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Mantha OL, Mahé M, Mahéo K, Fromont G, Guéguinou M, Tea I, Hankard R, De Luca A. Understanding natural isotopic variations in cultured cancer cells. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2024; 38:e9878. [PMID: 39117991 DOI: 10.1002/rcm.9878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 06/14/2024] [Accepted: 07/15/2024] [Indexed: 08/10/2024]
Abstract
RATIONALE Natural variations in the abundance of the stable isotopes of nitrogen (δ15N) and carbon (δ13C) offer valuable insights into metabolic fluxes. In the wake of strong interest in cancer metabolism, recent research has revealed δ15N and δ13C variations in cancerous compared to non-cancerous tissues and cell lines. However, our understanding of natural isotopic variations in cultured mammalian cells, particularly in relation to metabolism, remains limited. This study aims to start addressing this gap using metabolic modulations in cells cultured under controlled conditions. METHODS Prostate cancer cells (PC3) were cultured in different conditions and their δ15N and δ13C were measured using isotope ratio mass spectrometry. Isotopic variations during successive cell culture passages were assessed and two widely used cell culture media (RPMI and DMEM) were compared. Metabolism was modulated through glutamine deprivation and hypoxia. RESULTS Successive cell culture passages generally resulted in reproducible δ15N and δ13C values. The impact of culture medium composition on δ15N and δ13C of the cells highlights the importance of maintaining a consistent medium composition across conditions whenever possible. Glutamine deprivation and hypoxia induced a lower δ13C in bulk cell samples, with only the former affecting δ15N. Gaps between theory and experiments were bridged and the lessons learned throughout the process are provided. CONCLUSIONS Exposing cultured cancer cells to hypoxia allowed us to further investigate the relation between metabolic modulations and natural isotopic variations, while mitigating the confounding impact of changing culture medium composition. This study highlights the potential of natural δ13C variations for studying substrate fluxes and nutrient allocation in reproducible culture conditions. Considering cell yield and culture medium composition is pivotal to the success of this approach.
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Affiliation(s)
- Olivier L Mantha
- Niche, Nutrition, Cancer & Oxidative Metabolism (N2COX) UMR 1069, University of Tours, INSERM, Tours, France
| | - Marie Mahé
- Niche, Nutrition, Cancer & Oxidative Metabolism (N2COX) UMR 1069, University of Tours, INSERM, Tours, France
- Institut de Cancérologie de l'Ouest, Angers, France
| | - Karine Mahéo
- Niche, Nutrition, Cancer & Oxidative Metabolism (N2COX) UMR 1069, University of Tours, INSERM, Tours, France
| | - Gaëlle Fromont
- Niche, Nutrition, Cancer & Oxidative Metabolism (N2COX) UMR 1069, University of Tours, INSERM, Tours, France
| | - Maxime Guéguinou
- Niche, Nutrition, Cancer & Oxidative Metabolism (N2COX) UMR 1069, University of Tours, INSERM, Tours, France
| | - Illa Tea
- Nantes Université, CNRS, CEISAM, UMR6230, Nantes, France
| | - Régis Hankard
- Niche, Nutrition, Cancer & Oxidative Metabolism (N2COX) UMR 1069, University of Tours, INSERM, Tours, France
| | - Arnaud De Luca
- Niche, Nutrition, Cancer & Oxidative Metabolism (N2COX) UMR 1069, University of Tours, INSERM, Tours, France
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Hoffman DW, Rasmussen C. Position-specific carbon stable isotope analysis of glyphosate: isotope fingerprinting of molecules within a mixture. Anal Bioanal Chem 2024; 416:3847-3856. [PMID: 38740591 DOI: 10.1007/s00216-024-05326-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Revised: 04/27/2024] [Accepted: 04/30/2024] [Indexed: 05/16/2024]
Abstract
