Isotope

Source: www.msnbc.msn.com --- 13 days ago
Nearly a year after the discovery of a radioactive Isotope in some wells around Fallon prompted two dairies to dump milk, federal officials announced Thursday plans to conduct a study to determine the extent of the problem. ...

Source: www.msnbc.msn.com --- 48 days ago
The U.S. Department of Energy is chipping in $100,000 to help companies that want to use the Idaho National Laboratory's Advanced Test Reactor to create radioactive isotopes for research and cancer treatments. ...

Source: www.ncbi.nlm.nih.gov --- 24 days ago
Multiple segmental and selective Isotope labeling of large RNA for NMR structural studies. Nucleic Acids Res. 2008 Jun 26; Authors: Nelissen FH, van Gammeren AJ, Tessari M, Girard FC, Heus HA, Wijmenga SS Multiple segmental and selective Isotope labeling of RNA with three segments has been demonstrated by introducing an RNA segment, selectively labeled with (13)C(9)/(15)N(2)/(2)H((1', 3', 4', 5', 5''))-labeled uridine residues, into the central position of the 20 kDa epsilon-RNA of Duck Hepatitis B Virus. The RNA molecules were produced via two efficient protocols: a two-step protocol, which uses T4 DNA ligase and T4 RNA ligase 1, and a one-pot protocol, which uses T4 RNA ligase 1 alone. With T4 RNA ligase 1 all not-to-be-ligated termini are usually protected to prevent formation of side products. We show that such labor-intensive protection of termini is not required, provided segmentation sites can be chosen such that the segments fold into the target structure or target-like structures and thus are not trapped into stable alternate structures. These sites can be reliably predicted via DINAMelt. The simplified NMR spectrum provided evidence for the presence of a U28 H(3)-imino resonance, previously obscured in the fully labeled sample, and thus of the non-canonical base pair U28:C37. The demonstrated multiple segmental labeling protocols are generally applicable to large RNA molecules and can be extended to more than three segments. ...

Source: www.ncbi.nlm.nih.gov --- 14 days ago
Related Articles Influence of dietary composition on the carbon, nitrogen, oxygen and hydrogen stable Isotope ratios of milk. Rapid Commun Mass Spectrom. 2008 Jun;22(11):1690-6 Authors: Camin F, Perini M, Colombari G, Bontempo L, Versini G The stable Isotope ratios ((13)C/(12)C, (15)N/(14)N, (18)O/(16)O, D/H) of animal feed and milk were investigated, considering cows stabled in two farms and fed with diets made up of different kinds of C(3) plants and different amounts of maize. Maize was characterised by delta(13)C, delta(18)O and deltaD values significantly higher than those of the C(3) plants, while, for the C(3) plants, Festuca arudinacea had significantly higher content of (13)C and (15)N. The delta(13)C and delta(18)O values of the overall diet and the delta(13)C of milk casein and lipids were shown to be significantly correlated with the percentage of maize in the animal diet. On the other hand, the delta(18)O values of milk water and the delta(18)O, deltaD and delta(15)N values of casein were shown to be only slightly influenced by the amount of maize in the feed, being probably more closely correlated with the geo-climatic and pedological characteristics of the area of origin and with the presence of fresh plant or silage in the ration. The delta(13)C value of casein was shown to be a suitable parameter for evaluating the amount of maize in the diet: each 10% increase in the maize content corresponded to a shift of 0.7 per th ...

Source: www.moreover.com --- 4 days ago
Extract not available. ...

