How to Convert Biological Carbon Into Graphite for AMS

Getachew, G.; Kim, Seung Hyun; Burri, Betty J.; Kelly, Peter B.; Haack, Kurt; Ognibene, Ted; Buchholz, Bruce A.; Vogel, John S.; Modrow, Jonathan; Clifford, Andrew J.

doi:10.1017/s0033822200038789

Cited by 29 publications

(77 citation statements)

References 15 publications

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“…Under these conditions, reduction time was not a significant factor and the previous method(15) needed 6 h (abscissa broken rectangle). But we confirmed that 3 h was optimal (abscissa solid rectangle) based on the uniformity of the graphite coat when CO 2 was reduced at 500 °C (data not shown).…”

Section: Resultsmentioning

confidence: 93%

Biological/Biomedical Accelerator Mass Spectrometry Targets. 1. Optimizing the CO₂ Reduction Step Using Zinc Dust

2008

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Biological and biomedical applications of accelerator mass spectrometry (AMS) use isotope ratio mass spectrometry to quantify minute amounts of long-lived radioisotopes such as 14C. AMS target preparation involves first the oxidation of carbon (in sample of interest) to CO2 and second the reduction of CO2 to filamentous, fluffy, fuzzy, or firm graphite-like substances that coat a −400-mesh spherical iron powder (−400MSIP) catalyst. Until now, the quality of AMS targets has been variable; consequently, they often failed to produce robust ion currents that are required for reliable, accurate, precise, and high-throughput AMS for biological/biomedical applications. Therefore, we described our optimized method for reduction of CO2 to high-quality uniform AMS targets whose morphology we visualized using scanning electron microscope pictures. Key features of our optimized method were to reduce CO2 (from a sample of interest that provided 1 mg of C) using 100 ± 1.3 mg of Zn dust, 5 ± 0.4 mg of −400MSIP, and a reduction temperature of 500 °C for 3 h. The thermodynamics of our optimized method were more favorable for production of graphite-coated iron powders (GCIP) than those of previous methods. All AMS targets from our optimized method were of 100% GCIP, the graphitization yield exceeded 90%, and δ13C was −17.9 ± 0.3‰. The GCIP reliably produced strong 12C− currents and accurate and precise Fm values. The observed Fm value for oxalic acid II NIST SRM deviated from its accepted Fm value of 1.3407 by only 0.0003 ± 0.0027 (mean ± SE, n = 32), limit of detection of 14C was 0.04 amol, and limit of quantification was 0.07 amol, and a skilled analyst can prepare as many as 270 AMS targets per day. More information on the physical (hardness/color), morphological (SEMs), and structural (FT-IR, Raman, XRD spectra) characteristics of our AMS targets that determine accurate, precise, and high-hroughput AMS measurement are in the companion paper.

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Section: Resultsmentioning

confidence: 93%

Biological/Biomedical Accelerator Mass Spectrometry Targets. 1. Optimizing the CO₂ Reduction Step Using Zinc Dust

2008

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“…(7) On the other hand our optimized CO 2 reduction method formed only GCIP (black, soft powder, uniform, fuzz) 100% of the time. (13) In general, the presence of a nongraphitic carbon or Fe 3 C crystal resulted in the formation of a harder carbon structure than a compact graphitized carbon.…”

Section: Discussionmentioning

confidence: 99%

Biological/Biomedical Accelerator Mass Spectrometry Targets. 2. Physical, Morphological, and Structural Characteristics

2008

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The number of biological/biomedical applications that require AMS to achieve their goals is increasing, and so is the need for a better understanding of the physical, morphological, and structural traits of high quality of AMS targets. The metrics of quality included color, hardness/texture, and appearance (photo and SEM), along with FT-IR, Raman, and powder X-ray diffraction spectra that correlate positively with reliable and intense ion currents and accuracy, precision, and sensitivity of fraction modern (Fm). Our previous method produced AMS targets of gray-colored iron−carbon materials (ICM) 20% of the time and of graphite-coated iron (GCI) 80% of the time. The ICM was hard, its FT-IR spectra lacked the sp2 bond, its Raman spectra had no detectable G′ band at 2700 cm−1, and it had more iron carbide (Fe3C) crystal than nanocrystalline graphite or graphitizable carbon (g-C). ICM produced low and variable ion current whereas the opposite was true for the graphitic GCI. Our optimized method produced AMS targets of graphite-coated iron powder (GCIP) 100% of the time. The GCIP shared some of the same properties as GCI in that both were black in color, both produced robust ion current consistently, their FT-IR spectra had the sp2 bond, their Raman spectra had matching D, G, G′, D+G, and D′′ bands, and their XRD spectra showed matching crystal size. GCIP was a powder that was easy to tamp into AMS target holders that also facilitated high throughput. We concluded that AMS targets of GCIP were a mix of graphitizable carbon and Fe3C crystal, because none of their spectra, FT-IR, Raman, or XRD, matched exactly those of the graphite standard. Nevertheless, AMS targets of GCIP consistently produced the strong, reliable, and reproducible ion currents for high-throughput AMS analysis (270 targets per skilled analyst/day) along with accurate and precise Fm values.