Glyphosate [N-(phosphonomethyl) glycine] is a widely used herbicide and a molecule of interest in the environmental sciences, due to its global use in agriculture and its potential impact on ecosystems. This study presents the first position-specific carbon isotope (13C/12C) analyses of glyphosates from multiple sources. In contrast to traditional isotope ratio mass spectrometry (IRMS), position-specific analysis provides 13C/12C ratios at individual carbon atom positions within a molecule, rather than an average carbon isotope ratio across a mixture or a specific compound. In this work, glyphosate in commercial herbicides was analyzed with only minimal purification, using a nuclear magnetic resonance (NMR) spectroscopy method that detects 1H nuclei with bonds to either 13C or 12C, and isolates the signals of interest from other signals in the mixture. Results demonstrate that glyphosate from different sources can have significantly different intramolecular 13C/12C distributions, which were found to be spread over a wide range, with δ13C Vienna Peedee Belemnite (VPDB) values of -28.7 to -57.9‰. In each glyphosate, the carbon with a bond to the phosphorus atom was found to be depleted in 13C compared to the carbon at the C2 position, by 4 to 10‰. Aminomethylphosphonic acid (AMPA) was analyzed for method validation; AMPA contains only a single carbon position, so the 13C/12C results provided by the NMR method could be directly compared with traditional isotope ratio mass spectrometry. The glyphosate mixtures were also analyzed by IRMS to obtain their average 13C/12C ratios, for comparison with our position-specific results. This comparison revealed that the IRMS results significantly disguise the intramolecular isotope distribution. Finally, we introduce a 31P NMR method that can provide a position-specific 13C/12C ratio for carbon positions with a C-P chemical bond, and the results obtained by 1H and 31P for C3 carbon agree with one another within their analytical uncertainty. These analytical tools for position-specific carbon isotope analysis permit the isotopic fingerprinting of target molecules within a mixture, with potential applications in a range of fields, including the environmental sciences and chemical forensics.
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Affiliation(s)
- David W Hoffman
- Department of Molecular Biosciences, The University of Texas at Austin, 100 East 24th St., Austin, TX, 78712, USA.
| | - Cornelia Rasmussen
- Institute for Geophysics, The University of Texas at Austin, J. J. Pickle Research Campus, 10601 Exploration Way, Austin, TX, 78758, USA
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Rodríguez-Jiménez JMDJ, Montalvo-González E, López-García UM, Barros-Castillo JC, Ragazzo-Sánchez JA, García-Magaña MDL. Guamara and Cocuixtle: Source of Proteases for the Transformation of Shrimp By-Products into Hydrolysates with Potential Application. BIOLOGY 2023; 12:biology12050753. [PMID: 37237565 DOI: 10.3390/biology12050753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 05/15/2023] [Accepted: 05/18/2023] [Indexed: 05/28/2023]
Abstract
Since the fruits of Bromelia pinguin and Bromelia karatas are rich in proteases, the aim of this research was to optimize the hydrolysis process of cooked white shrimp by-products due to the effect of these proteases. A robust Taguchi L16' design was used to optimize the hydrolysis process. Similarly, the amino acid profile by GC-MS and antioxidant capacity (ABTS and FRAP) were determined. The optimal conditions for hydrolysis of cooked shrimp by-products were pH 8.0, 30 °C, 0.5 h, 1 g of substrate and 100 µg/mL of B. karatas, pH 7.5, 40 °C, 0.5 h, 0.5 g substrate and 100 µg/mL enzyme extract from B. pinguin and pH 7.0, 37 °C, 1 h, 1.5 g substrate and 100 µg/mL enzyme bromelain. The optimized hydrolyzates of B. karatas B. pinguin and bromelain had 8 essential amino acids in their composition. The evaluation of the antioxidant capacity of the hydrolyzates under optimal conditions showed more than 80% inhibition of in ABTS radical, B. karatas hydrolyzates had better higher ferric ion reduction capacity with 10.09 ± 0.02 mM TE/mL. Finally, the use of proteolytic extracts from B. pinguin and B. karatas to optimize hydrolysis process allowed obtaining hydrolyzates of cooked shrimp by-products with potential antioxidant capacity.
