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Type I collagen-PEO fibers and non-woven fiber networks were produced by the electrospinning of a weak acid solution of purified collagen at ambient temperature and pressure. As determined by high-resolution SEM and TEM. fiber morphology was influenced by solution viscosity, conductivity, and flow rate. Uniform fibers with a diameter range of 100-150 nm were produced from a 2-wt% solution of collagen-PEO at a flow rate of 100 microl min(-1). Ultimate tensile strength and elastic modulus of the resulting non-woven fabrics was dependent upon the chosen weight ratio of the collagen-PEO blend. 1H NMR dipolar magnetization transfer analysis suggested that the superior mechanical properties, observed for collagen-PEO blends of weight ratio 1:1, were due to the maximization of intermolecular interactions between the PEO and collagen components. The process outlined herein provides a convenient, non-toxic, non-denaturing approach for the generation collagen-containing nanofibers and non-woven fabrics that have potential application in wound healing, tissue engineering, and as hemostatic agents.

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 mol 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 TCE 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.Chlorinated ethenes are pervasive groundwater contaminants resulting from extensive usage, improper disposal, and accidental spills, and the incomplete microbial dechlorination of tetrachloroethene (PCE) and trichloroethene (TCE) leads to dichloroethene and vinyl chloride (VG) accumulation. A breakthrough in the anaerobic treatment of chloroethene-contaminated sites was the discovery of bacteria that use chloroorganic compounds as electron acceptors to drive their energy metabolism. This metabolic reductive dechlorination process, also known as (de)chlororespiration, is a focus of current bioremediation approaches to contain or remediate chloroethene plumes.Numerous bacterial isolates that reductively dechlorinate chloroethenes have been described previously (26); however, no single organism has the ability to couple energy generation with each reductive dechlorination step leading from PCE to ethene. The majority of isolates dechlorinate PCE to cis-1,2-dichloroethene (cis-DCE), and the ability to respire PCE to cis-DCE is distributed among phylogenetic groups and includes members of the classes Deltaproteobacteria, Gammaproteobacteria, and Firmicutes (14). Bacteria with the ability for incomplete dechlorination of PCE to cis-DCE are often present at co...

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 , 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 electronaccepting 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.Environmental pollutants, such as chlorinated solvents, toxic metals, and radionuclides (e.g., uranium), are strictly regulated due to their negative effects on ecosystem function and human health. Tetrachloroethene (PCE) and trichloroethene (TCE) are frequently used as solvents and degreasing agents. As a result of extensive usage, improper disposal, and accidental spills, PCE and TCE became widely distributed, pervasive groundwater contaminants. Uranium was released in significant amounts from nuclear weapon complexes managed by the U.S. Department of Energy (DOE) during the Cold War arms race. It was estimated that more than 80% of DOE sites have radionuclide contamination and at least 27% have volatile organic hydrocarbons as cocontaminants (47).The considerable knowledge that has accrued on the fate of specific contaminants and the bacteria involved in the transformation and degradation pathways has led to successful bioremediation field studies. For instance, acetate additions to stimulate dissimilatory metal-reducing organisms promoted reduction of soluble U(VI) to insoluble U(IV) and contributed to plume containment (2,...

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-Gly 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.