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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.

Electrospinning was employed to fabricate 3-D fiber networks from a recombinant amphiphilic elastin-mimetic tri-block protein polymer and the effects of moderate thermal conditioning (60°C, 4 h) on network mechanical responses investigated. Significantly, while cryo-high resolution scanning electron microscopy (cryo-HRSEM) revealed that the macroscopic and microscopic morphology of the network structure was unchanged, solid-state 1H-NMR spectroscopy demonstrated enhanced interphase mixing of hydrophobic and hydrophilic blocks. Significantly, thermal annealing triggered permanent changes in network swelling behavior (28.75 ± 2.80 non-annealed vs. 13.55 ± 1.39 annealed; P < 0.05) and uniaxial mechanical responses, including Young's modulus (0.170 ± 0.010 MPa non-annealed vs. 0.366 ± 0.05 MPa annealed; P < 0.05) and ultimate tensile strength (0.079 ± 0.008 MPa vs. 0.119 ± 0.015 MPa; P < 0.05). To our knowledge, these investigations are the first to note that mechanical responses of protein polymers can be permanently altered through a temperature-induced change in microphase mixing. [ABSTRACT FROM AUTHOR]

Self-assembling peptides have been previously designed that assemble into macroscopic membranes, nanotapes, and filaments through electrostatic interactions. However, the formation of highly ordered collagen-like fibrils, which display D-periodic features, has yet to be achieved. In this report, we describe for the first time a synthetic peptide system that self-assembles into a fibrous structure with well-defined periodicity that can be visualized by transmission electron microscopy (TEM). Specifically, we designed and synthesized a peptide that utilizes charged amino acids within the ubiquitous Xaa-Yaa-GIy triad sequence to bias the self-assembly into collagen-like homotrimeric helices that are capable of fibrillogenesis with the production of D-periodic microfibers. Potential molecular mechanisms for peptide assembly into triple-helical protomers and their subsequent organization into structurally defined, linear assemblies were explored through molecular dynamics (MD) simulations. The formation of thermodynamically stable complexes was attributed to the presence of strong electrostatic and hydrogen bond interactions at staggered positions along the linear assembly. This unexpected mimicry of native collagen structure using a relatively simple oligopeptide sequence establishes new opportunities for engineering linear assemblies with highly ordered nano- and microscale periodic features. In turn, the capacity to precisely design periodic elements into an assembly that faithfully reproduces these features over large length scales may facilitate the fabrication of ordered two- and three-dimensional fiber networks containing oriented biologically, chemically, or optically active elements. [ABSTRACT FROM AUTHOR]

A novel Dehalococcoides isolate capable of metabolic trichloroethene (TCE)-to-ethene reductive dechlorination was obtained from contaminated aquifer material. Growth studies and 16S rRNA gene-targeted analyses suggested culture purity; however, the careful quantitative analysis of Dehalococcoides 16S rRNA gene and chloroethene reductive dehalogenase gene (i.e., vcrA, tceA, and bvcA) copy numbers revealed that the culture consisted of multiple, distinct Dehalococcoides organisms. Subsequent transfers, along with quantitative PCR monitoring, yielded isolate GT, possessing only vcrA. These findings suggest that commonly used qualitative 16S rRNA gene-based procedures are insufficient to verify purity of Dehalococcoides cultures. Phylogenetic analysis revealed that strain GT is affiliated with the Pinellas group of the Dehalococcoides cluster and shares 100% 16S rRNA gene sequence identity with two other Dehalococcoides isolates, strain FL2 and strain CBDB1. The new isolate is distinct, as it respires the priority pollutants TCE, cis-1,2-dichloroethene (cis-DCE), 1,1-dichloroethene (1,1-DCE), and vinyl chloride (VC), thereby producing innocuous ethene and inorganic chloride. Strain GT dechlorinated TCE, cis-DCE, 1,1-DCE, and VC to ethene at rates up to 40, 41, 62, and 127 μmol liter-1 day-1, respectively, but failed to dechlorinate PCE. Hydrogen was the required electron donor, which was depleted to a consumption threshold concentration of 0.76 ± 0.13 nM with VC as the electron acceptor. In contrast to the known ICE dechlorinating isolates, strain GT dechlorinated TCE to ethene with very little formation of chlorinated intermediates, suggesting that this type of organism avoids the commonly observed accumulation of cis-DCE and VC during TCE-to-ethene dechlorination. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy (TEM) was used to investigate the crystal–collagen interactions in normal and osteoporotic human trabecular bone at the nanostructural level. More specifically, two-dimensional TEM observations were used to infer the three-dimensional information on the shape, the size, the orientation, and the alignment of apatite crystals in collagen fibrils in normal and osteoporotic bone. We found that crystals were of platelet shape with irregular edges and that there was no substantial difference in crystal length or crystal thickness between normal and osteoporotic trabecular bone. The crystal arrangement in cross-sectioned fibrils did not neatly conform to the parallel arrangement of crystals seen in longitudinally-sectioned fibrils. Instead, the crystal arrangement in both normal and osteoporotic trabecular bone took on more of a random, undulated arrangement, with certain localized areas demonstrating circular oriented patterns. The TEM imaging was done using bright fields only. Thus, the results presented are within the limitations of this approach. [Copyright &y& Elsevier]

