A high-precision SIMS analysis technique has been established for oxygen, sulfur, and iron isotope ratios and applied to a wide range of geoscience research areas using a Cameca IMS-1280 at the Wisconsin Secondary Ion Mass Spectrometer Laboratory (WiscSIMS). Precision and accuracy of 0.3‰ is achieved routinely for the measurement of 18O/16O ratio using multicollection Faraday Cup (FC) detectors...

Mosses are the dominant plants in polar and boreal regions, areas which are experiencing rapid impacts of regional warming. Long-term monitoring programmes provide some records of the rate of recent climate change, but moss peat banks contain an unrivalled temporal record of past climate change on terrestrial plant Antarctic systems. We summarise the current understanding of climatic proxies an...

O-methyl substituents of aromatic compounds can provide C1 growth substrates for facultative and strict anaerobic bacteria isolated from diverse environments. The mechanism of the bioconversion of methoxylated benzoic acids to the hydroxylated derivatives was investigated with a model substrate and cultures of one anaerobic consortium, eight strict anaerobic bacteria, and one facultative anaero...

Rat liver microsomal glucose 6-phosphatase catalyses phosphoryl transfer between D-glucose 6-[(R)-16O,17O,18O]phosphate and D-glucose with retention of configuration at the phosphorus atom. Since individual phosphoryl-transfer steps appear in general to occur with inversion of configuration, this observation is most simply interpreted in terms of a double-displacement mechanism with a phosphory...

We propose a novel mechanism for isotopic exchange between CO2 and O3 via O(1D) + CO2 --> CO3* followed by CO3* --> CO2 + O(3P). A one-dimensional model calculation shows that this mechanism can account for the enrichment in 18O in the stratospheric CO2 observed by Gamo et al. [1989], using the heavy O3 profile observed by Mauersberger [1981]. The implications of this mechanism for other stra...

The stereochemical course of the phospho transfer catalyzed by homogeneous human prostatic acid phosphatase was investigated using 31P nuclear magnetic resonance spectroscopy. Transphosphorylation from phenyl-(R)-[15O, 17O, 18O]phosphate to (S)-propane-1,2-diol occurs with overall retention of configuration at phosphorus. This stereochemical result is consistent with the interpretation that the...

18F-FDG is formed through radiochemical synthesis from cyclotron-produced 18F (K. Breslow, written communication, June 2000). Production of 18F is through proton bombardment of enriched 18O-water. 18F-fluoride is bound to 1,3,4,6-tetra-O-acetyl-2-O-trifluoromethanesulfonyl-Dmannopyranose (mannose triflate) under conditions of a stereospecific second-order nucleophilic substitution reaction, whi...

3,770,720 1/1973 Butti et al. ............................ 536/24 3,829,567 8/1974 Butti et al. .. 424/18O 3,899,481 8/1975 Butti et al. ............................ 536/28 4,309,364 1/1982 Bentzen et al. . ... 54/866 4,35,950 9/1982 Sircar .............. ... 54/824 4,366,161 2/1982 Mori et al. .. ... 54/824 4,416,877 11/1983 Bentzen et al. . ... 54/824 4,450,272 5/1984. Du et al. ......... ......

North of Sahara, Algeria. The effects water/rock interactions and hydrodynamic conditions on the characteristics groundwater in Continental Intercalaire aquifer (CI) are demonstrated using hydrochemical isotopic data from Mzab Ridge. results confirm that CI oriental basin is highly mineralized (1010 > EC 3500 ?S/cm) SO4-Cl-Na type. However, it poorly (340 960) occidental predominantly belongs t...

[(S)-16O,17O]Thiophosphoenolpyruvate has been used as a substrate in H218O for the reaction catalyzed by phosphoenolpyruvate carboxylase, and the absolute configuration of the product, inorganic [16O,17O,18O]thiophosphate, has been determined. The reaction proceeds with inversion of configuration at phosphorus, thus ruling out the cyclic mechanism that has been proposed for this enzyme. The ste...