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Affiliation(s)
- Juan Miguel de Jesús Rodríguez-Jiménez
- Laboratorio Integral de Investigación en Alimentos, Tecnológico Nacional de México/Instituto Tecnológico de Tepic. Avenida Tecnológico 2595, Fracc. Lagos del Country, Tepic 63175, Nayarit, Mexico
| | - Efigenia Montalvo-González
- Laboratorio Integral de Investigación en Alimentos, Tecnológico Nacional de México/Instituto Tecnológico de Tepic. Avenida Tecnológico 2595, Fracc. Lagos del Country, Tepic 63175, Nayarit, Mexico
| | - Ulises Miguel López-García
- Laboratorio Integral de Investigación en Alimentos, Tecnológico Nacional de México/Instituto Tecnológico de Tepic. Avenida Tecnológico 2595, Fracc. Lagos del Country, Tepic 63175, Nayarit, Mexico
| | - Julio César Barros-Castillo
- Laboratorio Integral de Investigación en Alimentos, Tecnológico Nacional de México/Instituto Tecnológico de Tepic. Avenida Tecnológico 2595, Fracc. Lagos del Country, Tepic 63175, Nayarit, Mexico
| | - Juan Arturo Ragazzo-Sánchez
- Laboratorio Integral de Investigación en Alimentos, Tecnológico Nacional de México/Instituto Tecnológico de Tepic. Avenida Tecnológico 2595, Fracc. Lagos del Country, Tepic 63175, Nayarit, Mexico
| | - María de Lourdes García-Magaña
- Laboratorio Integral de Investigación en Alimentos, Tecnológico Nacional de México/Instituto Tecnológico de Tepic. Avenida Tecnológico 2595, Fracc. Lagos del Country, Tepic 63175, Nayarit, Mexico
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13C Natural Isotope Abundance in Urothelium as a New Marker in the Follow-Up of Patients with Bladder Cancer. Cancers (Basel) 2022; 14:cancers14102423. [PMID: 35626027 PMCID: PMC9140021 DOI: 10.3390/cancers14102423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 05/08/2022] [Accepted: 05/10/2022] [Indexed: 02/01/2023] Open
Abstract
Bladder cancer (BC) is the most common urological malignancy and has a high incidence of recurrence. BC cells alter their nutrient uptake and metabolic pathways in order to continue the production of sufficient levels of ATP and metabolic intermediates for proliferation and survival. Changes in metabolic pathways regarding the rate of the enzymatic reaction and transport lead to differences in the content of natural isotopes (13C, 15N, 34S) between normal and cancerous tissues. The assessment of the stable isotopes of carbon, nitrogen, and sulfur in normal urothelium and bladder cancer samples was performed using Isotope Ratio Mass Spectrometry (IRMS). The natural abundance of 15N and 13C was decreased in bladder cancer samples when compared to normal urothelium. No significant correlation was observed in BC specimens depending on the tumor grade and stage. Samples derived from bladder tumors and normal urothelium had a different pattern of 15N and 13C isotope abundance. Decreased 13C natural isotopes in the normal urothelium of BC patients were significantly associated with a shorter DFS. Our results suggest that isotopic analysis of normal urothelium of BC patients can be used to predict bladder cancer recurrence.
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Domergue JB, Lalande J, Abadie C, Tcherkez G. Compound-Specific 14N/ 15N Analysis of Amino Acid Trimethylsilylated Derivatives from Plant Seed Proteins. Int J Mol Sci 2022; 23:ijms23094893. [PMID: 35563286 PMCID: PMC9105707 DOI: 10.3390/ijms23094893] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Revised: 04/18/2022] [Accepted: 04/26/2022] [Indexed: 02/01/2023] Open
Abstract
Isotopic analyses of plant samples are now of considerable importance for food certification and plant physiology. In fact, the natural nitrogen isotope composition (δ15N) is extremely useful to examine metabolic pathways of N nutrition involving isotope fractionations. However, δ15N analysis of amino acids is not straightforward and involves specific derivatization procedures to yield volatile derivatives that can be analysed by gas chromatography coupled to isotope ratio mass spectrometry (GC-C-IRMS). Derivatizations other than trimethylsilylation are commonly used since they are believed to be more reliable and accurate. Their major drawback is that they are not associated with metabolite databases allowing identification of derivatives and by-products. Here, we revisit the potential of trimethylsilylated derivatives via concurrent analysis of δ15N and exact mass GC-MS of plant seed protein samples, allowing facile identification of derivatives using a database used for metabolomics. When multiple silylated derivatives of several amino acids are accounted for, there is a good agreement between theoretical and observed N mole fractions, and δ15N values are satisfactory, with little fractionation during derivatization. Overall, this technique may be suitable for compound-specific δ15N analysis, with pros and cons.
