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PubMed1985

Radiometric analysis of oxidative reactions in aromatization by placental microsomes. Presence of differential isotope effects.

In order to study the initial as well as the final steps in the aromatization of androgens to estrogens, high-specific activity [19-C3H3]androstenedione and testosterone were synthesized. Incubations of [19-C3H3]androstenedione with human placental microsomes resulted in the generation of [3H]water, as a result of the dual hydroxylation at C-19, and [3H]formic acid reflecting final aromatization. After an initial lag in the production of [3H]formic acid, the two radiolabeled products were formed linearly with time at a ratio of 2 to 1 under subsaturating conditions and 2.2 to 1 when saturating levels of substrate were present. Incubation of a mixture of [19-C3H3]- and [4-14C]androstenedione with human placental microsomes yielded 19-hydroxy- and 19-oxoandrostenedione, respectively, products of one and two hydroxylations at C-19. The isotope ratios of these derivatives revealed the presence of a tritium isotope effect in the first but not in the second hydroxylation at that site. When [19-C3H2]- and [4-14C]19-hydroxyandrostenedione were used as the substrate, the isotope ratio of the isolated 19-oxoandrostenedione showed no evidence of any isotope effect in its formation. Thus, the second hydroxylation at C-19 exhibits no isotope effect irrespective of whether androstenedione or 19-hydroxyandrostenedione are the substrates, and therefore, a concerted process and catalytic commitment are not responsible for the difference in isotope effects between the first and second C-19 hydroxylation by the placental aromatase complex. Radiometric kinetic analysis employing [19-C3H3]- and [1 beta,2 beta-3H]androstenedione as the comparative substrates provided evidence that the isotope effect is exerted solely through the Vmax component of the reaction. The distinction between the successive hydroxylations at C-19 in the aromatization sequence suggests, but does not prove, that different mechanisms, and hence different catalytic sites, may be involved in these steps.

Androstenedione↗
PubMed1993

Evidence for specific base catalysis in N-dealkylation reactions catalyzed by cytochrome P450 and chloroperoxidase. Differences in rates of deprotonation of aminium radicals as an explanation for high kinetic hydrogen isotope effects observed with peroxidases.

Alkylamines are oxidized by a number of different types of enzymes, and the low oxidation potentials favor 1-electron transfer processes and aminium radicals. We studied the mechanism of N-dealkylation by hemoproteins using the prototypic substrate N,N-dimethylaniline (with isotopic substitution on the methyl groups), since there were considerable data available from kinetic deuterium isotope studies suggesting alternative mechanisms for different hemoproteins (Miwa, G.T., Walsh, J.S., Kedderis, G.L., and Hollenberg, P. F. (1983) J. Biol. Chem. 258, 14445-14449). Cytochrome P450 2B1 (P450), chloroperoxidase, and several biomimetic metalloporphyrin systems showed low kinetic hydrogen isotope effects (D(V/K)intra < or = 2.0, T(V/K) < or = 3.4), and hemoglobin, horseradish peroxidase, and prostaglandin H synthase yielded high isotope effects (D(V parallel K)intra > or = 3.5, T(V/K) > or = 8.1), in agreement with previous studies. Dinnocenzo and Banach (Dinnocenzo, J. P., and Banach, T. E. (1989) J. Am. Chem. Soc. 111, 8646-8653) have provided evidence that the pKa for an alpha-hydrogen of the N,N-dimethylaniline aminium radical is approximately 9 and also estimated that the pKa for the 4-hydrogen of a 1,4-dihydropyridine aminium radical is approximately 3.5. The oxidations of two model 1,4-dihydropyridines showed only low kinetic hydrogen isotope effects with all of the enzymes examined (D(V/K) < or = 2.3, T(V/K) < or = 2.8). Aminium radicals derived from aminopyrine and N,N-dimethylthioanisole accumulated only with those hemoprotein systems showing the high isotope effects with N,N-dimethylaniline. We conclude that specific base catalysis of alkyl hydrogen removal from aminium radicals by the (Fe.O)2+ complex is a feature of some hemoproteins, including P450s, and that the lack of such catalysis in other hemoproteins is the basis of their high kinetic hydrogen isotope effects.