Electrospinning was employed to fabricate 3-D fiber networks from a recombinant amphiphilic elastin-mimetic tri-block protein polymer and the effects of moderate thermal conditioning (60 degrees C, 4 h) on network mechanical responses investigated. Significantly, while cryo-high resolution scanning electron microscopy (cryo-HRSEM) revealed that the macroscopic and microscopic morphology of the network structure was unchanged, solid-state (1)H-NMR spectroscopy demonstrated enhanced interphase mixing of hydrophobic and hydrophilic blocks. Significantly, thermal annealing triggered permanent changes in network swelling behavior (28.75 +/- 2.80 non-annealed vs. 13.55 +/- 1.39 annealed; P < 0.05) and uniaxial mechanical responses, including Young's modulus (0.170 +/- 0.010 MPa non-annealed vs. 0.366 +/- 0.05 MPa annealed; P < 0.05) and ultimate tensile strength (0.079 +/- 0.008 MPa vs. 0.119 +/- 0.015 MPa; P < 0.05). To our knowledge, these investigations are the first to note that mechanical responses of protein polymers can be permanently altered through a temperature-induced change in microphase mixing., ((c) Koninklijke Brill NV, Leiden, 2009)

Simple oligopeptides that self-assemble into homogeneous nanotubes can be directed to further assemble into macroscale parallel arrays through protein "salting out" strategies.

Background: Although the use of polymer-based drug-eluting stents appears to markedly reduce the risk of in-stent restenosis, there are concerns about their safety including polymer layer integrity., Objectives: The objective of this study was to investigate the morphology of the polymer layer of 3 commercially available polymercoated stents, including the effects of balloon catheter expansion, by scanning electron microscopy (SEM)., Methods: We assessed discontinuities and other irregularities in the polymer layer of BiodivYsio, Taxus and Cypher stents by SEM after balloon expansion in saline solution at 37 degrees C., Results: Distinctive polymer layer morphologies were found among the 3 stent types, including responses to balloon expansion and withdrawal. The BiodivYsio stent showed no waving or other irregularities on the outer surface, but excess polymer was present on stent edges and polymer was peeled off from the inner surface. The Taxus stent showed no irregularities on the outer surface, but there were polymer bridgings across strut loops and linear cracking of the bridges, as well as inner surface polymer defects with bare-metal exposure. The Cypher stent showed a rough surface with irregularities and waving on the outer surface. There also appeared to be polymer defects with bare-metal exposure in the loop region and peeling of the top-coated polymer layer in the loop., Conclusions: We found several types of defects in the polymer layers on commercially available polymer-coated stents. Some of these indicate potential risks of thrombosis, coronary microembolism of polymer layer pieces and late inflammatory or neointimal reactions.