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Affiliation(s)
- Jean-Baptiste Domergue
- Institut de Recherche en Horticulture et Semences, Université d’Angers, INRAe, 42 Rue Georges Morel, 49070 Beaucouzé, France; (J.-B.D.); (J.L.); (C.A.)
| | - Julie Lalande
- Institut de Recherche en Horticulture et Semences, Université d’Angers, INRAe, 42 Rue Georges Morel, 49070 Beaucouzé, France; (J.-B.D.); (J.L.); (C.A.)
| | - Cyril Abadie
- Institut de Recherche en Horticulture et Semences, Université d’Angers, INRAe, 42 Rue Georges Morel, 49070 Beaucouzé, France; (J.-B.D.); (J.L.); (C.A.)
| | - Guillaume Tcherkez
- Institut de Recherche en Horticulture et Semences, Université d’Angers, INRAe, 42 Rue Georges Morel, 49070 Beaucouzé, France; (J.-B.D.); (J.L.); (C.A.)
- Research School of Biology, Australian National University, Canberra, ACT 2601, Australia
- Correspondence:
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Stable Isotope Abundance and Fractionation in Human Diseases. Metabolites 2021; 11:metabo11060370. [PMID: 34207741 PMCID: PMC8228638 DOI: 10.3390/metabo11060370] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/01/2021] [Accepted: 06/05/2021] [Indexed: 01/02/2023] Open
Abstract
The natural abundance of heavy stable isotopes (13C, 15N, 18O, etc.) is now of considerable importance in many research fields, including human physiology. In fact, it varies between tissues and metabolites due to isotope effects in biological processes, that is, isotope discriminations between heavy and light isotopic forms during enzyme or transporter activity. The metabolic deregulation associated with many diseases leads to alterations in metabolic fluxes, resulting in changes in isotope abundance that can be identified easily with current isotope ratio technologies. In this review, we summarize the current knowledge on changes in natural isotope composition in samples (including various tissues, hair, plasma, saliva) found in patients compared to controls, caused by human diseases. We discuss the metabolic origin of such isotope fractionations and highlight the potential of using isotopes at natural abundance for medical diagnosis and/or prognostic.
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Foscari A, Leonarduzzi G, Incerti G. N uptake, assimilation and isotopic fractioning control δ 15N dynamics in plant DNA: A heavy labelling experiment on Brassica napus L. PLoS One 2021; 16:e0247842. [PMID: 33705458 PMCID: PMC7951814 DOI: 10.1371/journal.pone.0247842] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 02/12/2021] [Indexed: 12/02/2022] Open
Abstract
In last decades, a large body of evidence clarified nitrogen isotope composition (δ15N) patterns in plant leaves, roots and metabolites, showing isotopic fractionation along N uptake and assimilation pathways, in relation to N source and use efficiency, also suggesting 15N depletion in plant DNA. Here we present a manipulative experiment on Brassica napus var. oleracea, where we monitored δ 15N of purified, lyophilized DNA and source leaf and root materials, over a 60-days growth period starting at d 60 after germination, in plants initially supplied with a heavy labelled (δ 15NAir-N2 = 2100 mUr) ammonium nitrate solution covering nutrient requirements for the whole observation period (470 mg N per plant) and controlling for the labelled N species (ṄH4, ṄO3 and both). Dynamics of Isotopic Ratio Mass Spectrometry (IRMS) data for the three treatments showed that: (1) leaf and root δ 15N dynamics strictly depend on the labelled chemical species, with ṄH4, ṄO3 and ṄH4ṄO3 plants initially showing higher, lower and intermediate values, respectively, then converging due to the progressive NH4+ depletion from the nutrient solution; (2) in ṄH4ṄO3, where δ15N was not affected by the labelled chemical species, we did not observe isotopic fractionation associated to inorganic N uptake; (3) δ15N values in roots compared to leaves did not fully support patterns predicted by differences in assimilation rates of NH4+ and NO3-; (4) DNA is depleted in 15N compared to the total N pools of roots and leaves, likely due to enzymatic discrimination during purine biosynthesis. In conclusion, while our experimental setup did not allow to assess the fractionation coefficient (ε) associated to DNA bases biosynthesis, this is the first study specifically reporting on dynamics of specific plant molecular pools such as nucleic acids over a long observation period with a heavy labelling technique.