Alkylation↗
PubMed1996

Stable carbon and nitrogen isotopic composition of diet and hair of Gidra-speaking Papuans.

The carbon and nitrogen stable isotopic composition of the scalp hair and diet of Gidra-speaking people in four villages in Papua New Guinea is presented. The isotopic composition of hair was measured, while that of the diet was estimated from food consumption survey data and the measured isotopic composition and protein and carbohydrate contents of food items. The average isotopic ratios of the hair samples and of the diet varied among the four study villages, which were selected because of their diverse ecological settings. Comparison was made between hair and calculated dietary isotopic compositions. Two of the four diet-hair enrichment values obtained for 13C (+1.8 and 2.2%) were similar to those previously reported (1.4-2.0%), but the other two values (3.7 and 4.8%) were greater than in earlier reports. 15N enrichment was systematically greater (by 1.0%) than reported values (4.3%) except for one village, where a much greater enrichment (6.9%) was found. The factors potentially relevant to these deviations are discussed. Possible errors in estimating the dietary isotopic composition and minor modifications of dietary habits revealed by food consumption surveys could explain most of the discrepancies. However, the great enrichment of 15N found in one of the villages remains unexplained.

Adult↗
PubMed1997

Stable isotopic analysis of human diet in the Marianas Archipelago, western Pacific.

Proportions of marine vs. terrestrial resources in prehistoric human diets in the southern Mariana Islands (Guam, Rota, Saipan), Micronesia, have been estimated by analysis of stable isotope ratios of carbon and nitrogen in bone collagen and of carbon in apatite. The isotopic composition of marine and terrestrial food resources from the Marianas have also been determined. Experimental evidence shows that collagen carbon isotopes mainly reflect those of dietary protein sources and thus overestimate the contribution of marine animal foods. Marine protein consumption apparently ranges from approximately 20% to approximately 50% on these islands. Experiments also demonstrate the carbon isotope ratio of bone apatite carbonate accurately reflects that of the whole diet. Carbonate carbon isotope data suggest some individuals consumed significant amounts of 13C-enriched (C4) plants or seaweeds. Sugar cane is an indigenous C4 crop and seaweeds are eaten throughout the Pacific, but they have not been considered by archaeologists to have been prehistoric dietary staples. Apatite carbon isotope analysis has apparently identified previously unrecognized prehistoric dietary adaptations in the Mariana Islands, but this must be confirmed by archaeobotanical evidence.

Bone and Bones↗
PubMed2005

Using stable isotope analysis to obtain dietary profiles from old hair: a case study from Plains Indians.

Stable isotope composition of human tissue reflects that of foods consumed, and can provide information about diet independent of artifactual remains. Here we refine and test this method by analyzing nitrogen (delta(15)N) and carbon (delta(13)C) isotope ratios in historic North American Plains Indians hair. Gas-source isotope-ratio mass spectrometry provides high-precision data for both delta(15)N and delta(13)C (+/-0.2 per thousand, 1 sigma) in single hair strands as short as 2 cm (100-150 mug). Because hair contains more carbon than nitrogen, if only delta(13)C data are needed, shorter strands (<1 cm) can be analyzed. This reduction in sample size opens new opportunities for analysis of small hair fragments found in archaeological excavations, as well as for analysis of seasonal variations in long hair strands. We find distinct isotope profiles (delta(15)N vs. delta(13)C) for two cultural groups, the Lower Brule reservation Sioux of 1892 and the reservation Blackfoot of 1892 and 1935. The resultant dietary profiles indicate a higher consumption of meat by the Blackfoot and a higher consumption of maize (or of animals that had fed on maize or other C(4) plants) by the Lower Brule. The two groups of Blackfoot yield similar isotopic profiles despite the passage of four decades, suggesting a strong role for cultural preference even as food sources change. Such stable isotope profiles can be used to link samples from the same cultural tradition based on their similar diets.

