Isotope ratios of cellulose and cellulose nitrate from aquatic Crassulacean acid metabolism (CAM) and non-CAM plants were determined. Cellulose oxygen istope ratios for all plants that grew together were virtually identical, whereas large differences were observed for hydrogen isotope ratios of cellulose nitrate between CAM and non-CAM plants. Carbon isotope ratios of cellulose nitrate did not ...

The precise interpretation of environmental sulfur isotope records requires a quantitative understanding of the biochemical controls on sulfur isotope fractionation by the principle isotope-fractionating process within the S cycle, microbial sulfate reduction (MSR). Here we provide the only direct observation of the major ((34)S/(32)S) and minor ((33)S/(32)S, (36)S/(32)S) sulfur isotope fractio...

Photosynthetic carbon isotope discrimination is a non-destructive tool for investigating C4 metabolism. Tuneable diode laser absorption spectroscopy provides new opportunities for making rapid, concurrent measurements of carbon isotope discrimination and CO2 assimilation over a range of environmental conditions, and this has facilitated the use of carbon isotope discrimination as a probe of C4 ...

OBJECTIVE Cartilage invasion in laryngohypopharyngeal cancer has a significant impact on the choice of treatment modality and outcome of the disease. We examined invasion of cartilage in laryngohypopharyngeal cancer by simultaneous bone and tumor dual-isotope SPECT using 99mTc-hydroxymethylene diphosphonate and 201Tl-chloride. METHODS Early and delayed simultaneous bone and tumor dual-isotope...

OBJECTIVE Lead poisoning can, in some cases, be traced to a specific route or source of exposure on the basis of the individual's blood lead isotope ratio. To assess the major source of lead exposure among women residing in Mexico City, we compared blood, ceramic, and gasoline lead isotope ratios. MATERIAL AND METHODS The study population, randomly selected from participants of a large trial,...

Stable isotope analysis (SIA; carbon, hydrogen, nitrogen, sulfur, and oxygen) of human tissues offers a means for assessing diet among living humans. Stable isotope ratios of broad categories of food and drink food vary systematically, and stable isotope ratios in consumer tissues represent a composite of the isotopic ratios of food and drink consumed during an individual's life. Isotopic evide...

The mechanism of the ene reaction of singlet ((1)delta(g)) oxygen with simple alkenes is investigated by a combination of experimental isotope effects and several levels of theoretical calculations. For the reaction of 2,4-dimethyl-3-isopropyl-2-pentene, the olefinic carbons exhibit small and nearly equal (13)C isotope effects of 1.005-1.007, while the reacting methyl groups exhibit (13)C isoto...

A procedure for Stable Isotope Dilution Analysis in molecular Mass Spectrometry which does not require a methodological calibration graph and can be applied in combination with minimal labelling has been evaluated. This alternative approach is based on the determination of the molar fractions for each pure isotope pattern (natural abundance or labelled) contributing to the isotope pattern obser...

In higher eukaryotes many genes encode protein isoforms whose properties and biological roles are often poorly characterized. Here we describe systematic approaches for detection of either distinct isoforms, or separate pools of the same isoform, with differential biological properties. Using information from ion intensities we have estimated protein abundance levels and using rates of change i...

A compact isotope ratio laser spectrometry (IRLS) instrument was developed for simultaneous measurements of the D/H, 18O/16O and 17O/16O isotope ratios in water by laser absorption spectroscopy at 2.73 μm. Special attention is paid to the spectral data processing and implementation of a Kalman adaptive filtering to improve the measurement precision. Reduction of up to 3-fold in standard deviati...