environmental variables, including soil water content (swc), act as constraints on crop growth and productivity. therefore, open air (e0), perforated (e1) and non-perforated (e2) plastic housings were used with well-watered (w0), moderately-watered (w1) and water-stressed (w2) bush bean plants to explore the relationships between water-use efficiency (wue), carbon isotope discrimination (δ) and...

The use of stable isotope labeling has revolutionized NMR studies of nucleic acids, and there is a need for methods of incorporation of specific isotope labels to facilitate specific NMR experiments and applications. Enzymatic synthesis offers an efficient and flexible means to synthesize nucleoside triphosphates from a variety of commercially available specifically labeled precursors, permitti...

The effects of dissolved salts (NaCI, KCI, MgCl,, CaCI,, Na,SO,, MgSO,, and their mixtures) on oxygen and hydrogen isotope partitioning between brines and coexisting phases (vapor and calcite) were experimentally determined at 50-350 C and 300 C, respectively. In liquid-vapor equilibration experiments, for all of the salts studied, the hydrogen isotope fractionation factors between the salt sol...

The present review discusses the advantages and limitations of using stable-isotope tracers to assess carbohydrate and fat metabolism at the whole-body level. One advantage of stable- (v. radioactive-) isotope tracers is the relative ease with which the location of a label within a molecule can be determined using selected-ion-monitoring GC-mass spectrometry (SIM-GC-MS). This technique minimize...

Dental enamel is currently of high informative value in studies concerning childhood origin and human mobility because the strontium isotope ratio in human dental enamel is indicative of geographical origin. However, many prehistoric burials involve cremation and although strontium retains its original biological isotopic composition, even when exposed to very high temperatures, intact dental e...

Carbon isotope fractionation during aerobic mineralization of 1, 2-dichloroethane (1,2-DCA) by Xanthobacter autotrophicus GJ10 was investigated. A strong enrichment of (13)C in residual 1,2-DCA was observed, with a mean fractionation factor alpha +/- standard deviation of 0.968 +/- 0.0013 to 0.973 +/- 0.0015. In addition, a large carbon isotope fractionation between biomass and inorganic carbon...

A rapid and precise routine Pb isotope analytical technique for rock samples was developed using multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The mass discrimination of the Pb isotope ratios was corrected with the 205Tl/203Tl ratio of a Tl isotope reference material (NIST SRM 997) added to samples. The optimization of the analytical parameters and the minimizatio...

RATIONALE Because of the threat of bombings using improvised explosives containing ammonium nitrate (AN), law enforcement and intelligence communities have been interested in stable isotope techniques for tracking and discriminating AN sources. Separate analysis of the AN component ions ammonium and nitrate would add discriminatory power to these techniques. METHODS Ammonium ions in dissolved...

Compound-specific isotope analysis (CSIA) is a promising approach for tracking biotransformation of organic pollutants, but isotope fractionation associated with aromatic oxygenations is only poorly understood. We investigated the dioxygenation of a series of nitroaromatic compounds to the corresponding catechols by two enzymes, namely, nitrobenzene and 2-nitrotoluene dioxygenase (NBDO and 2NTD...

Biological reference materials with well-characterised stable isotope compositions are lacking in the field of 'isotope biochemistry', which seeks to understand bodily processes that rely on essential metals by determining metal stable isotope ratios. Here, we present Zn stable isotope data for six biological reference materials with certified trace metal concentrations: fish muscle, bovine mus...