Carbon Isotopes↗
PubMed2003

Reconstruction of the isotopic history of animal diets by hair segmental analysis.

Carbon and nitrogen isotope signatures (delta(13)C and delta(15)N) of animal tissues provide information about the diet and, hence, the environment in which the animals are living. Hair is particularly useful as it provides a stable archive of temporal (e.g. seasonal) fluctuations in diet isotope composition. It can be sampled easily and with minimal disturbance from living subjects. However, derivation of the temporal record along the hair length may be subject to errors and uncertainties. This study investigates (and suggests means to minimize) several sources of error, including (a) incomplete sampling, (b) sampling during the quiescent (telogen) phase, (c) non-representative sub-sampling, (d) ignorance of hair growth rate, i.e. time-position relationship of isotope signatures, and (e) non-optimal compromise between analytical/procedural precision and effort/cost. Cattle tail switch hair was collected from animals of different breed, sex and age. Hair was washed, sectioned, and 5- or 10-mm-long sections were analyzed for C and N isotope composition. Signatures along paired hairs were similar (r(2) approximately 0.8) and distances between isotopic minima and maxima nearly identical, indicating that a single hair constituted a representative sample and (except for telogen hair) hair growth rate was the same for paired hairs. However, cutting hair, instead of plucking, caused a variable loss of recently grown hair and information. Telogen hair was identified and data loss due to cutting error reduced when more than one hair from the same animal and sampling region was compared to spot and delimit common and missing regions. Similarly, comparison of isotopic profiles from hair collected at different times identified the segment produced during the respective interval and allowed calculation of average hair growth rate, which varied between animals (0.69-1.06 mm d(-1)). Analysis of alternate 10-mm-long sections for two hairs per animal provided a good compromise between precision/resolution and effort. The method should be applicable to other mammalian species including man.

Aging↗
PubMed2004

A new concept for isotope ratio monitoring liquid chromatography/mass spectrometry.

A new interface for the on-line coupling of a liquid chromatograph to a stable isotope ratio mass spectrometer has been developed and tested. The interface is usable for (13)C/(12)C determination of organic compounds, allowing measurement of small changes in (13)C abundance in individual analyte species. All of the carbon in each analyte is quantitatively converted into CO(2) while the analyte is still dissolved in the aqueous liquid phase. This is accomplished by an oxidizing agent such as ammonium peroxodisulfate. The CO(2) is separated from the liquid phase and transferred to the mass spectrometer. It is shown that the whole integrated process does not introduce isotope fractionation. The measured carbon isotope ratios are accurate and reproducible. The sensitivity of the complete system allows isotope ratio determination down to 400 ng of compound on-column. By-passing the high-performance liquid chromatography (HPLC) separation allows bulk isotopic analysis with substantially lower sample amounts than those required by conventional elemental analyzers. The results of the first applications to amino acids, carbohydrates, and drugs, eluted from various types of HPLC columns, are presented. The wide range of chromatographic methods enables the analysis of compounds never before amenable to isotope ratio mass spectrometry techniques and may lead to the development of many new assays.

Carbon Dioxide↗
PubMed2003

Spatial analysis of stable isotope data to determine primary sources of nutrition for fish.

