Abstract. Isotope-based approaches to study plant water sources rely on the assumption that root uptake and within-plant transport are non-fractionating processes. However, a growing number of studies have reported offsets between source stable isotope composition for wide range ecosystems. These isotopic can result in erroneous attribution used by plants potential overestimations groundwater v...

Isotope selective effects in resonance ionization mass spectrometry (RIMS) pose a potentially serious limitation to the application of this technique to the precise and reproducible measurement of isotope ratios. In order to identify some of the underlying causes of isotope selectivity in RIMS and to establish procedures for minimizing these effects, we investigated laser-induced isotope select...

Stable hydrogen isotope ratios (?2H values) in structural hydroxyl groups of pedogenic clay minerals are inherited from the surrounding water at time their formation. Only non-exchangeable H preserves environmental forensic and paleoclimate information (?2Hn value). To measure ?2Hn values soil fractions, we adapted a steam equilibration method by accounting for high hygroscopicity. Our USGS57 b...

The L-lactate-flavocytochrome b2-ferricyanide electron-transfer system from the yeast Hansenula anomala was investigated by rapid-reaction techniques. The kinetics of reduction of oxidized flavocytochrome b2 by L-lactate and L-[2H]lactate were biphasic both for flavin and haem prosthetic groups and at all concentrations tested. The first-order rate constants of the rapid and slow phases depende...

MOTIVATION Using stable isotopes in global proteome scans, labeled molecules from one sample are pooled with unlabeled molecules from another sample and subsequently subjected to mass-spectral analysis. Stable-isotope methodologies make use of the fact that identical molecules of different stable-isotope compositions are differentiated in a mass spectrometer and are represented in a mass spectr...

The isotopic composition, e.g. 14C/12C, 13C/12C, 2H/1H, 15N/14N and 18O/16O, of matter elements is heterogeneous. It is ruled by physical, chemical and biological mechanisms. Isotopes thus be enable to follow the fate of mineral and organic compounds during biogeochemical transformations. The determination of the isotopic composition of organic substances occurring at trace level into very comp...

Many enzymes catalyze N-dealkylations of alkylamines, including cytochrome P450 (P450) and peroxidase enzymes. Peroxidases, exemplified by horseradish peroxidase (HRP), are generally accepted to catalyze N-dealkylations via 1-electron transfer processes. Several lines of evidence also support a 1-electron mechanism for many P450 reactions, although this view has been questioned in light of repo...

These compounds display in the 1H NMR spectrum a low field triplet at δ 7.08, due to the alkene H-9 proton experiencing the diamagnetic anisotropy effect of the adjacent nitro group. This chemical shift value also indicates the cis arrangement of the double bond. Another salient signal is represented by a 2H doublet at δ  3.33/3.27, due to the bisallylic methylene protons flanked by the nitro ...

Significant air temperature and precipitation changes have occurred since the 2000s in vulnerable Siberian subarctic regions urged updates of available chronologies towards third millennium. It is important to better understand recent climatic compared past decades, centuries even millennia. In this study, we present first annually resolved triple tree-ring isotope dataset (?13C, ?18O ?2H) for ...