The degradation of organic micropollutants occurs via different reaction pathways. Compound specific isotope analysis is a valuable tool to identify such degradation pathways in different environmental systems. We propose a mechanism-based modeling approach that provides a quantitative framework to simultaneously evaluate concentration as well as bulk and position-specific multi-element isotope...

catalyzed by glycogen synthase D (UDP-glucose:glycogen o-4-glucosyltransferase, EC 2.4.1.11) was studied, using r4C isotope transfer rates. The reaction rates were determined at varying concentrations of either substrate at constant amounts of the other substrate. The inhibition patterns of UDP as well as the activation patterns of the activator glucose 6-phosphate toward either substrate were ...

MOTIVATION High-resolution mass spectrometry (MS) is among the most widely used technologies in metabolomics. Metabolites participate in almost all cellular processes, but most metabolites still remain uncharacterized. Determination of the sum formula is a crucial step in the identification of an unknown metabolite, as it reduces its possible structures to a hopefully manageable set. RESULTS ...

Whole-plant and leaf nitrogen isotope composition are determined by the isotope ratio of the external nitrogen source and physiological mechanisms within the plant. Whole-plant isotope composition can reflect that of the nitrogen source when plant demand exceeds nitrogen supply. Uptake by mycorrhizae can cause the isotope ratio of the plant to deviate from the source. Intra-plant variation in i...

PURPOSE Several isotopes are available for low dose-rate brachytherapy of the prostate. Currently, most implants use a single isotope. However, the use of dual-isotope implants may yield an advantageous combination of characteristics such as half-life and relative biological effectiveness. However, the use of dual-isotope implants complicates treatment planning and quality assurance. Do the ben...

Introduction: Evidence for isotope anomalies in primitive chondrites, and in iron meteorites, have been reported in Mo [1,2], Ru [3], Ba [4], Nd [5, 6], and Sm [6]. Osmium is a highly refractory element for which isotopic anomalies in bulk chondrites or differentiated meteorites have not been reported, yet. Brandon et al. [7] reported Os isotope anomalies in primitive chondrites, with the large...

Organic compounds are produced in vast quantities for industrial and agricultural use, as well as for human and animal healthcare [1]. These chemicals and their metabolites are frequently detected at trace levels in fresh water environments where they undergo degradation via different reaction pathways. Compound specific stable isotope analysis (CSIA) is a valuable tool to identify such degrada...

The intramolecular (13)C kinetic isotope effects for the ring-opening of cyclopropylcarbinyl radical were determined over a broad temperature range. The observed isotope effects are unprecedentedly large, ranging from 1.062 at 80 degrees C to 1.163 at -100 degrees C. Semiclassical calculations employing canonical variational transition-state theory drastically underpredict the observed isotope ...

The interpretation of stable isotope values hinges on precise, accurate estimates of kinetic isotope effects ( ), which are equal to k/k, where k and k are the reaction rate constants for the two isotopes. Kinetic isotope effects are commonly determined by monitoring the reactant concentration (C) and isotope ratio (R) relative to their initial values (C1 and R1, respectively). Values of are es...

the lut block (eastern iran) extends over 900 km in a north-south direction and is only 200 km wide in an east-west direction. it is confined by the nayband fault and shotori range on the west. the eastern edge is bordered by the sistan suture zone and nehbandan fault. the northern termination of lut block is the depression of kavir-e-namak and the great kavir fault. the makran arc, including t...