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    ABSTRACT: Microbial communities are essential to the function of virtually all ecosystems and eukaryotes, including humans. However, it is still a major challenge to identify microbial cells active under natural conditions in complex systems. In this study, we developed a new method to identify and sort active microbes on the single-cell level in complex samples using stable isotope probing with heavy water (D2O) combined with Raman microspectroscopy. Incorporation of D2O-derived D into the biomass of autotrophic and heterotrophic bacteria and archaea could be unambiguously detected via C-D signature peaks in single-cell Raman spectra, and the obtained labeling pattern was confirmed by nanoscale-resolution secondary ion MS. In fast-growing Escherichia coli cells, label detection was already possible after 20 min. For functional analyses of microbial communities, the detection of D incorporation from D2O in individual microbial cells via Raman microspectroscopy can be directly combined with FISH for the identification of active microbes. Applying this approach to mouse cecal microbiota revealed that the host-compound foragers Akkermansia muciniphila and Bacteroides acidifaciens exhibited distinctive response patterns to amendments of mucin and sugars. By Raman-based cell sorting of active (deuterated) cells with optical tweezers and subsequent multiple displacement amplification and DNA sequencing, novel cecal microbes stimulated by mucin and/or glucosamine were identified, demonstrating the potential of the nondestructive D2O-Raman approach for targeted sorting of microbial cells with defined functional properties for single-cell genomics.
    Full-text · Article · Dec 2014 · Proceedings of the National Academy of Sciences
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    ABSTRACT: The reaction of acetylide anions with carbon disulfide or phenyl isothiocyanate followed by addition of sulfur in the presence of a protonating agent such as a primary amine or alcohol affords 1,2-dithiole-3-thiones or 3-imino-1,2-dithioles in good to excellent yields.
    No preview · Article · Sep 2014 · Tetrahedron Letters
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    ABSTRACT: Xanthine, caffeine and three isomeric dimethyl xanthines (theobromine, theophylline and paraxanthine) are often described as aromatic on various criteria. Here we complete the picture by assessing these molecules for aromaticity on the ring-current criterion. Magnetic response calculations are performed at the B3LYP and CHF/6-31G** ipsocentric levels of theory on structures optimised at the B3LYP/6-31G** level. All five systems display consistent pi-electron ring-currents delocalised around the imidazole moiety in all cases; these are accompanied by localised features on the six-membered rings attributed to nitrogen and oxygen 'lone-pair' pi-electron circulations. All are therefore aromatic on the magnetic criterion, with a 'locally delocalised' ring current in the imidazole moiety, similar to those in the isolated imidazole and methylimidazole molecules.
    No preview · Article · Mar 2014 · Tetrahedron Letters
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