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Affiliation(s)
- Alessandro Foscari
- University of Trieste, Trieste, Italy
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Udine, Italy
| | - Giulia Leonarduzzi
- University of Trieste, Trieste, Italy
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Udine, Italy
| | - Guido Incerti
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Udine, Italy
- * E-mail:
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Wang Y, Wondisford FE, Song C, Zhang T, Su X. Metabolic Flux Analysis-Linking Isotope Labeling and Metabolic Fluxes. Metabolites 2020; 10:metabo10110447. [PMID: 33172051 PMCID: PMC7694648 DOI: 10.3390/metabo10110447] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 11/03/2020] [Accepted: 11/04/2020] [Indexed: 01/02/2023] Open
Abstract
Metabolic flux analysis (MFA) is an increasingly important tool to study metabolism quantitatively. Unlike the concentrations of metabolites, the fluxes, which are the rates at which intracellular metabolites interconvert, are not directly measurable. MFA uses stable isotope labeled tracers to reveal information related to the fluxes. The conceptual idea of MFA is that in tracer experiments the isotope labeling patterns of intracellular metabolites are determined by the fluxes, therefore by measuring the labeling patterns we can infer the fluxes in the network. In this review, we will discuss the basic concept of MFA using a simplified upper glycolysis network as an example. We will show how the fluxes are reflected in the isotope labeling patterns. The central idea we wish to deliver is that under metabolic and isotopic steady-state the labeling pattern of a metabolite is the flux-weighted average of the substrates’ labeling patterns. As a result, MFA can tell the relative contributions of converging metabolic pathways only when these pathways make substrates in different labeling patterns for the shared product. This is the fundamental principle guiding the design of isotope labeling experiment for MFA including tracer selection. In addition, we will also discuss the basic biochemical assumptions of MFA, and we will show the flux-solving procedure and result evaluation. Finally, we will highlight the link between isotopically stationary and nonstationary flux analysis.
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Affiliation(s)
- Yujue Wang
- Department of Medicine, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA; (Y.W.); (F.E.W.)
- Metabolomics Shared Resource, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ 08903, USA
| | - Fredric E. Wondisford
- Department of Medicine, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA; (Y.W.); (F.E.W.)
| | - Chi Song
- Division of Biostatistics, College of Public Health, The Ohio State University, Columbus, OH 43210, USA;
| | - Teng Zhang
- Department of Mathematics, University of Central Florida, Orlando, FL 32816, USA;
| | - Xiaoyang Su
- Department of Medicine, Rutgers-Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA; (Y.W.); (F.E.W.)
- Metabolomics Shared Resource, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ 08903, USA
- Correspondence: ; Tel.: +1-732-235-5447
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Rasmussen C, Hoffman DW. Intramolecular distribution of 13C/ 12C isotopes in amino acids of diverse origins. Amino Acids 2020; 52:955-964. [PMID: 32594254 DOI: 10.1007/s00726-020-02863-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 06/17/2020] [Indexed: 11/26/2022]
Abstract
Carbon stable isotope analysis can provide information about the origin and synthetic pathways that produce organic molecules, with applications in chemical, medical and (bio)geochemical sciences. The 13C/12C isotope ratios of organics such as amino acids are most commonly obtained as whole molecule averages. In this study, we apply proton nuclear magnetic resonance spectroscopy to conduct position-specific carbon isotope analyses of L-/D-alanine, L-threonine and L-histidine from different sources, in addition to molecule average stable isotope analyses obtained via mass spectrometry. Our results demonstrate that carbon isotope ratios can vary significantly between the individual carbon positions within an amino acid. For example, the β- and γ- carbons of L-threonine can differ in 13C/12C ratio by > 20 ‰. Comparisons of the position-specific and whole molecule average stable isotope abundances show that whole molecule analyses can mask the intramolecular isotope variation. These results provide the first experimentally measured position-specific isotope ratios for alpha and side chain carbons of alanine, threonine and histidine. Comparison with previous ab initio calculations of intramolecular equilibrium fractionation shows that the carbon isotope distributions are not at equilibrium, thus kinetic isotope effects play a significant role in amino acid synthesis. We hypothesize that position-specific 13C/12C isotope ratios provide an "isotopic fingerprint" that can give insight into the origin or synthesis pathway that formed an amino acid, and that this emerging analytical field will be a valuable addition to traditional stable isotope analysis.
