibly assembles into long-aspect-ratio helical fibrils as a consequence of a pH-induced conformational transition. The results have shown that the self-assembly of a de novo-designed peptide into a supramolecular material can be controlled reversibly through a mechanism that couples histidine side-chain proton-transfer equilibria to peptide conformation.

The study data imply the importance of inter-sheet contacts in amyloid nucleation. The results are consistent with Bush's finding that the mouse A-beta sequence, which contains an H13R mutation, is more tolerant of metal exposure than the human sequence, and relate to the continuing discussion of methods to control amyloid deposition in this context.

The information-content of cryo-etch-HRSEM pictorial but distinctive in nature, is illustrated with gel and coacervate systems formed from a new series of Gemini surfactants. Cryo-etch-HRSEM pictures reveal a rough surface consistent with a colony of spherical vesicles projecting from the ice.