Dataset Information

Synthesis of ¹⁵ N-labelled 3,5-dimethylpyridine.

ABSTRACT: ¹⁵ N-labelled pyridines are liquid- and solid-state nuclear magnetic resonance (NMR) probes for chemical and biological environments because their ¹⁵ N chemical shifts are sensitive to hydrogen-bond and protonation states. By variation of the type and number of substituents, different target pyridines can be synthesized exhibiting different pK_a values and molecular volumes. Various synthetic routes have been described in the literature, starting from different precursors or modification of other ¹⁵ N-labelled pyridines. In this work, we have explored the synthesis of ¹⁵ N ¹⁵ N-labelled pyridines using a two-step process via the synthesis of alkoxy-3,4-dihydro-2H-pyran as precursor exhibiting already the desired pyridine substitution pattern. As an example, we have synthesized 3,5-dimethylpyridine-¹⁵ N (lutidine-¹⁵ N) as demonstrated by ¹⁵ N-NMR spectroscopy. That synthesis starts from methacrolein, propenyl ether, and ¹⁵ N-labelled NH₄ Cl as nitrogen source.

SUBMITTER: Schubert M

PROVIDER: S-EPMC6973028 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Synthesis of 15 N-labelled 3,5-dimethylpyridine.

Schubert Mario M Limbach Hans-Heinrich HH Elguero José J

Journal of labelled compounds & radiopharmaceuticals 20191114 14

15 N-labelled pyridines are liquid- and solid-state nuclear magnetic resonance (NMR) probes for chemical and biological environments because their 15 N chemical shifts are sensitive to hydrogen-bond and protonation states. By variation of the type and number of substituents, different target pyridines can be synthesized exhibiting different pKa values and molecular volumes. Various synthetic routes have been described in the literature, starting from different pr ...[more]

PMID: 31677176

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Project description:BackgroundStable isotopically labelled organisms have found wide application in life science research including plant physiology, plant stress and defense as well as metabolism related sciences. Therefore, the reproducible production of plant material enriched with stable isotopes such as 13C and 15N is of considerable interest. A high degree of enrichment (> 96 atom %) with a uniformly distributed isotope (global labelling) is accomplished by a continuous substrate supply during plant growth/cultivation. In the case of plants, 13C-labelling can be achieved by growth in 13CO2(g) atmosphere while global 15N-labelling needs 15N- containing salts in the watering/nutrient solution. Here, we present a method for the preparation of 13C and 15N-labelled plants by the use of closed growth chambers and hydroponic nutrient supply. The method is exemplified with durum wheat.ResultsIn total, 330 g of globally 13C- and 295 g of 15N-labelled Triticum durum wheat was produced during 87 cultivation days. For this, a total of 3.88 mol of 13CO2(g) and 58 mmol of 15N were consumed. The degree of enrichment was determined by LC-HRMS and ranged between 96 and 98 atom % for 13C and 95-99 atom % for 15N, respectively. Additionally, the isotopically labelled plant extracts were successfully used for metabolome-wide internal standardisation of native T.durum plants. Application of an isotope-assisted LC-HRMS workflow enabled the detection of 652 truly wheat-derived metabolites out of which 143 contain N.ConclusionA reproducible cultivation which makes use of climate chambers and hydroponics was successfully adapted to produce highly enriched, uniformly 13C- and 15N-labelled wheat. The obtained plant material is suitable to be used in all kinds of isotope-assisted research. The described technical equipment and protocol can easily be applied to other plants to produce 13C-enriched biological samples when the necessary specific adaptations e.g. temperature and light regime, as well as nutrient supply are considered. Additionally, the 15N-labelling method can also be carried out under regular glasshouse conditions without the need for customised atmosphere.

