Solvent deuterium isotope effects support the view that the p-N02 and p-Me derivatives of benzaldehyde S.S-diethylacetal undergo silver ion-promoted hydrolysis in water by different mechanisms. scheme common [3] for O.O-acetals in the presence of H30 + ions, while for the latter we suggested a bimolecular A2-type mechanism with one (or more) water molecules in the slow phase of step (3). The co...

The combination of high-resolution LC-MS-based untargeted metabolomics with stable isotope tracing provides a global overview of the cellular fate of precursor metabolites. This methodology enables detection of putative metabolites from biological samples and simultaneous quantification of the pattern and extent of isotope labeling. Labeling of Trypanosoma brucei cell cultures with 50% uniforml...

Oxygen-isotope ratios of a stalagmite from Socotra Island in the Indian Ocean provide a record of changes in monsoon precipitation and climate for the time period from 42 to 55 thousand years before the present. The pattern of precipitation bears a striking resemblance to the oxygen-isotope record from Greenland ice cores, with increased tropical precipitation associated with warm periods in th...

The metabolic products of propionate metabolism in man were studied by determining the pattern of isotope in the urine following the intravenous injection of [lJ%]propionate. A major peak of radioactivity not present in control subjects was found in an organic acid in two patients with propionic acidemia and a patient with methylmalonic acidemia. This labeled compound was characterized as methy...

[1] Oxygen and carbon stable-isotope compositions of modern benthic foraminifera in the Kara and Pechora estuarine regions of the Arctic continental shelf were compared with water dO, dCDIC, temperature, and salinity. The foraminiferal dO distribution is mostly similar to that of equilibrium calcite, primarily controlled by mixing of runoff and seawater in near-estuarine areas (depth < 15–20 m)...

Metabolic flux analysis (MFA) has so far been restricted to lumped networks lacking many important pathways, partly due to the difficulty in automatically generating isotope mapping matrices for genome-scale metabolic networks. Here we introduce a procedure that uses a compound matching algorithm based on the graph theoretical concept of pattern recognition along with relevant reaction informat...

Isotope clusters in library electron ionization mass spectra of germanes often appear a few u lower than theoretically expected from elemental composition; for example, the dominant peak of the Ge(4)H(10)(+) pattern is shifted 8 u down. This phenomenon is due to combinations of three essential components: the molecular ion Ge(n)H(2n+2)(+) and two products of hydrogen elimination, Ge(n)H(+) and ...

Kinetic isotope effects (V/K) were measured with AMP nucleosidases isolated from Azotobacter vinelandii, from a Vmax mutant enzyme of A. vinelandii and from Escherichia coli. Specifically labeled AMP substrates were used to measure 3H secondary and 14C primary kinetic isotope effects on the N-glycosidic bond hydrolysis of AMP in the presence and absence of the allosteric activator, MgATP. Use o...

The determination of compound-specific stable isotope ratios is a promising new tool to assess biodegradation of organic compounds in groundwater. In this study, the occurrence of carbon isotope fractionation during dechlorination of tetrachloroethene (PCE) to ethene was evaluated in a PCE-contaminated aquifer and in a microcosm that was based on aquifer material from the site. In the microcosm...