123 research outputs found
Stress response of Pseudomonas aeruginosa to sodium hypochlorite leads to enhanced biofilm formation
Decision tree supported substructure prediction of metabolites from GC-MS profiles
Gas chromatography coupled to mass spectrometry (GC-MS) is one of the most widespread routine technologies applied to the large scale screening and discovery of novel metabolic biomarkers. However, currently the majority of mass spectral tags (MSTs) remains unidentified due to the lack of authenticated pure reference substances required for compound identification by GC-MS. Here, we accessed the information on reference compounds stored in the Golm Metabolome Database (GMD) to apply supervised machine learning approaches to the classification and identification of unidentified MSTs without relying on library searches. Non-annotated MSTs with mass spectral and retention index (RI) information together with data of already identified metabolites and reference substances have been archived in the GMD. Structural feature extraction was applied to sub-divide the metabolite space contained in the GMD and to define the prediction target classes. Decision tree (DT)-based prediction of the most frequent substructures based on mass spectral features and RI information is demonstrated to result in highly sensitive and specific detections of sub-structures contained in the compounds. The underlying set of DTs can be inspected by the user and are made available for batch processing via SOAP (Simple Object Access Protocol)-based web services. The GMD mass spectral library with the integrated DTs is freely accessible for non-commercial use at http://gmd.mpimp-golm.mpg.de/. All matching and structure search functionalities are available as SOAP-based web services. A XMLÂ +Â HTTP interface, which follows Representational State Transfer (REST) principles, facilitates read-only access to data base entities
Hydrophobically Modified Sulfobetaine Copolymers with Tunable Aqueous UCST through Postpolymerization Modification of Poly(pentafluorophenyl acrylate)
Polysulfobetaines, polymers carrying highly polar zwitterionic side chains, present a promising research field by virtue of their antifouling properties, hemocompatibility, and stimulus-responsive behavior. However, limited synthetic approaches exist to produce sulfobetaine copolymers comprising hydrophobic components. Postpolymerization modification of an activated ester precursor, poly(pentafluorophenyl acrylate), employing a zwitterionic amine, 3-((3-aminopropyl)dimethylammonio)propane-1-sulfonate, ADPS, is presented as a novel, one-step synthetic concept toward sulfobetaine (co)polymers. Modifications were performed in homogeneous solution using propylene carbonate as solvent with mixtures of ADPS and pentylamine, benzylamine, and dodecylamine producing a series of well-defined statistical acrylamido sulfobetaine copolymers containing hydrophobic pentyl, benzyl, or dodecylacrylamide comonomers with well-controllable molar composition as evidenced by NMR and FT-IR spectroscopy and size exclusion chromatography.This synthetic strategy was exploited to investigate, for the first time, the influence of hydrophobic modification on the upper critical solution temperature (UCST) of sulfobetaine copolymers in aqueous solution. Surprisingly, incorporation of pentyl groups was found to increase solubility over a wide composition range, whereas benzyl groups decreased solubilityâan effect attributed to different entropic and enthalpic contributions of both functional groups. While UCST transitions of polysulfobetaines are typically limited to higher molar mass samples, incorporation of 0â65 mol % of benzyl groups into copolymers with molar masses of 25.5â34.5 kg/mol enabled sharp, reversible transitions from 6 to 82 °C in solutions containing up to 76 mM NaCl, as observed by optical transmittance and dynamic light scattering. Both synthesis and systematic UCST increase of sulfobetaine copolymers presented here are expected to expand the scope and applicability of these smart materials
FullereneâOligophenylenevinylene Hybrids: Synthesis, Electronic Properties, and Incorporation in Photovoltaic Devices
Full Discretisations for Nonlinear Evolutionary Inequalities Based on Stiffly Accurate RungeâKutta and hp-Finite Element Methods
Wheat roots efflux a diverse array of organic N compounds and are highly proficient at their recapture
Investigation of lignin obtained by processing of Betula pendula with ionic liquids
Imidazolium-based ionic liquids bearing chloride, acetate, mesylate, and tosylate as anion were investigated for the treatment of birch (Betula pendula) bark to extract lignin. Although birch bark was previously extracted with methanol to remove low molecular weight organic compounds, various fatty acids and ferulic acid esters were analyzed in the lignin fraction using UPLC/ESI(Ăą)-QTOFMS. GPC analysis shows differences in the molecular weight of the lignin samples obtained by treating bark with 1-butyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium tosylate. The use of 1-butyl-3-methylimidazolium chloride or 1-ethyl-3-methylimidazolium mesylate for the extraction of bark resulted in aromatic oligomers that are not fully soluble in the eluent used for GPC analysis. Therefore, the molecular weight as determined by GPC is only representative for the soluble part of these samples and not for the entire sample. Results obtained by investigation of the lignin samples extracted from bark using GPC and UPLC/ESI(Ăą)-QTOFMS let us conclude that 1-butyl-3-methylimidazolium acetate is the most efficient ionic liquid among the solvents investigated for the extraction of lignin from bark. The high efficiency may be attributed to a high catalytic function of this ionic liquid in bound cleavage on the one hand and an active contribution of the acetate ion to trans-esterifications on the other hand
Annotating unknown components from GC/EI-MS-based metabolite profiling experiments using GC/APCI(+)-QTOFMS
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