Nuclear Magnetic Resonance Spectrometry (NMR)
(This instrument is now operated independently of the OMS Facility but Carl Johnson remains the contact for its use.)
Natural occurrence of polyhalogenated diphenyl ethers, E. L. Teuten 2005
Bioaccumulation of persistent chlorinated environmental contaminants (ex. PCBs and DDT) through the trophic levels was been widely reported for years. More recently, polybrominated diphenyl ethers (PBDEs, widely used as flame retardants) and related methoxylated-PBDEs (MeO-PBDEs)have been reported in human and animal tissue. While the simple assumption is that anthropogenic PBDEs are the source of this contamination, certain sponges(Dysidea herbacea and D. dendyi) as well as a green algae (Cladophora fascicularis) are also know to produce MeO-PBDEs. Postdoctoral scholar Dr. Emma Teuten isolated these materials from a True's beaked whale (Mesoplodon mirus), and confirmed their exact structures and identities with data from the Autospec-Q and Avance 400 NMR (Teuten et al., 2006) and proceeded demonstrate by radiocarbon dating that at least in certain cases, these brominated compounds were of natural origin (Teuten et al., 2005).
Identification of a novel alkenone, L. Xu 2001
Alkenones of differing carbon chain length are also know. Mr. Li Xu et al. discovered a C36 alkenone in sediments from the Black Sea. Full identification of this new compound involved Autospec-Q high resolution MS to determine the exact elemental composition, Avance 400 NMR 1H, 13C, DEPT and HETCOR experiments to determine the exact conformation. Compound specific 13C GC-irMS analysis on the DeltaPlus showed two distinct zones of C36 alkenone production; a recent zone where the new compound had a d13C ratio very similar to the typical C37 alkenones, and a more ancient zone where the ratio was much higher suggesting production from a different biological source (Xu et al., 2001).
Extracellular enzymatic degradation of polysaccharides, C. Arnosti 1994
Some fraction DOM/DOC is believed to be derived from polysaccharides of various sources. Dr. Carol Arnosti made extensive use of the Facility’s AC-300 NMR spectrometer to follow the extracellular bacterial enzymatic degradation of polysaccharides [ref], specifically using pullulan as a model compound and showing that this hydrolysis occurred far more rapidly than had previously been accepted [ref]. She also reported numerous corrections to the accepted 1H and 13C assignments of pullulan and isomaltose [ref].
Some fraction DOM/DOC is believed to be derived from polysaccharides of various sources. Dr. Carol Arnosti made extensive use of the Facility’s AC-300 NMR spectrometer to follow the extracellular bacterial enzymatic degradation of polysaccharides [ref], specifically using pullulan as a model compound and showing that this hydrolysis occurred far more rapidly than had previously been accepted [ref]. She also reported numerous corrections to the accepted 1H and 13C assignments of pullulan and isomaltose [ref].