Source: www.ncbi.nlm.nih.gov --- 13 days ago
Related Articles Combined carbon and hydrogen Isotope fractionation investigations for elucidating benzene biodegradation pathways. Environ Sci Technol. 2008 Jun 15;42(12):4356-63 Authors: Fischer A, Herklotz I, Herrmann S, Thullner M, Weelink SA, Stams AJ, Schlömann M, Richnow HH, Vogt C Recently, combined carbon and hydrogen Isotope fractionation investigations have emerged as a powerful tool for the characterization of reaction mechanisms relevant for the removal of organic pollutants. Here, we applied this approach in order to differentiate benzene biodegradation pathways under oxic and anoxic conditions in laboratory experiments. Carbon and hydrogen Isotope fractionation of benzene was studied with four different aerobic strains using a monooxygenase or a dioxygenase for the initial benzene attack, a facultative anaerobic chlorate-reducing strain as well as a sulfate-reducing mixed culture. Carbon and hydrogen enrichment factors (epsilon(C), epsilon(H)) varied for the specific pathways and degradation conditions, respectively, so that from the individual enrichment factors only limited information could be obtained for the identification of benzene biodegradation pathways. However, using the slope derived from hydrogen vs carbon Isotope discriminations or the ratio of hydrogen to carbon enrichment factors (lambda = deltaH/ deltaC approximately epsilon(H)/epsilon(C)), benzene degradation mechanisms could be distinguished. Although ...

Source: www.ncbi.nlm.nih.gov --- 6 days ago
Related Articles Isotope sensitive branching and kinetic Isotope effects in the reaction of deuterated arachidonic acids with human 12- and 15-lipoxygenases. Biochemistry. 2008 Jul 8;47(27):7295-303 Authors: Jacquot C, Wecksler AT, McGinley CM, Segraves EN, Holman TR, van der Donk WA Lipoxygenases (LOs) catalyze lipid peroxidation and have been implicated in a number of human diseases connected to oxidative stress and inflammation. These enzymes have also attracted considerable attention due to large kinetic Isotope effects (30-80) for the rate-limiting hydrogen abstraction step with linoleic acid (LA) as substrate. Herein, we report kinetic Isotope effects (KIEs) in the reactions of three human LOs (platelet 12-hLO, reticulocyte 15-hLO-1, and epithelial 15-hLO-2) with arachidonic acid (AA). Surprisingly, the observed KIEs with AA were much smaller than the previously reported values with LA. Investigation into the origins for the smaller KIEs led to the discovery of Isotope sensitive branching of the reaction pathways. Product distribution analysis demonstrated an inversion in the regioselectivity of 15-hLO-1, with hydrogen abstraction from C13 being the major pathway with unlabeled AA but abstraction from C10 predominating when the methylene group at position 13 was deuterated. Smaller but clear changes in regioselectivity were also observed for 12-hLO and 15-hLO-2. PMID: 18547056 [PubMed - indexed for MEDLINE] ...

Source: www.ncbi.nlm.nih.gov --- 41 days ago
Related Articles An innovative molybdenum column liner for oxygen and hydrogen stable Isotope analysis by pyrolysis. Rapid Commun Mass Spectrom. 2008 Apr;22(8):1117-26 Authors: Stuart-Williams H, Wong SC, Farquhar GD, Keitel C, Clayton S The most widely used method for pyrolysing samples for hydrogen or oxygen isotopic analysis involves heating them to greater than 1300 degrees C in a helium stream passed through a glassy carbon tube in an alumina casing. There are a number of difficulties with this. Glassy carbon tubes are expensive and interaction between the carbon tube and the outer casing produces unwanted carbon monoxide by reduction of the alumina at high temperatures. The latter effect is overwhelming if temperatures of 1400 degrees C or greater are used for pyrolysis. We experimented with lining alumina casings with pure molybdenum sheet. It is relatively cheap, conforms well to the interior of the reactor tube (to avoid carrier and sample bypassing of the carbon pack), resists high temperatures and neither oxidises excessively nor absorbs the gases. The main disadvantages are that silver sample cups must be used and that the molybdenum degrades over time by formation of the carbide. We can maintain sharp peaks, high precision and good accuracy over more than 700 solid samples for both hydrogen and oxygen. The reactors last longer for water injections. The molybdenum in the columns does not contribute greatly to memory effect ...