Carbon and nitrogen stable isotopes were used to determine the ultimate autotrophic sources supporting production of three commercially important fish species over unvegetated mudflats in a subtropical estuary. Mean isotope values over the whole estuary for fish and autotroph sources were modeled to indicate feasible combinations of sources. Variability in isotope values among nine locations (separated by 3-10 km) was then used as a further test of the likelihood that sources were involved in fish nutrition. A positive spatial correlation between isotope values of a fish species and an autotroph indicates a substantial contribution from the autotroph. Spatial correlations were tested with a newly developed randomization procedure using differences between fish and autotroph values at each location, based on carbon and nitrogen isotopes combined in two-dimensional space. Both whole estuary modeling and spatial analysis showed that seagrass, epiphytic algae and particulate organic matter in the water column, including phytoplankton, are likely contributors to bream (Acanthopagrus australis) nutrition. However, spatial analysis also showed that mangroves were involved (up to 33% contribution), despite a very low contribution from whole estuary modeling. Spatial analysis on sand whiting (Sillago ciliata) demonstrated the importance of two sources, mangroves (up to 25%) and microalgae on the mudflats, considered unimportant based on whole estuary modeling. No spatial correlations were found between winter whiting (Sillago maculata) and autotrophs, either because fish moved among locations or relied on different autotrophs at different locations. Spatial correlations between consumer and source isotope values provide a useful analytical tool for identifying the role of autotrophs in foodwebs, and demonstrated here that both in situ production of microalgae and organic matter from adjacent habitats were important to fish over mudflats.

Animals↗
PubMed2005

A test of geographic assignment using isotope tracers in feathers of known origin.

We used feathers of known origin collected from across the breeding range of a migratory shorebird to test the use of isotope tracers for assigning breeding origins. We analyzed deltaD, delta13C, and delta15N in feathers from 75 mountain plover (Charadrius montanus) chicks sampled in 2001 and from 119 chicks sampled in 2002. We estimated parameters for continuous-response inverse regression models and for discrete-response Bayesian probability models from data for each year independently. We evaluated model predictions with both the training data and by using the alternate year as an independent test dataset. Our results provide weak support for modeling latitude and isotope values as monotonic functions of one another, especially when data are pooled over known sources of variation such as sample year or location. We were unable to make even qualitative statements, such as north versus south, about the likely origin of birds using both deltaD and delta13C in inverse regression models; results were no better than random assignment. Probability models provided better results and a more natural framework for the problem. Correct assignment rates were highest when considering all three isotopes in the probability framework, but the use of even a single isotope was better than random assignment. The method appears relatively robust to temporal effects and is most sensitive to the isotope discrimination gradients over which samples are taken. We offer that the problem of using isotope tracers to infer geographic origin is best framed as one of assignment, rather than prediction.

Animal Migration↗
PubMed1991

Isotopic analyses of amino acids from the Murchison meteorite.

Previous isotopic analyses of the total amino acids of the Murchison meteorite showed these compounds to be substantially enriched in 2H, 13C, and 15N relative to terrestrial organic matter. These analyses have been repeated (2H, 13C) with inclusion of an ultrafiltration step to exclude the possibility that a fine particulate contaminant carried the isotopic excesses observed in the previous work. In addition, the meteorite amino acids were chromatographically separated to rule out the possibility that the isotopic enrichment of the meteorite extract could reside in basic compounds other than amino acids. The results indicate that the Murchison amino acids are truly isotopically unusual, that the isotopic excesses reside in at least several different amino acids, and that the isotopic contents of some of these amino acids reach values of about +40% (delta 13C) and +2500% (delta D). If it is assumed that the high deuterium content of the meteorite alpha-amino acids is a result of the synthesis of their molecular precursors by low temperature ion-molecule reactions in an interstellar cloud, their formation by aqueous phase Strecker reactions in the parent body is consistent with their general characteristics and with known parent body processes.

Amino Acids↗
PubMed2003

Stable hydrogen, carbon and chlorine isotope measurements of selected chlorinated organic solvents.