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“…HPLC fractions were collected, dried and converted to graphite as previously described (Buchholz et al, [2000]; Getachew et al, [2006]; Miyashita et al, [2001]). 14 C contents in the graphite samples were quantified by AMS (Ognibene et al, [2002]).…”

Section: Methodsmentioning

confidence: 99%

Quantitation of NAD⁺ biosynthesis from the salvage pathway in Saccharomyces cerevisiae

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Lin

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et al. 2009

Yeast

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Nicotinamide adenine dinucleotide (NAD+) is synthesized via two major pathways in prokaryotic and eukaryotic systems: the de novo biosynthesis pathway from tryptophan precursors, or by the salvage biosynthesis pathway from either extracellular nicotinic acid or various intracellular NAD+ decomposition products. NAD+ biosynthesis via the salvage pathway has been linked to an increase in yeast replicative lifespan under calorie restriction (CR). However, the relative contribution of each pathway to NAD+ biosynthesis under both normal and CR conditions is not known. Here, we have performed lifespan, NAD+ and NADH (the reduced form of NAD+) analyses on BY4742 wild type, NAD+ salvage pathway knockout (npt1Δ), and NAD+ de novo pathway knockout (qpt1Δ) yeast strains cultured in media containing either 2% glucose (normal growth) or 0.5 % glucose (CR). We have utilized 14C labeled nicotinic acid in the culture media combined with HPLC speciation and both UV and 14C detection to quantitate the total amounts of NAD+ and NADH and the amounts derived from the salvage pathway. We observe that wild type and qpt1Δ yeast exclusively utilize extracellular nicotinic acid for NAD+ and NADH biosynthesis under both the 2% and 0.5% glucose growth conditions suggesting that the de novo pathway plays little role if a functional salvage pathway is present. We also observe that NAD+ concentrations decrease in all three strains under CR. However, unlike the wild type strain, NADH concentrations do not decrease and NAD+:NADH ratios do not increase under CR for either knockout strain. Lifespan analyses reveal that CR results in a lifespan increase of approximately 25% for the wild type and qpt1Δ strains, while no increase in lifespan is observed for the npt1Δ strain. In combination these data suggest that having a functional salvage pathway is more important than the absolute levels of NAD+ or NADH for lifespan extension under CR.

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How to Convert Biological Carbon Into Graphite for AMS

Cited by 29 publications

References 15 publications

Biological/Biomedical Accelerator Mass Spectrometry Targets. 1. Optimizing the CO₂ Reduction Step Using Zinc Dust

Biological/Biomedical Accelerator Mass Spectrometry Targets. 1. Optimizing the CO₂ Reduction Step Using Zinc Dust

Biological/Biomedical Accelerator Mass Spectrometry Targets. 2. Physical, Morphological, and Structural Characteristics

Quantitation of NAD⁺ biosynthesis from the salvage pathway in Saccharomyces cerevisiae

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How to Convert Biological Carbon Into Graphite for AMS

Cited by 29 publications

References 15 publications

Biological/Biomedical Accelerator Mass Spectrometry Targets. 1. Optimizing the CO2 Reduction Step Using Zinc Dust

Biological/Biomedical Accelerator Mass Spectrometry Targets. 1. Optimizing the CO2 Reduction Step Using Zinc Dust

Biological/Biomedical Accelerator Mass Spectrometry Targets. 2. Physical, Morphological, and Structural Characteristics

Quantitation of NAD+ biosynthesis from the salvage pathway in Saccharomyces cerevisiae

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Product

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Biological/Biomedical Accelerator Mass Spectrometry Targets. 1. Optimizing the CO₂ Reduction Step Using Zinc Dust

Biological/Biomedical Accelerator Mass Spectrometry Targets. 1. Optimizing the CO₂ Reduction Step Using Zinc Dust

Quantitation of NAD⁺ biosynthesis from the salvage pathway in Saccharomyces cerevisiae