Dietary vitamin E reaches the mitochondria in the flight muscle of zebra finches but only if they exercise.

Whether dietary antioxidants are effective for alleviating oxidative costs associated with energy-demanding life events first requires they are successfully absorbed in the digestive tract and transported to sites associated with reactive species production (e.g. the mitochondria). Flying birds are under high energy and oxidative demands, and although birds commonly ingest dietary antioxidants in the wild, the bioavailability of these consumed antioxidants is poorly understood. We show for the first time that an ingested lipophilic antioxidant, α-tocopherol, reached the mitochondria in the flight muscles of a songbird but only if they regularly exercise (60 min of perch-to-perch flights two times in a day or 8.5 km day-1). Deuterated α-tocopherol was found in the blood of exercise-trained zebra finches within 6.5 hrs and in isolated mitochondria from pectoral muscle within 22.5 hrs, but never reached the mitochondria in caged sedentary control birds. This rapid pace (within a day) and extent of metabolic routing of a dietary antioxidant to muscle mitochondria means that daily consumption of such dietary sources can help to pay the inevitable oxidative costs of flight muscle metabolism, but only when combined with regular exercise.

Applying the principles of isotope analysis in plant and animal ecology to forensic science in the Americas.

The heart of forensic science is application of the scientific method and analytical approaches to answer questions central to solving a crime: Who, What, When, Where, and How. Forensic practitioners use fundamentals of chemistry and physics to examine evidence and infer its origin. In this regard, ecological researchers have had a significant impact on forensic science through the development and application of a specialized measurement technique-isotope analysis-for examining evidence. Here, we review the utility of isotope analysis in forensic settings from an ecological perspective, concentrating on work from the Americas completed within the last three decades. Our primary focus is on combining plant and animal physiological models with isotope analyses for source inference. Examples of the forensic application of isotopes-including stable isotopes, radiogenic isotopes, and radioisotopes-span from cotton used in counterfeit bills to anthrax shipped through the U.S. Postal Service and from beer adulterated with cheap adjuncts to human remains discovered in shallow graves. Recent methodological developments and the generation of isotope landscapes, or isoscapes, for data interpretation promise that isotope analysis will be a useful tool in ecological and forensic studies for decades to come.

Self-Assembly Directed Organization of Nanodiamond During Ionic Liquid Crystalline Polymer Formation.

The UV-initiated free radical polymerization of a lyotropic mesophase prepared by co-assembly of an aqueous mixture of an ionic liquid (IL) monomer, 3-decyl-1-vinylimidazolium chloride, in a dimethyl sulfoxide dispersion of an IL-monomer nanodiamond conjugate yields a well-ordered 2D hexagonally structured network-polymer composite. The IL monomer is covalently bound to carboxylated detonation diamond via ester-linked 3-decyl-1-vinylimidazolium bromide. Successful preparation of the amphiphile-functionalized nanodiamond is determined by ATR/FT-IR, thermogravimetric analysis, and small-angle X-ray scattering (SAXS). Mesophase and composite structure are evaluated by SAXS, revealing a columnar architecture composed of amphiphilic ionic liquid cylinders containing solvent-rich cores. Self-assembly directed site localization of the nanodiamond positions the particles in the alkyl chain continuum upon polymerization. The composite reversibly swells in ethanol allowing structural variation and modulation of the nanoparticle internal packing arrangement. This work demonstrates that through careful molecular design, self-organization and site-directed assembly of nanodiamond into chemically distinct regions of a nanostructured organogel can be achieved.

Detection of metabolic fluxes of O and H atoms into intracellular water in mammalian cells.