Stable hydrogen isotopes of two chlorinated solvents, trichloroethylene (TCE) and 1,1,1-trichloroethane (TCA), provided by five different manufacturers, were determined and compared to their carbon and chlorine isotopic signatures. The isotope ratio for delta2H of different TCEs ranged between +466.9 per thousand and +681.9 per thousand, for delta13C between -31.57 per thousand and -27.37 per thousand, and for delta37Cl between -3.19 per thousand and +3.90 per thousand. In the case of the TCAs, the isotope ratio for delta2H ranged between -23.1 per thousand and +15.1 per thousand, for delta13C between -27.39 per thousand and -25.84 per thousand, and for delta37Cl between -3.54 per thousand and +1.39 per thousand. As well, a column experiment was carried out to dechlorinate tetrachloroethylene (PCE) to TCE using iron. The dechlorination products have completely different hydrogen isotope ratios than the manufactured TCEs. Compared to the positive values of delta2H in manufactured TCEs (between +466.9 per thousand and +681.9 per thousand), the dechlorinated products had a very depleted delta2H (less than -300 per thousand). This finding has strong implications for distinguishing dechlorination products (PCE to TCE) from manufactured TCE. In addition, the results of this study show the potential of combining 2H/1H analyses with 13C/12C and 37Cl/35Cl for isotopic fingerprinting applications in organic contaminant hydrogeology.

Carbon Isotopes↗
PubMed1987

The use of stable isotopes in metabolic investigation.

The use of tracers to define substrate dynamics has been the sine qua non of metabolic investigation in vivo, because static measurements of substrate content alone are inadequate. The judicious use of radioactively labelled compounds remains the principal tracer approach in some adult subjects. However, in certain young adults, in pregnant women and in children, stable isotope tracers offer a practical alternative for answering important metabolic questions. In the last decade, the developmental problems previously associated with employing stable isotope tracers for this purpose have largely disappeared. Furthermore, the use of stable isotopically labelled materials offers certain additional advantages which are either difficult or impossible to achieve using radiotracers. These include the ability to measure simultaneously substrate content and isotopic enrichment with very high specificity and precision, the ability to determine the intramolecular location of the label, the ability to use the mass of the stable isotope substrate as a probe of the metabolite system response to perturbation, and the ability to study simultaneously and repeatedly the same subject with multiple substrate tracers. The practical application of these principles has been amply demonstrated by the expanding use of non-radioactive tracers to study body composition, energy balance, and the inter-organ transport and oxidation of the three major metabolic fuels--glucose, fat and amino acids. Continued development in the organic synthesis of new, stable isotopically labelled biochemicals will allow investigation of additional areas of biomedical importance which have been hitherto inaccessible to this approach, particularly in the pathophysiology of metabolic events in the growing child.

Body Composition↗
PubMed1988

Isotope effect studies of the chemical mechanism of pig heart NADP isocitrate dehydrogenase.

The catalytic mechanism of porcine heart NADP isocitrate dehydrogenase has been investigated by use of the variation of deuterium and 13C kinetic isotope effects with pH. The observed 13C isotope effect on V/K for isocitrate increases from 1.0028 at neutral pH to a limiting value of 1.040 at low pH. The limiting 13C isotope effect with deuteriated isocitrate at low pH is 1.016. This decrease in 13(V/KIc) upon deuteriation indicates a stepwise mechanism for the oxidation and decarboxylation of isocitrate. This predicts a deuterium isotope effect on V/K of 2.9, but D(V/K) at low pH only increases to a maximum of 1.08. It is not known why 13(V/KIc) with deuteriated isocitrate decreases more than predicted. The pK seen in the 13(V/KIc) pH profile for isocitrate is 4.5. This pK is displaced 1.2 pH units from the true pK of the acid/base functionality of 5.7 seen in the pKi profile for oxalylglycine, a competitive inhibitor for isocitrate. From this displacement, catalysis is estimated to be 16 times faster than substrate dissociation. By use of the pH-dependent partitioning ratio of the reaction intermediate oxalosuccinate between decarboxylation to 2-ketoglutarate and reduction to isocitrate, the forward commitment to catalysis for decarboxylation was determined to be 7.3 at pH 5.4 and 3.2 at pH 5.0. This gives an intrinsic 13C isotope effect for decarboxylation of 1.050. 3-Fluoroisocitrate is a new substrate oxidatively decarboxylated by NADP isocitrate dehydrogenase. At neutral pH, D(V/K3-F-Ic) = 1.45 and 13(V/K3-F-Ic) = 1.0129. At pH 5.2, 13(V/K3-F-Ic) increases to 1.0186, indicating that a finite, but diminished, external commitment remains at neutral pH. The product of oxidative decarboxylation of 3-hydroxyisocitrate by NADP isocitrate dehydrogenase is 2-hydroxy-3-ketoglutarate. This results from enzymatic protonation of the cis-enediol intermediate at C2 rather than C3 (as seen with isocitrate and 3-fluoroisocitrate). 2-Hydroxy-3-ketoglutarate further decarboxylates in solution to 2-hydroxy-3-ketobutyrate, which further decarboxylates to acetol. This makes 3-hydroxyisocitrate unsuitable for 13C isotope effect studies.

