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Microcystins are a group of cyclic heptapeptides originating from cyanobacteria. Cyanobacteria also produce a range of peptides and other compounds that can result in complex chromatograms when samples are analyzed by LC-MS. Derivatization with appropriate thiols (e.g., mercaptoethanol) of the olefin in the alpha,beta-unsaturated amide present in most microcystins was shown to simplify analysis of LC-MS chromatograms of sample extracts, making it much easier to identify peaks corresponding to candidate microcystins. Furthermore, interpretation of MS2 spectra was facilitated by addition of the mass associated with the thiol to the alpha,beta-unsaturated amide of microcystins. Cyanotoxins containing Mdha or Dha reacted readily with thiols, whereas Mser, Ser, Mdhb, and thiol-derivatives of Mdha or Dha did not react under the conditions us...
Microcystins are cyclic heptapeptides from cyanobacteria which are responsible for poisonings of livestock and humans. Cyanobacteria also produce a range of peptides and other compounds that can result in complex chromatograms when samples are analysed by LC–MS. Thiol derivatization of the α,β-unsaturated amide present in most microcystins was recently shown to simplify analysis of LC–MS chromatograms of a Microcystis culture, making it easier to identify peaks corresponding to microcystins in complex mixtures. This method was applied to analysis of extracts taken from a natural cyanobacteria bloom in Mwanza Gulf, Lake Victoria, Tanzania, in 2010, revealing the presence of numerous putative microcystin analogues in the sample. Results were verified using LC–MS², LC–MS/MS with precursor-ion scanning, and LC–HRMS, leading to identificati...
Planktonic Nostocales cyanobacteria represent a challenge for microbiological research because of the wide range of cyanotoxins that they synthesize and their invasive behavior, which is presumably enhanced by global warming. To gain insight into the phylogeography of potentially toxic Nostocales from Mediterranean Europe, 31 strains of Anabaena (Anabaena crassa, A. lemmermannii, A. mendotae, and A. planctonica), Aphanizomenon (Aphanizomenon gracile, A. ovalisporum), and Cylindrospermopsis raciborskii were isolated from 14 freshwater bodies in Spain and polyphasically analyzed for their phylogeography, cyanotoxin production, and the presence of cyanotoxin biosynthesis genes. The potent cytotoxin cylindrospermopsin (CYN) was produced by all 6 Aphanizomenon ovalisporum strains at high levels (5.7 to 9.1 μg CYN mg−1 [dry weight]) with low...
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