PubMed · 14132704
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D JACKSON, L A BERNARD, P BENTLIT. 1964. HYPERTHYROIDISM.. https://pubmed.ncbi.nlm.nih.gov/14132704/
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A high yielding synthetic route for methyl 4'-O-methyl-beta-D-cellobioside starting from d-glucose was established. The reaction conditions optimized with nonlabeled materials were used for the synthesis of methyl 4'-O-methyl-13C12-beta-D-cellobioside, a compound having more than 99% 13C enrichment at each of the twelve pyranose carbon atoms. The labeled compound is required to study the hydrogen bond network of cellodextrins and cellulose by CPMAS NMR experiments.
Under iron-deficient conditions, the Gram-negative bacterium Pseudomonas aeruginosa ATCC 15692 secretes a peptidic siderophore, pyoverdin PaA, composed of an aromatic chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline and a partially cyclized octapeptide, D-Ser-L-Arg-D-Ser-L-FoOHOrn-(L-Lys-L-FoOHOrn-L-Thr-L-Thr) (FoOHOrn: delta N-formyl-delta N-hydroxyornithine), in which the C-terminal carboxyl group forms a peptidic bond with the primary amine of the L-Lys side chain. Ferric iron is chelated by the catechol group on the chromophore and the two hydroxyornithine side chains. In aqueous solution, the (1)H-NMR spectrum of pyoverdin PaA-Ga(III), in which Ga(III) is used instead of Fe(III) for spectroscopic purposes, showed clear evidence of exchange broadening, preventing further structural characterization. The use of cryo-solvents allowed measurements to be made at temperatures as low as 253 K where two distinct conformations with roughly equivalent populations could be observed. (13)C and (15)N labeling of pyoverdin PaA enabled complete assignment of both forms of pyoverdin PaA-Ga(III) at 253 and 267 K, using triple-resonance multidimensional NMR experiments commonly applied to doubly labeled proteins.
Recent trends in environmental remediation have increasingly employed the use of environmental chemistry techniques to decipher the source(s) and fate of the contaminants and, in some cases, to determine their age or apportion them to sources. An extensive database of pyrogenic and petrogenic 'chemical fingerprints' has been constructed by the Gas Technology Institute (GTI) and META Environmental, Inc. using gas chromatography coupled with a flame ionization detector (GC/FID) or with a mass spectrometer (GC/MS). The use of these chemical fingerprinting techniques have been highly successful in discerning wastes from wholly different sources as well as among Manufactured Gas Plant (MGP)-type wastes from different plant operations. However, these techniques have been limited when low-level polycyclic aromatic hydrocarbon (PAH) discernment is required. Specifically, these techniques often do not provide data with sufficient conclusive discriminating power between the 'urban background'PAH sources and those from MGP-operations, which is pertinent for meeting low-level, stringent site-cleanup standards. GTI has been developing a new analytical method for the measurement of 'urban background' PAH contamination. This method measures the compound-specific isotope ratio (CSIR) carbon with a GC/IRMS (isotope ratio mass spectrometer). The GC/IRMS technique is a relatively new analytical tool that has great potential as an environmental forensic method at former MGP sites. This paper focuses on the applications of both chemical and isotopic analysis of samples to discern PAH contamination in the environment.