Metabolic processes result in the release and exchange of H and O atoms from organic material as well as some inorganic salts and gases. These fluxes of H and O atoms into intracellular water result in an isotopic gradient that can be measured experimentally. Using isotope ratio mass spectroscopy, we revealed that slightly over 50% of the H and O atoms in the intracellular water of exponentially-growing cultured Rat-1 fibroblasts were isotopically distinct from growth medium water. We then employed infrared spectromicroscopy to detect in real time the flux of H atoms in these same cells. Importantly, both of these techniques indicate that the H and O fluxes are dependent on metabolic processes; cells that are in lag phase or are quiescent exhibit a much smaller flux. In addition, water extracted from the muscle tissue of rats contained a population of H and O atoms that were isotopically distinct from body water, consistent with the results obtained using the cultured Rat-1 fibroblasts. Together these data demonstrate that metabolic processes produce fluxes of H and O atoms into intracellular water, and that these fluxes can be detected and measured in both cultured mammalian cells and in mammalian tissue.

δ2H and δ18O of human body water: a GIS model to distinguish residents from non-residents in the contiguous USA.

An understanding of the factors influencing the isotopic composition of body water is important to determine the isotopic composition of tissues that are used to reconstruct movement patterns of humans. The δ(2)H and δ(18)O values of body water (δ(2)H(bw) and δ(18)O(bw)) are related to the δ(2)H and δ(18)O values of drinking water (δ(2)H(dw) and δ(18)O(dw)), but clearly distinct because of other factors including the composition of food. Here, we develop a mechanistic geographical information system (GIS) model to produce spatial projections of δ(2)H(bw) and δ(18)O(bw) values for the USA. We investigate the influence of gender, food, and drinking water on the predicted values by comparing them with the published values. The strongest influence on the predicted values was related to the source of δ(2)H(dw) and δ(18)O(dw) values. We combine the model with equations that describe the rate of turnover to produce estimates for the time required for a non-resident to reach an isotopic equilibrium with a resident population.

Hydrogen and oxygen isotope values in hydrogen peroxide.

Hydrogen peroxide (H(2)O(2)) is a widely used oxidizer with many commercial applications; unfortunately, it also has terrorist-related uses. We analyzed 97 hydrogen peroxide solutions representing four grades purchased across the United States and in Mexico. As expected, the range of hydrogen (δ(2)H, 230‰) and oxygen (δ(18)O, 24‰) isotope values of the H(2)O(2) solutions was large, reflecting the broad isotopic range of dilution waters. This resulted in predictable linear relationships of δ(2)H and δ(18)O values of H(2)O(2) solutions that were near parallel to the Meteoric Water Line (MWL), offset by the concentration of H(2)O(2) in the solution. By grade, dilute (3 to 35%) H(2)O(2) solutions were not statistically different in slope. Although the δ(2)H values of manufactured H(2)O(2) could be different from those of water, rapid H(2)O(2)-H(2)O exchange of H atoms eliminated any distinct isotope signal. We developed a method to measure the δ(18)O value of H(2)O(2) independent of dilution water by directly measuring O(2) gas generated from a catalase-induced disproportionation reaction. We predicted that the δ(18)O values of H(2)O(2) would be similar to that of atmospheric oxygen (+23.5‰), the predominant source of oxygen in the most common H(2)O(2) manufacturing process (median disproportionated δ(18)O=23.8‰). The predictable H-O relationships in H(2)O(2) solutions make it possible to distinguish commercial dilutions from clandestine concentration practices. Future applications of this work include synthesis studies that investigate the chemical link between H(2)O(2) reagents and peroxide-based explosive products, which may assist law enforcement in criminal investigations.

Evaluating uncertainty in the calculation of non-exchangeable hydrogen fractions within organic materials.

We calculated the fraction of exchangeable hydrogen atoms in proteinaceous materials commonly analyzed for stable isotopic composition related to the region-of-origin of an animal. These included several types of alpha- and beta-keratin, and muscle tissue. We find that the fraction of H atoms in keratin available for exchange at a biologically relevant temperature (25 degrees C) averaged 9% across a range of ground organic materials, but was as high as approximately 17% in cut hair; muscle tissue has approximately 12% exchangeable H atoms. Under most analysis conditions, the difference in exchangeable fractions due to physical sample processing has a minimal effect on the calculated delta2H values of the non-exchangeable H atoms within a keratin-containing tissue (<2 per thousand). However, extreme mismatches between sample and reference material types could affect delta2H values.