A bacterial isolate, designated strain SZ, was obtained from noncontaminated creek sediment microcosms based on its ability to derive energy from acetate oxidation coupled to tetrachloroethene (PCE)-to-cis-1,2-dichloroethene (cis-DCE) dechlorination (i.e., chlororespiration). Hydrogen and pyruvate served as alternate electron donors for strain SZ, and the range of electron acceptors included (reduced products are given in brackets) PCE and trichloroethene [cis-DCE], nitrate [ammonium], fumarate [succinate], Fe(III) [Fe(II)], malate [succinate], Mn(IV) [Mn(II)], U(VI) [U(IV)], and elemental sulfur [sulfide]. PCE and soluble Fe(III) (as ferric citrate) were reduced at rates of 56.5 and 164 nmol min(-1) mg of protein(-1), respectively, with acetate as the electron donor. Alternate electron acceptors, such as U(VI) and nitrate, did not inhibit PCE dechlorination and were consumed concomitantly. With PCE, Fe(III) (as ferric citrate), and nitrate as electron acceptors, H(2) was consumed to threshold concentrations of 0.08 +/- 0.03 nM, 0.16 +/- 0.07 nM, and 0.5 +/- 0.06 nM, respectively, and acetate was consumed to 3.0 +/- 2.1 nM, 1.2 +/- 0.5 nM, and 3.6 +/- 0.25 nM, respectively. Apparently, electron acceptor-specific acetate consumption threshold concentrations exist, suggesting that similar to the hydrogen threshold model, the measurement of acetate threshold concentrations offers an additional diagnostic tool to delineate terminal electron-accepting processes in anaerobic subsurface environments. Genetic and phenotypic analyses classify strain SZ as the type strain of the new species, Geobacter lovleyi sp. nov., with Geobacter (formerly Trichlorobacter) thiogenes as the closest relative. Furthermore, the analysis of 16S rRNA gene sequences recovered from PCE-dechlorinating consortia and chloroethene-contaminated subsurface environments suggests that Geobacter lovleyi belongs to a distinct, dechlorinating clade within the metal-reducing Geobacter group. 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.

Surfactants 3 (tripotassium O,O'-di-[11-(carboxylato)undecyl]phosphorodithioate) and 4 (sodium 12-[dimethyl-(11-carboxylatoundecyl)ammonio]dodecanoate), which are new shamrock surfactants, were prepared and characterized. Shamrock surfactants represent a novel class of surfactants that contain a central headgroup connected to two flanking headgroups by hydrocarbon chains; they do not contain long-chain alkyl groups. Surfactants 3 and 4 were characterized in water by measurement of their Krafft temperatures and critical aggregation concentrations, and their aggregates were studied by 1H and 31P NMR spectroscopy, dynamic laser light scattering, and phase-contrast optical microscopy. Aqueous 3 and 4 were also studied by cryoetch high-resolution scanning electron microscopy, which revealed fences with interposed lacelike patterns for the former and compartments formed by irregular fences for the latter. Coacervates were likely formed upon the undisturbed hydration of 3 and 4, as determined by phase-contrast optical microscopy.

Quaternary ammonium surfactants with the hydrotris(1-pyrazolyl)borate anion as an unusual counterion were prepared and characterized. Dodecyl- (1a), tetradecyl- (1b), and hexadecyltrimethylammonium hydrotris(1-pyrazolyl)borate (1c), as well as didodecyldimethylammonium hydrotris(1-pyrazolyl)borate (2), were prepared by metathesis reactions with the corresponding quaternary ammonium bromides and potassium hydrotris(1-pyrazolyl)borate (4). Although the surfactants have limited stabilities in water at 23 degrees C, they were characterized by measurement of their Krafft temperatures and critical aggregation concentrations. (1)H NMR spectroscopy suggested that the single-chain surfactants 1 form small aggregates in water and revealed an association of the quaternary ammonium and hydrotris(1-pyrazolyl)borate ions above their critical aggregation concentrations. Cryo-etch high-resolution scanning electron microscopy indicated that 1a and 1b most likely form segregation patterns upon plunge-freezing and cryo-etching of their aqueous solutions, and a single-crystal X-ray diffraction study of 1a was performed.

Two types of a new class of surfactants with three headgroups, which possess the general structure 1, have been prepared. Within structure 1, a central headgroup is connected to two flanking headgroups by hydrocarbon chains. The term "shamrock" is used to describe surfactants of structure 1, denoting their triple-headed character and reflecting the fact that shamrocks have leaflets in groups of three. The major lipophilic character of shamrock surfactants is provided by the two hydrocarbon chains linking the three headgroups and not by long-chain alkyl groups appended to the linking hydrocarbon chains or the headgroups. The new surfactants are 2a (2,2,15,15,28,28-hexamethyl-2,15,28-triazonianonacosane triiodide), 2b (2,2,15,15,28,28-hexamethyl-2,15,28-triazonianonacosane trichloride), 3a (O,O'-di-[10-(N,N,N-tripropylammonio)decyl]phosphorodithioate bromide), and 3b (O,O'-di-[10-(N,N,N-tributylammonio)decyl]phosphorodithioate bromide). Compound 14 (2,2,9,9,16,16-hexamethyl-2,9,16-triazoniaheptadecane triiodide) was prepared for comparison with 2a. Surfactants 2 and 3 were characterized in water by measurement of their Krafft temperatures and critical aggregation concentrations, and their aggregates were studied by 1H NMR spectroscopy, dynamic laser light scattering, and phase-contrast optical microscopy. Aqueous 2b was also studied by cryo-etch high-resolution scanning electron microscopy, which revealed irregularly shaped cells containing a complex matrix of surfactant. Coacervates were observed by optical microscopy upon the hydration of 2 and 3.