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Affiliation(s)
- Cornelia Rasmussen
- Institute for Geophysics and Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA.
- University of Texas Center for Planetary Systems Habitability, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA.
| | - David W Hoffman
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
- University of Texas Center for Planetary Systems Habitability, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA
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Site-specific peak intensity ratio (SPIR) from 1D 2H/ 1H NMR spectra for rapid distinction between natural and synthetic nicotine and detection of possible adulteration. Anal Bioanal Chem 2019; 411:6427-6434. [PMID: 31321470 DOI: 10.1007/s00216-019-02023-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 06/04/2019] [Accepted: 07/05/2019] [Indexed: 02/07/2023]
Abstract
1H and 2H NMR spectra of 4 natural and synthetic nicotine samples were collected in a non-quantitative way and site-specific 2H/1H peak intensity ratio (SPIR) was calculated for 12 distinct sites of nicotine. Experimental results illustrated that the SPIRs at sites of 6, 2', and 5'β of natural nicotine were significantly different from those of the synthetic nicotine, and could be used for nicotine authentication as the measured SPIRs were indicative of the site-specific natural isotope fractionation. We demonstrated that this method could be applied to detect adulteration of natural nicotine with as low as 20% synthetic nicotine, without the need to measure the site-specific δD values, which usually required time-consuming quantitative 2H NMR and additional IRMS for the overall 2H/1H isotopic ratio determination. The distinguishable 2H/1H SPIRs of nicotine, which can be quickly measured by NMR in non-quantitative way, can serve as an attractive alternative tool for tobacco authentication. Graphical abstract.
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Fry B, Carter JF, Yamada K, Yoshida N, Juchelka D. Position-specific 13 C/ 12 C analysis of amino acid carboxyl groups - automated flow-injection analysis based on reaction with ninhydrin. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2018; 32:992-1000. [PMID: 29575301 PMCID: PMC6032851 DOI: 10.1002/rcm.8126] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 03/15/2018] [Accepted: 03/16/2018] [Indexed: 05/13/2023]
Abstract
RATIONALE The fundamental level of stable isotopic knowledge lies at specific atomic positions within molecules but existing methods of analysis require lengthy off-line preparation to reveal this information. An automated position-specific isotope analysis (PSIA) method is presented to determine the stable carbon isotopic compositions of the carboxyl groups of amino acids (δ13 CCARBOXYL values). This automation makes PSIA measurements easier and routine. METHODS An existing high-performance liquid chromatography (HPLC) gas handling interface/stable isotope ratio mass spectrometry system was modified by the addition of a post-column derivatisation unit between the HPLC system and the interface. The post-column reaction was optimised to yield CO2 from the carboxyl groups of amino acids by reaction with ninhydrin. RESULTS The methodology described produced δ13 CCARBOXYL values with typical standard deviations below ±0.1 ‰ and consistent differences (Δ13 CCARBOXYL values) between amino acids over a 1-year period. First estimates are presented for the δ13 CCARBOXYL values of a number of internationally available amino acid reference materials. CONCLUSIONS The PSIA methodology described provides a further dimension to the stable isotopic characterisation of amino acids at a more detailed level than the bulk or averaged whole-molecule level. When combined with on-line chromatographic separation or off-line fraction collection of protein hydrolysates the technique will offer an automated and routine way to study position-specific carboxyl carbon isotope information for amino acids, enabling more refined isotopic studies of carbon uptake and metabolism.
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Affiliation(s)
- Brian Fry
- Australian Rivers InstituteGriffith UniversityNathanQueensland4111Australia
| | - James F. Carter
- Queensland Health Forensic and Scientific ServicesCoopers PlainsQueensland4108Australia
| | - Keita Yamada
- Department of Chemical Science and EngineeringTokyo Institute of TechnologyYokohamaJapan
| | - Naohiro Yoshida
- Earth‐Life Science InstituteTokyo Institute of TechnologyTokyoJapan
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