Dietary and physiological controls on the hydrogen and oxygen isotope ratios of hair from mid-20th century indigenous populations.

A semimechanistic model has recently been proposed to explain observed correlations between the H and O isotopic composition of hair from modern residents of the USA and the isotopic composition of drinking water, but the applicability of this model to hair from non-USA and preglobalization populations is unknown. Here we test the model against data from hair samples collected during the 1930s-1950s from populations of five continents. Although C and N isotopes confirm that the samples represent a much larger range of dietary "space" than the modern USA residents, the model is able to reproduce the observed delta(2)H and delta(18)O values given reasonable adjustments to 2 model parameters: the fraction of dietary intake derived from locally produced foods and the fraction of keratin H fixed during the in vivo synthesis of amino acids. The model is most sensitive to the local dietary intake, which appears to constitute between 60% and 80% of diet among the groups sampled. The isotopic data are consistent with a trophic-level effect on protein H isotopes, which we suggest primarily reflects mixing of (2)H-enriched water and (2)H-depleted food H in the body rather than fractionation during biosynthesis. Samples from Inuit groups suggest that humans with marine-dominated diets can be identified on the basis of coupled delta(2)H and delta(18)O values of hair. These results indicate a dual role for H and O isotopic measurements of keratin, including both biological (diet, physiology) and environmental (geographic movement, paleoclimate) reconstruction.

Variation of hydrogen, carbon, nitrogen, and oxygen stable isotope ratios in an American diet: fast food meals.

The stable isotopes of hydrogen, carbon, nitrogen, and oxygen provide insights into a heterotrophic organism's diet and geographic origin. Although the contribution of food delta (2)H and delta (18)O to the final tissue signal will not vary for constrained diets, it will for animals eating varied diets, that is, humans. This study surveyed the isotopic range in one portion of the American diet, fast food meals. Hamburger patties, buns, and French fries from national chain restaurants across the United States and from local restaurants (Salt Lake City, UT, and Charleston, SC) were analyzed for delta (2)H, delta (13)C, delta (15)N (patties only) and delta (18)O values. Patties and buns from local Utah restaurants were more depleted for delta (2)H, delta (13)C, and delta (18)O values than samples from other restaurants. There were no significant differences in delta values among French fries. All three components of the fast food meal displayed significant linear delta (2)H versus delta (18)O relationships (delta (2)H = 7.8delta (18)O - 237 per thousand, delta (2)H = 5.9delta (18)O - 258 per thousand, and delta (2)H = 3.3delta (18)O - 231 per thousand for patties, buns, and fries, respectively). The findings show that significant predictable variation exists in the stable isotopic composition of fast food meals. It is proposed that the variation in delta (13)C values of hamburger (beef) patties is indicative of differences in cattle-rearing practices, whereas delta (2)H and delta (18)O values are evidence of geographic variation in food sources. Although the patterns support the concept of a "continental" supermarket diet, there appears to be a strong regional component within the diet.

Hydrogen and oxygen isotope ratios in human hair are related to geography.

We develop and test a model to predict the geographic region-of-origin of humans based on the stable isotope composition of their scalp hair. This model incorporates exchangeable and nonexchangeable hydrogen and oxygen atoms in amino acids to predict the delta(2)H and delta(18)O values of scalp hair (primarily keratin). We evaluated model predictions with stable isotope analyses of human hair from 65 cities across the United States. The model, which predicts hair isotopic composition as a function of drinking water, bulk diet, and dietary protein isotope ratios, explains >85% of the observed variation and reproduces the observed slopes relating the isotopic composition of hair samples to that of local drinking water. Based on the geographical distributions of the isotope ratios of tap waters and the assumption of a "continental supermarket" dietary input, we constructed maps of the expected average H and O isotope ratios in human hair across the contiguous 48 states. Applications of this model and these observations are extensive and include detection of dietary information, reconstruction of historic movements of individuals, and provision of region-of-origin information for unidentified human remains.