Glycopolymer-polypeptide triblock copolymers of the structure, poly(l-alanine)-b-poly(2-acryloyloxyethyl-lactoside)-b-poly(l-alanine) (AGA), have been synthesized by sequential atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP). Controlled free radical polymerization of 2-O-acryloyl-oxyethoxyl-(2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)-(1-4)-2,3,6-tri-O-acetyl-beta-d-glucopyranoside (AEL) by ATRP with a dibromoxylene (DBX)/CuBr/bipy complex system was used to generate a central glycopolymer block. Telechelic glycopolymers with diamino end groups were obtained by end group transformation and subsequently used as macroinitiators for ROP of l-alanine N-carboxyanhydride monomers (Ala-NCA). Gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy analysis demonstrated that copolymer molecular weight and composition were controlled by both the molar ratios of the Ala-NCA monomer to macroinitiator and monomer conversion and exhibited a narrow distribution (Mw/Mn = 1.06-1.26). FT-IR spectroscopy of triblock copolymers revealed that the ratio of alpha-helix/beta-sheet increased with poly(l-alanine) block length. Of note, transmission electron microscopy (TEM) demonstrated that selected amphiphilic glycopolymer-polypeptide triblock copolymers self-assemble in aqueous solution to form nearly spherical aggregates of several hundreds nanometer in diameter. Significantly, the sequential application of ATRP and ROP techniques provides an effective method for producing triblock copolymers with a central glycopolymer block and flanking polypeptide blocks of defined architecture, controlled molecular weight, and low polydispersity.

The micro- and nanoarchitectures of water-swollen hydrogels were routinely analyzed in three dimensions at very high resolution by two cryopreparation methods that provide stable low-temperature specimens for in-lens high magnification recordings. Gemini surfactants (gS), poly-N-isopropylacrylamides (p-NIP Am), and elastin-mimetic di- (db-E) and triblock (tb-E) copolymer proteins that form hydrogels have been routinely analyzed to the sub-10-nm level in a single day. After they were quench or high pressure frozen, samples in bulk planchets were subsequently chromium coated and observed at low temperature in an in-lens field emission SEM. Pre-equilibrated planchets (4-40 degrees C) that hold 5-10 microl of hydrogel facilitate dynamic morphological studies above and below their transition temperatures. Rapidly frozen samples were fractured under liquid nitrogen, low-temperature metal coated, and observed in-lens to assess the dispersion characteristics of micelles and fragile colloidal assemblies within bulk frozen water. Utilizing the same planchet freezing system, the cryoetch-HRSEM technique removed bulk frozen water from the hydrogel matrix by low-temperature, high-vacuum sublimation. The remaining frozen solid-state sample faithfully represented the hydrogel matrix. Cryo- and cryoetch-HRSEM provided vast vistas of hydrogels at low and intermediate magnifications whereas high magnification recordings and anaglyphs (stereo images) provided a three-dimensional prospective and measurements on a molecular level.

Elastin-mimetic block copolymers were produced by genetic engineering. Genetically driven synthesis permitted control of the final physiochemical characteristics of the block copolymers. We designed BB and BAB block copolymers in which the A-block was hydrophilic and the B-block was hydrophobic. By designing the copolymers in this manner, it was proposed that they would self-assemble into micellar aggregates that, at high concentration, would form thermoreversible hydrogels. To analyze the three-dimensional fine surface morphology of the copolymers, to the resolution level of a few nanometers, we employed cryo-HRSEM. This method provided vast expanses of the specimen in its frozen hydrated state for survey. In our initial cryo-HRSEM studies, we observed the protein filaments and micelles surrounded by lakes of vitreous ice. Upon examination at low and intermediate magnifications, there was an extensive honeycomb-like filamentous network. To delineate the fine morphology of the hydrogel network at high magnification and to greater depths, we cryoetched away unbound water from the sample surface, in high vacuum, prior to chromium deposition. By using this technique, we were able to visualize for characterization purposes the fine fibril networks formed from the micellar aggregates over the surface of the hydrogel.