Category Archives: Methods & Applications

Posts describing the use of the nmr spectroscopy (MRS) methodology, either from a practical point of view (how to perform certain experiment), or from a more theoretical perspective (description of techniques and their application).

Master thesis on NMR methods to mesure residual proton-carbon dipolar couplings in small molecules

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Last September I defended my Master thesis entitled: “Medida de Acoplamientos Dipolares Residuales en Moléculas Orgánicas”

In recent years the use of Residual Dipolar Couplings (RDCs) has had a huge impact on the structure determination of biological macromolecules by Nuclear Magnetic Resonance (NMR). Its usefulness in determining the structure of small/medium-size organic compounds is increasingly more recognized. Continue reading Master thesis on NMR methods to mesure residual proton-carbon dipolar couplings in small molecules →

Accurate measurement of small heteronuclear coupling constants from pure-phase α/β HSQMBC cross-peaks

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“Accurate measurement of small heteronuclear coupling constants from pure-phase α/β HSQMBC”, by Sergi Gil, Juan Félix Espinosa and Teodor Parella; Journal of Magnetic Resonance 213, 1, 145-150 (2011). DOI:10.1016/j.jmr.2011.09.036

A simple proton-selective α/β-HSQMBC experiment is proposed for the accurate measurement of long-range proton–carbon coupling constants (nJCH) in small molecules without need for an individualized and time-consuming post-processing fitting procedure. Continue reading Accurate measurement of small heteronuclear coupling constants from pure-phase α/β HSQMBC cross-peaks →

ECOMETABOLOMICS: Metabolomics in Ecological Studies

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“Strong relationship between elemental stoichiometry and metabolome in plants” Albert Rivas-Ubach, Jordi Sardans, Miriam Pérez-Trujillo, Marc Estiarte and Josep Peñuelas.  PNAS, February 2012. DOI: 10.1073/pnas.1116092109

Shifts in the elemental stoichiometry of organisms in response to their ontogeny and to changing environmental conditions should be related to metabolomic changes because elements operate mostly as parts of molecular compounds. Here we show this relationship in leaves of Erica multiflora throughout their seasonal development and in response to moderate experimental field conditions of drought and warming. Continue reading ECOMETABOLOMICS: Metabolomics in Ecological Studies →

Measurement of the magnitude and the sign of small nJCH on protonated and non-protonated carbons

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“A definitive NMR solution for the simple and accurate measurement of the magnitude and the sign of small heteronuclear coupling constants on protonated and non-protonated carbons”, by Josep Saurí, Juan Félix Espinosa and Teodor Parella; Angew. Chem. Int. Ed. (2012) DOI: 10.1002/anie.201108959

The measurement of long-range proton carbon coupling constants in natural-abundance molecules has always been a tranding topic for the NMR community. Despite the extensive number of NMR techniques that have been developed, there are still remain two unsolved problems pertaining to non-protonated carbons, namely, a) and accurate measurement of very small coupling constants (less than 2-3 Hz) , and b) the absence of a general and robust approach to determine the sign of the coupling. Continue reading Measurement of the magnitude and the sign of small nJCH on protonated and non-protonated carbons →

HPLC-DAD-(SPE)-NMR/MS II: fundamentals and working modes

Methods & Applications

This hyphenated technique combines HPLC with three complementary detection techniques – NMR Spectroscopy, Mass Spectrometry and Diode Array Detection. It is a highly rich information source, which can be obtained by one-shot analysis.

There are three different modes of work: Flow-NMR, Stop-Flow and SPE-storage; and depending on the scientific problem one or another will be the most adequate. Continue reading HPLC-DAD-(SPE)-NMR/MS II: fundamentals and working modes →

CHIRAL METABONOMICS: Giving Metabonomics a Chiral Dimension

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“Chiral Metabonomics: 1H NMR-Based Enantiospecific Differentiation of Metabolites in Human Urine via Direct Cosolvation with β-Cyclodextrin” Míriam Pérez-Trujillo, John C. Lindon, Teodor Parella, Hector C. Keun, Jeremy K. Nicholson and Toby J. Athersuch. Analytical Chemistry, February 2012 DOI:10.1021/ac203291d

Differences in molecular chirality remain an important issue in drug metabolism and pharmacokinetics for the pharmaceutical industry and regulatory authorities and chirality is an important feature of many endogenous metabolites. We present a 1H NMR-based method for the rapid, direct differentiation and identification of chiral drug enantiomers in human urine without pre-treatment of any kind. Continue reading CHIRAL METABONOMICS: Giving Metabonomics a Chiral Dimension →

HPLC-DAD-(SPE)-NMR/MS I: all in one technique for the analysis of mixtures

Methods & Applications

The combination of liquid chromatography with three complementary detection techniques – NMR Spectroscopy, Mass Spectrometry and Diode Array Detection, provides highly rich information in a one-shot analysis.

The possibility of a post-chromatography storage /concentration of the chromatographic peaks of interest, using a SPE (Solid Phase Extraction) system, together with the use of cool probes,  increases the sensitivity of the NMR detection.

Continue reading HPLC-DAD-(SPE)-NMR/MS I: all in one technique for the analysis of mixtures →

Measurement of long-range proton-carbon coupling constants from pure in-phase 1D multiplets

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“Measurement of long-range proton-carbon constants from pure in-phase 1D multiplets”, by Juan F. Espinosa, Paloma Vidal, Teodor Parella and Sergi Gil: Magnetic Resonance in Chemistry 49, 502-507 (2011). DOI:10.1002/mrc.2782

A double-selective variant of the SELINCOR pulse sequence yields 1D proton multiplets that exhibit pure absortive in-phase lineshapes for precise measurement of specific long-range proton-carbon coupling constants in small organic molecules at natural abundance. Continue reading Measurement of long-range proton-carbon coupling constants from pure in-phase 1D multiplets →

What is DNP? Obtaining enhanced NMR signals for in-vitro and in-vivo applications

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Dynamic Nuclear Polarization is the method for obtaining strongly polarised nuclear spins, resulting in enhanced NMR signals for 13C and 15N nuclei in solution-state

Our NMR facility (SeRMN) has recently installed a HyperSense® (Oxford Instruments), a new instrument capable of delivering a huge sensitivity enhancement for your in-vitro and in-vivo applications allowing an easy and quick switching between both applications.

Liquid-state NMR spectroscopy is an important technique into a wide range of applications. However, it is limited by an intrinsically lack of sensitivity due to the low gyromagnetic ratio and natural abundance of the nuclei usually under study (13C, 15N, etc.) as compared with other analytical methods. Continue reading What is DNP? Obtaining enhanced NMR signals for in-vitro and in-vivo applications →

Hyperpolarized 13C magnetic resonance metabolic imaging in a mouse brain glioma model

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Magnetic resonance spectroscopic imaging (MRSI) of hyperpolarized [1-13C]pyruvate is a promising technique to noninvasively monitor metabolic changes in vivo. This method uses dynamic nuclear polarization (DNP) techniques to obtain tens of thousands fold enhancement in the polarization of [1-13C]pyruvate and its metabolic products, like lactate, providing sufficient MR signal for high spatial and temporal resolution spectroscopic imaging of these metabolites. Continue reading Hyperpolarized 13C magnetic resonance metabolic imaging in a mouse brain glioma model →