Determining biological tissue turnover using stable isotopes: the reaction progress variable.

The reaction progress variable is applied to stable isotope turnover of biological tissues. This approach has the advantage of readily determining whether more than one isotope turnover pool is present; in addition, the normalization process inherent to the model means that multiple experiments can be considered together although the initial and final isotope compositions are different. Consideration of multiple isotope turnover pools allows calculation of diet histories of animals using a time sequence of isotope measurements along with isotope turnover pools. The delayed release of blood cells from bone marrow during a diet turnover experiment can be quantified using this approach. Turnover pools can also be corrected for increasing mass during an experiment, such as when the animals are actively growing. Previous growth models have been for exponential growth; the approach here can be used for several different growth models.

Metabolic routing of dietary nutrients in birds: effects of diet quality and macronutrient composition revealed using stable isotopes.

During fall migration many songbirds switch from consuming primarily insects to consuming mostly fruit. Fruits with more carbohydrates and less protein may be sufficient to rebuild expended fat stores, but such fruits may be inadequate to replace catabolized protein. We manipulated the concentrations and isotopic signatures of macronutrients in diets fed to birds to study the effects of diet quality on metabolic routing of dietary nutrients. We estimated that approximately 45% and 75%, respectively, of the carbon in proteinaceous tissue of birds switched to high- or low-protein diets came from nonprotein dietary sources. In contrast, we estimated that approximately 100% and 20%-80%, respectively, of the nitrogen in proteinaceous tissues of birds switched to high- or low-protein diets was attributable to dietary protein. Thus, the routing and assimilation of dietary carbon and nitrogen differed depending on diet composition. As a result, delta (15)N of tissues collected from wild animals that consume high-quality diets may reliably indicate the dietary protein source, whereas delta (13)C of these same tissues is likely the product of metabolic routing of carbon from several macronutrients. These results have implications for how isotopic discrimination is best estimated and how we can study macronutrient routing in wild animals.

Stable isotopes in breath, blood, feces and feathers can indicate intra-individual changes in the diet of migratory songbirds.

We used stable isotopes of C in breath, blood, feces and feathers to identify intra-individual changes in diet and the timescale of diet changes in free-living songbirds at a stopover site. Because accurate interpretation of differences between the delta13C of breath, plasma, and red blood cells (RBCs) relative to diet requires knowing the turnover rate of C within them, we determined the rate of change of C in breath, plasma and RBCs for yellow-rumped warblers (Dendroica coronata). Half-lives of C in breath, plasma, and RBCs were 4.4+/-2.1 h, 24.8+/-12.3 h and 10.9+/-3.2 days, respectively, for yellow-rumped warblers. delta13C of breath, plasma, RBCs and feces from wild-caught golden-crowned kinglets (Regulus satrapa), ruby-crowned kinglets (R. calendula) and gray catbirds (Dumetella carolinensis) indicated that they had maintained an isotopically consistent diet for an extended period of time. However, delta13C of breath and plasma indicated that white-throated sparrows (Zonotrichia albicollis) had recently expanded their diet to include a C4 dietary component. Likewise, delta13C of breath, plasma, RBCs and feces indicated that some wild-caught yellow-rumped warblers had consumed foods with a more enriched protein signature prior to their arrival on Block Island, and since arrival, they had consumed mostly northern bayberry (Myrica pensylvanica). Therefore, comparisons of the delta13C of breath, plasma, RBCs, feces and feathers from individual songbirds can indicate changes in diet and provide an estimate of the timescale of the diet change.