Maleic anhydride proton sponge as a novel MALDI matrix for the visualization of small molecules (<250 m/z) in brain tumors by routine MALDI ToF imaging mass spectrometry.

A novel vacuum stable proton sponge, 4-maleicanhydridoproton sponge (MAPS), was prepared and applied as the matrix in Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) of an aggressive brain tumor tissue (glioblastoma multiforme). Ionic maps of lactate, 2-hydroxyglutarate and chloride anions (m/z 89, 147, 35, respectively) were obtained using a routine MALDI ToF mass spectrometer.

Quantitative mapping of glycoprotein micro-heterogeneity and macro-heterogeneity: an evaluation of mass spectrometry signal strengths using synthetic peptides and glycopeptides.

Mass spectrometry has made possible the field of proteomics and become an invaluable tool for identifying and quantifying post-translational modifications of proteins from complex mixtures. Because PTMs are recognized as key factors of biological activity, reliable PTM characterization is essential to understanding the relationship between protein isoform and activity. Protein glycosylations, in particular, can be especially difficult to characterize due to the range of different oligosaccharide entities that may be attached at any particular site. In this month' Special Feature Dr Daniel Kolarich of the Dept. of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces and his collaborators point out that quantitative label-free glycoproteomics can yield information about glycoprotein microand macroheterogeniety if the tools are sufficiently accurate. To understand and characterize the performance capability of MS tools they synthesized a panel of peptides and their glycopeptide derivatives as references and used these to investigate the qualitative and quantitative results from various ionization techniques and mass analyzers.

Function of glycosyltransferase genes involved in urdamycin A biosynthesis.

BACKGROUND: Urdamycin A, the principle product of Streptomyces fradiae Tü2717, is an angucycline-type antibiotic. The polyketide-derived aglycone moiety is glycosylated at two positions, but only limited information is available about glycosyltransferases involved in urdamycin biosynthesis. RESULTS: To determine the function of three glycosyltransferase genes in the urdamycin biosynthetic gene cluster, we have carried out gene inactivation and expression experiments. Inactivation of urdGT1a resulted in the predominant accumulation of urdamycin B. A mutant lacking urdGT1b and urdGT1c mainly produced compound 100-2. When urdGT1c was expressed in the urdGT1b/urdGT1c double mutant, urdamycin G and urdamycin A were detected. The mutant lacking all three genes mainly accumulated aquayamycin and urdamycinone B. Expression of urdGT1c in the triple mutant led to the formation of compound 100-1, whereas expression of urdGT1a resulted in the formation of compound 100-2. Co-expression of urdGT1b and urdGT1c resulted in the production of 12b-derhodinosyl-urdamycin A, and co-expression of urdGT1a, urdGT1b and urdGT1c resulted in the formation of urdamycin A. CONCLUSIONS: Analysis of glycosyltransferase genes of the urdamycin biosynthetic gene cluster led to an unambiguous assignment of each glycosyltransferase to a certain biosynthetic saccharide attachment step.