title: Isolation and purification of Cu-free methanobactin from Methylosinus trichosporium OB3b.
abstract: BACKGROUND
  The isolation of highly pure copper-free methanobactin is a prerequisite for the investigation of the biogeochemical functions of this chalkophore molecule produced by methane oxidizing bacteria. Here, we report a purification method for methanobactin from Methylosinus trichosporium OB3b cultures based on reversed-phase HPLC fractionation used in combination with a previously reported resin extraction. HPLC eluent fractions of the resin extracted product were collected and characterized with UV-vis, FT-IR, and C-1s NEXAFS spectroscopy, as well as with elemental analysis and ESI-MS.
  
  
  RESULTS
  The results showed that numerous compounds other than methanobactin were present in the isolate obtained with resin extraction. Molar C/N ratios, mass spectrometry measurements, and UV-vis spectra indicated that methanobactin was only present in one of the HPLC fractions. On a mass basis, methanobactin carbon contributed only 32% to the total organic carbon isolated with resin extraction. Our spectroscopic results implied that besides methanobactin, the organic compounds in the resin extract comprised breakdown products of methanobactin as well as polysaccharide-like substances.
  
  
  CONCLUSIONS
  Our results demonstrate that a purification step is indispensable in addition to resin extraction in order to obtain pure methanobactin. The proposed HPLC purification procedure is suitable for semi-preparative work and provides copper-free methanobactin.
authors.affiliation: Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Sciences, ETH Zurich, CHN, Universitätstrasse 16, 8092 Zurich, Switzerland. iso.christl@env.ethz.ch.
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Pesch
authors.forename: Iso
authors.initials: I
authors.lastname: Christl
authors.forename: Kurt
authors.initials: K
authors.lastname: Barmettler
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Kraemer
authors.forename: Ruben
authors.initials: R
authors.lastname: Kretzschmar