Identification of dissolved organic matter size components in freshwater and marine environments

Dissolved organic matter (DOM) in the transition zone from freshwater to marine systems was analyzed with a new approach for parameterizing the size distribution of organic compounds. We used size-exclusion chromatography for molecular size analysis and quantified colored DOM (CDOM) on samples from two coastal environments in the Baltic Sea (Roskilde Fjord, Denmark and Gulf of Gdansk, Poland). We applied a Gaussian decomposition method to identify peaks from the chromatograms, providing information beyond bulk size properties. This approach complements methods where DOM is separated into size classes with pre-defined filtering cutoffs, or methods where chromatograms are used only to infer average molecular weight. With this decomposition method, we extracted between three and five peaks from each chromatogram and clustered these into three size groups. To test the applicability of our method, we linked our decomposed peaks with salinity, a major environmental driver in the freshwater-marine continuum. Our results show that when moving from freshwater to low-salinity coastal waters, the observed steep decrease of apparent molecular weight is mostly due to loss of the high-molecular-weight fraction (HMW; >2 kDa) of CDOM. Furthermore, most of the CDOM absorbance in freshwater originates from HMW DOM, whereas the absorbing moieties are more equally distributed along the smaller size range (<2 kDa) in marine samples.Peer reviewe

Electrospun Polyurethane Fibers for Absorption of Volatile Organic Compounds from Air

Electrospun polyurethane fibers for removal of volatile organic compounds (VOC) from air with rapid VOC absorption and desorption have been developed. Polyurethanes based on 4,4-methylenebis(phenylisocyanate) (MDI) and aliphatic isophorone diisocyanate as the hard segments and butanediol and tetramethylene glycol as the soft segments were electrospun from their solutions in N,N-dimethylformamide to form micrometer-sized fibers. Although activated carbon possessed a many-fold higher surface area than the polyurethane fiber meshes, the sorption capacity of the polyurethane fibers was found to be similar to that of activated carbon specifically designed for vapor adsorption. Furthermore, in contrast to VOC sorption on activated carbon, where complete regeneration of the adsorbent was not possible, the polyurethane fibers demonstrated a completely reversible absorption and desorption, with desorption obtained by a simple purging with nitrogen at room temperature. The fibers possessed a high affinity toward toluene and chloroform, but aliphatic hexane lacked the necessary strong attractive interactions with the polyurethane chains and therefore was less strongly absorbed. The selectivity of the polyurethane fibers toward different vapors, along with the ease of regeneration, makes them attractive materials for VOC filtration.Boeing CompanyNetherlands Organisation for Scientific Research (NWO) (Talent Scholarship

Purification and Characterization of Fimbriae from Fimbriate Vibrio cholerae O1 Strain Bgd17

Fimbrillin (or pilin) of Vibrio cholerae O1, purified both from an E1 Tor strain and a classical strain was shown to have the indentical N-terminal amino acid sequence which is extensively homologous to those of the N-methylphenyl alanine (NMePhe) pilin molecules and partly homologous to that of TcpA (Taylor et al., 1987; Show and Taylor, 1990). The N-terminal amino acid residue of the fimbrillin was modified and has not been determined. Haemagglutinin (HA) activities of the purified fimbriae were completely inhibited by D-mannnose and D-glucose, but not by L-fucose. Interestingly, pellicle formation of fimbriate cells was also inhibited by D-mannnose and D-glucose but not by L-fucose as shown previously. Based on the hypothesis that fimbriae of V. cholerae O1 function as the colonization factor and the cell associated haemagglutinin, this correlation in inhibition by monosaccharides between HA activity and pellicle formation strongly suggests that D-glucose in Oral Rehydration Salts (ORS, recommended for treatment by World Health Organization) can reduce the clinical symptom (diarrhoea) by inhibiting the colonization of vibrio cells to the epithelial cells of the upper small intestine. The presence of fimbrial antigens among enteropathogenic V. cholerae O1 strains was confirmed by western blot- and dot blot-analyses. The fimbrillin of the strain Bgd17 was shown to be a simple protein. Immunoelectron microscopy of the fimbriae with a specific monoclonal antibody revealed that fimbriae of V. cholerae O1 function as fimbrial adhesins necessary for the cell-cell interaction

Selective Induction of Fimbriate Vibrio cholerae O1

Fimbriate Vibrio cholerae O1 (classical in biotype) were selectively induced in the presence of chitin and thioproline. Fimbriate vibrios detectable by cell agglutination with anti-E1 Tor fimbriae antiserum formed pellicle when cultured in liquid media under static conditions and were highly hydrophobic. Fimbriate vibrios agglutinated several kinds of red blood cells (RBCs, human type O, sheep, chicken, horse) and showed highest haemag-glutinating (HA) activity for horse-RBCs, although parent non-fimbriate cells had no HA activity. Pellicle formation and HA activity of fimbriate cells were completely inhibited by 1% monosaccharides such as D-mannose, D-glucose, D-fructose, N-acetyl-D-glucosamine, but not by L-fucose. Numerous pores with a regular diameter were found on an outer membrane debris through which fimbriae may extend extracellularly