Animals↗
PubMed2004

Fractionation of stable isotope-labeled organic pollutants as a potential tracer of atmospheric transport processes.

To test the potential for using stable isotope fractionation to examine the atmospheric transport of semivolatile organic compounds (SOCs), we conducted simplified distillation experiments in the laboratory and a tracer-release experiment using mixtures of stable isotope-labeled (D and 13C) and unlabeled SOCs. Perdeuterated phenanthrene and alpha-hexachlorocyclohexane were transported more slowly via air-water gas exchange in our laboratory experiments, resulting in significant isotope fractionation of perdeuterated/unlabeled compound mixtures. In contrast, isotope fractionation of 13C6-labeled SOCs was much lower. A field tracer-release study was then conducted by spiking a seawater retention pond with a mixture of D10-labeled, 13C2-labeled, and unlabeled phenanthrene and examining isotope fractionation of the mixture after air-water gas exchange. No preferential fractionation of D10-vs 13C2-labeled phenanthrene was observed in the pond water; however, greater fractionation of D10-vs 13C2-labeled phenanthrene was observed in air samples collected within a 1-100 m radius of the pond. Thus, stable isotope tracers may provide a means of examining the atmospheric transport and air-earth exchange rates of POPs in an environmental realistic setting.

Air Movements↗
PubMed2003

Heavy atom isotope effects on the reaction catalyzed by the oxalate decarboxylase from Bacillus subtilis.

Oxalate decarboxylase (OxDC) catalyzes a remarkable transformation in which the C-C bond in oxalate is cleaved to give carbon dioxide and formate. Like the native OxDC isolated from Aspergillus niger, the recombinant, bacterial OxDC from Bacillus subtilis contains Mn(II) in its resting state and requires catalytic dioxygen for activity. The most likely mechanism for OxDC-catalyzed C-C bond cleavage involves the participation of free radical intermediates, although this hypothesis remains to be unequivocally demonstrated. Efforts to delineate the catalytic mechanism have been placed on a firm foundation by the high-resolution crystal structure of recombinant, wild type B. subtilis OxDC (Anand et al., Biochemistry 2002, 41, 7659-7669). We now report the results of heavy-atom kinetic isotope effect measurements for the OxDC-catalyzed decarboxylation of oxalate, in what appear to be the first detailed studies of the mechanism employed by OxDC. At pH 4.2, the OxDC-catalyzed formation of formate and CO(2) have normal (13)C isotope effects of 1.5% +/- 0.1% and 0.5% +/- 0.1%, respectively, while the (18)O isotope effect on the formation of formate is 1.1% +/- 0.2% normal. Similarly at pH 5.7, the production of formate and CO(2) exhibits normal (13)C isotope effects of 1.9% +/- 0.1% and 0.8% +/- 0.1%, respectively, and the (18)O isotope effect on the formation of formate is 1.0% +/- 0.2% normal. The (18)O isotope effect on the formation of CO(2), however, 0.7% +/- 0.2%, is inverse at pH 5.7. These results are consistent with a multistep model in which a reversible, proton-coupled, electron transfer from bound oxalate to the Mn-enzyme gives an oxalate radical, which decarboxylates to yield a formate radical anion. Subsequent reduction and protonation of this intermediate then gives formate.