Project description:Cobalamins (vitamin B12) are required by humans for their essential roles as enzyme cofactors in diverse metabolic processes. The four most common cobalamin vitamers are hydroxocobalamin (OHCbl), adenosylcobalamin (AdoCbl), methylcobalamin (MeCbl), and cyanocobalamin (CNCbl). Humans are not able to synthesise cobalamins de novo and thus must acquire them from external sources. Therefore, a reliable and robust analytical method to determine the cobalamins in dietary sources is highly required. For such a purpose, stable isotope dilution assays (SIDAs) with LC-MS/MS are most suited due to their superior sensitivity, specificity, and ability to compensate for matrix effects and analyte loss during sample work-up. However, a critical bottleneck for developing a SIDA method for cobalamins is the availability of stable isotope-labelled internal standards. In the present study, we harnessed the potential of Propionibacterium (P.) freudenreichii for the biosynthesis of 15N-labelled cobalamins. First, we developed a chemically defined medium (CDM) containing ammonium sulphate as a single nitrogen source except three essential vitamins that supported long-term stable growth of P. freudenreichii throughout continuous transfers. The CDM was further optimised for cobalamin production under different incubation schemes. With the optimised CDM and incubation scheme, fully 15N-labelled cobalamins were obtained in P. freudenreichii with a final yield of 312 ± 29 μg/L and 635 ± 102 μg/L, respectively, for [15N]-OHCbl and [15N]-AdoCbl. Additionally, an optimised incubation process under anaerobic conditions was successfully employed to produce specifically labelled [15N, 14N2]-cobalamins, with a yield of 96 ± 18 μg/L and 990 ± 210 μg/L, respectively, for [15N, 14N2]-OHCbl and [15N, 14N2]-AdoCbl. The labelled substances were isolated and purified by solid phase extraction and semi-preparative HPLC. Chemical modifications were carried out to produce [15N]-CNCbl and [15N]-MeCbl. Eventually, 15N-labelled compounds were obtained for the four cobalamin vitamers in high chromatographic and isotopic purity with desired 15N-enrichment and labelling patterns, which are perfectly suited for future use in SIDAs or other applications that require isotopologues.

Project description:BackgroundThe use of enriched stable isotopes is of outstanding importance in chemical metrology as it allows the application of isotope dilution mass spectrometry (IDMS). Primary methods based on IDMS ensure the quality of the analytical measurements and traceability of the results to the international system of units. However, the synthesis of isotopically labelled molecules from enriched stable isotopes is an expensive and a difficult task. Either chemical and biochemical methods to produce labelled molecules have been proposed, but so far, few cost-effective methods have been described.ResultsThe aim of this study was to use the microalgae Chlamydomonas reinhardtii to produce, at laboratory scale, 15N-labelled amino acids with a high isotopic enrichment. To do that, a culture media containing 15NH4Cl was used. No kinetic isotope effect (KIE) was observed. The labelled proteins biosynthesized by the microorganism were extracted from the biomass and the 15N-labelled amino acids were obtained after a protein hydrolysis with HCl. The use of the wall deficient strain CC503 cw92 mt+ is fit for purpose, as it only assimilates ammonia as nitrogen source, avoiding isotope contamination with nitrogen from the atmosphere or the reagents used in the culture medium, and enhancing the protein extraction efficiency compared to cell-walled wild type Chlamydomonas. The isotopic enrichment of the labelled amino acids was calculated from their isotopic composition measured by gas chromatography mass spectrometry (GC-MS). The average isotopic enrichment for the 16 amino acids characterized was 99.56 ± 0.05% and the concentration of the amino acids in the hydrolysate ranged from 18 to 90 µg/mL.ConclusionsPreviously reported biochemical methods to produce isotopically labelled proteins have been applied in the fields of proteomics and fluxomics. For these approaches, low amounts of products are required and the isotopic enrichment of the molecules has never been properly determined. So far, only 13C-labelled fatty acids have been isolated from labelled microalga biomass as valuable industrial products. In this study, we propose Chlamydomonas reinhardtii CC503 as a feasible microorganism and strain to produce labelled biomass from which a standard containing sixteen 15N-labelled amino acids could be obtained.

Dataset Information

Synthesis of ¹⁵ N-labelled 3,5-dimethylpyridine.

Publications

Synthesis of <sup>15</sup> N-labelled 3,5-dimethylpyridine.

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