Source: www.ncbi.nlm.nih.gov --- 43 days ago
Related Articles Isotope-coded, iodoacetamide-based reagent to determine individual cysteine pK(a) values by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Anal Biochem. 2008 Apr 15;375(2):187-95 Authors: Nelson KJ, Day AE, Zeng BB, King SB, Poole LB Cysteine reactivity in enzymes is imparted to a large extent by the stabilization of the deprotonated form of the reduced cysteine (i.e., the thiolate) within the active site. Although this is likely to be an important chemical attribute of many thiol-based enzymes, including cysteine-dependent peroxidases (peroxiredoxins) and proteases, only relatively few pK(a) values have been determined experimentally. Presented here is a new technique for determining the pK(a) value of cysteine residues through quantitative mass spectrometry following chemical modification with an iodoacetamide-based reagent over a range of pH buffers. This Isotope-coded reagent, N-phenyl iodoacetamide (iodoacetanilide), is readily prepared in deuterated (d(5)) and protiated (d(0)) versions and is more reactive toward free cysteine than is iodoacetamide. Using this approach, the pK(a) values for the two cysteine residues in Escherichia coli thioredoxin were determined to be 6.5 and greater than 10.0, in good agreement with previous reports using chemical modification approaches. This technique allows the pK(a) of specific cysteine residues to be determined in a clear, fast, and simple m ...

Source: www.cbc.ca --- 43 days ago
MDS Nordion, the company that buys isotopes from AECL's Chalk River reactor, predicts more shortages in the future. The company's president Steve West appeared before the House of Commons Committee on Natural Resources to talk about AECL's decision to abandon construction of its two MAPLE reactors. AECL cancelled construction in May saying it was costing too much to solve the reactors' ongoing technical problems. ...

Source: www.blackwell-synergy.com --- 32 days ago
FEBS Journal, Volume 0, Issue 0, Page ???, OnlineEarly Articles. A common feature of all the proposed mechanisms for monoamine oxidase is the initiation of catalysis with the deprotonated form of the amine substrate in the enzyme–substrate complex. However, recent steady-state kinetic studies on the pH dependence of ... ...

Source: pubs.acs.org --- 11 days ago
Jongcheol Seo, Min-Soo Suh, T. Daniel Thangadurai, Jinhee Kim, Young Ho Rhee, Hye-Joo Yoon, and Seung Koo Shin Web Release Date: Sat, 12 Jul 2008 00:00:00 EDT (Accelerated Article) DOI: 10.1021/ac801007y ...

Source: pubs.acs.org --- 40 days ago
Kay Knöller, Carsten Vogt, Stefan Feisthauer, Stephan M. Weise, Holger Weiss, and Hans-Hermann Richnow Web Release Date: Sat, 14 Jun 2008 00:00:00 EDT (Article) DOI: 10.1021/es800331p ...

Source: pubs.acs.org --- 35 days ago
Laura R. McCunn, Joseph R. Roscioli, Ben M. Elliott, Mark A. Johnson, and Anne B. McCoy Web Release Date: Wed, 18 Jun 2008 00:00:00 EDT (Article) DOI: 10.1021/jp802172q ...

Source: pubs.acs.org --- 50 days ago
Daniel G. Burke and Lindsey G. Mackay Web Release Date: Tue, 3 Jun 2008 00:00:00 EDT (Article) DOI: 10.1021/ac800270u ...

Source: pubs.acs.org --- 34 days ago
Rebeca Santamaria-Fernandez, David Carter, and Ruth Hearn Web Release Date: Fri, 20 Jun 2008 00:00:00 EDT (Article) DOI: 10.1021/ac800621u ...

Source: pubs.acs.org --- 47 days ago
D. Ryan Georgianna, Adam M. Hawkridge, David C. Muddiman, and Gary A. Payne Web Release Date: Thu, 5 Jun 2008 00:00:00 EDT (Article) DOI: 10.1021/pr8001047 ...

Source: pubs.acs.org --- 43 days ago
Yun Lu, Fengrui Qu, Brian Moore, Donald Endicott, and William Kuester Web Release Date: Wed, 11 Jun 2008 00:00:00 EDT (Article) DOI: 10.1021/jo800820u ...

Source: pubs.acs.org --- 51 days ago
Zhengzheng Pan, John H. Horner, and Martin Newcomb Web Release Date: Sat, 31 May 2008 00:00:00 EDT (Communication) DOI: 10.1021/ja802484n ...

Source: pubs.acs.org --- 47 days ago
Liviu M. Mirica, Kevin P. McCusker, Jeffrey W. Munos, Hung-wen Liu, and Judith P. Klinman Web Release Date: Sat, 7 Jun 2008 00:00:00 EDT (Communication) DOI: 10.1021/ja800265s ...