Bacillus subtilis↗
PubMedDate not supplied

Minimizing resolution of isotopically coded peptides in comparative proteomics.

Stable isotopes are now widely used to quantify concentration changes in proteomics. This paper focuses on the resolution of isotopically coded peptides and how isotope effects occurring during chromatographic separations can be minimized. Heavy isotope derivatizing agents used in this work were the commercially available 2H8-ICAT reagent and 13C4-succinic anhydride. The ICAT reagent derivatizes cysteine-containing peptides, whereas the succinic anhydride reacts with primary amine groups in peptides. It was observed during reversed-phase chromatography of peptides from a BSA tryptic digest differentially labeled with the 2Hr and 2H8-ICAT reagents that resolution of the isoforms exceeded 0.5 with 20% of the peptides in the digest. Three-fourths of the peptides in this group contained two cysteine residues and were doubly labeled. Only 23% of the peptides labeled with a single ICAT residue had a resolution greater than 0.4. The resolution of peptides differentially labeled with 13C- and 12C-succinate never exceeded +/- 0.01, even in the case of peptides from the BSA digest labeled with 2 mol of succinate. Because this value is within the limits of the method used to determine resolution, it was concluded the 13C- and 12C-coded isoforms of labeled peptides did not resolve. The isotope ratio in the case of 13C/12C coding could be determined from a single mass spectrum taken at any point in the elution profile. This enabled isotope ratio analysis to be completed early in the elution of a peptide from chromatography columns.

Carbon Isotopes↗
PubMed2006

Stable isotopes in elephant hair document migration patterns and diet changes.

We use chronologies of stable isotopes measured from elephant (Loxodonta africana) hair to determine migration patterns and seasonal diet changes in elephants in and near Samburu National Reserve in northern Kenya. Stable carbon isotopes record diet changes, principally enabling differentiation between browse and tropical grasses, which use the C3 and C4 photosynthetic pathways, respectively; stable nitrogen isotopes record regional patterns related to aridity, offering insight into localized ranging behavior. Isotopically identified range shifts were corroborated by global positioning system radio tracking data of the studied individuals. Comparison of the stable isotope record in the hair of one migrant individual with that of a resident population shows important differences in feeding and ranging behavior over time. Our analysis indicates that differences are the result of excursions into mesic environments coupled with intermittent crop raiding by the migrant individual. Variation in diet, quantified by using stable isotopes, can offer insight into diet-related wildlife behavior.

Animal Migration↗
PubMed2002

Sulfur and oxygen isotope geochemistry of acid mine drainage--the polymetallic sulfide deposit "himmelfahrt fundgrube" in Freiberg (Germany).

We investigated physical, chemical and isotope (S, O) parameters of sulfate from acid mine drainage from the polymetallic sulfide ore deposit Freiberg (Gennany), which was mined for more than eight hundred years. Two main groups of water were distinguished: 1. Flowing mine water with sulfate concentrations of less than 9,000 mg/l and pH values higher than 3.2, 2. Pore water in weathered low grade ores and pools with sulfate concentrations higher than 9000mg/l and pH values below 3.2. The sulfur and oxygen isotope composition of sulfate from flowing mine waters reflects mixing of sulfate from two sulfur sources: a) atmospheric sulfur from precipitation and b) sulfate formed as a result of sulfide oxidation processes. Sulfur isotope values of mine water sulfate were used to estimate the contribution of sulfate derived through oxidation of sulfides. The sulfur isotope composition of pore water sulfate and precipitated sulfate (jarosite) from weathered low grade ore samples is identical to the sulfur isotope composition of primary sulfides. The oxygen isotope composition of pore water sulfate from low grade ore samples indicates that the oxidation process proceeds relatively slowly in 02-depleted waters, probably without significant microbial catalysis.

Geological Phenomena↗