These are short reports about the research activities carried out at the SeRMN.
In them we describe the work done in collaboration with research groups, to summarize communications presented at scientific meetings, to report visits and stages at other laboratories or facilities, and to comment the meetings and workshops we have attended.
Simultaneous Enantiospecific Detection of Multiple Compounds in Mixtures using NMR Spectroscopy, by Lars T. Kuhn, Kumar Motiram-Corral, Toby J. Athersuch, Teodor Parella, Míriam Pérez-Trujillo*
Chirality plays a fundamental role in nature, but its detection and quantification still face many limitations. To date, the enantiospecific analysis of mixtures necessarily requires prior separation of the individual components. The simultaneous enantiospecific detection of multiple chiral molecules in a mixture represents a major challenge, which would lead to a significantly better understanding of the underlying biological processes; e.g. via enantiospecifically analysing metabolites in their native environment. Here, we report on the first in situ enantiospecific detection of a thirty‐nine‐component mixture. As a proof of concept, eighteen essential amino acids at physiological concentrations were simultaneously enantiospecifically detected using NMR spectroscopy and a chiral solvating agent. This work represents a first step towards the simultaneous multicomponent enantiospecific analysis of complex mixtures, a capability that will have substantial impact on metabolism studies, metabolic phenotyping, chemical reaction monitoring, and many other fields where complex mixtures containing chiral molecules require efficient characterisation.
Simultaneous enantiospecific detection of a mixture of amino acids by NMR spectroscopy
Dibromomethane (DBM) and 1,2‐dibromoethane (DBA) are two brominated volatile contaminants used in several industrial applications which are often detected in groundwater. The electrochemical degradation of DBM and DBA was studied at different cathode potentials (−0.8, −1 and −1.2 V versus Standard Hydrogen Electrode) in aqueous solution using an inexpensive graphite fiber brush electrode.
The degradation followed first‐order kinetics with respect to the nominal concentration of the brominated compounds, and the kinetic constant increased concomitantly with the decrease of the cathode potential. During the electrochemical dehalogenation 96.8% and 99.8% of the bromide in DBM and DBA was released as bromine ions, respectively. The main non‐brominated compounds detected during the degradation of DBM and DBA were methane and ethene, respectively. In addition, traces of formic acid for DBM and acetic acid for DBA degradation were detected by NMR spectroscopy. The non‐toxicity of the effluent was confirmed by a Microtox test. The efficient electrochemical degradation of DBM and DBA and the lack of toxic products open the door for a simple and non‐toxic electrochemical approach for removing aliphatic brominated compounds from aquifers and other water sources.
31P-NMR Metabolomics Revealed Species-Specific Use of Phosphorous in Trees of a French Guiana Rainforest, by Gargallo-Garriga, A.; Sardans, J.; Llusià, J.; Peguero, G.; Asensio, D.; Ogaya, R.; Urbina, I.; Langenhove, L.V.; Verryckt, L.T.; Courtois, E.A.; Stahl, C.; Grau, O.; Urban, O.; Janssens, I.A.; Nolis, P.; Pérez-Trujillo, M.; Parella, T.; Peñuelas, J. Molecules2020, 25, 3960. https://doi.org/10.3390/molecules25173960
Productivity of tropical lowland moist forests is often limited by availability and functional allocation of phosphorus (P) that drives competition among tree species and becomes a key factor in determining forestall community diversity. We used non-target 31P-NMR metabolic profiling to study the foliar P-metabolism of trees of a French Guiana rainforest. The objective was to test the hypotheses that P-use is species-specific, and that species diversity relates to species P-use and concentrations of P-containing compounds, including inorganic phosphates, orthophosphate monoesters and diesters, phosphonates and organic polyphosphates. We found that tree species explained the 59% of variance in 31P-NMR metabolite profiling of leaves. A principal component analysis showed that tree species were separated along PC 1 and PC 2 of detected P-containing compounds, which represented a continuum going from high concentrations of metabolites related to non-active P and P-storage, low total P concentrations and high N:P ratios, to high concentrations of P-containing metabolites related to energy and anabolic metabolism, high total P concentrations and low N:P ratios. These results highlight the species-specific use of P and the existence of species-specific P-use niches that are driven by the distinct species-specific position in a continuum in the P-allocation from P-storage compounds to P-containing molecules related to energy and anabolic metabolism.
Herein, we perform for the first time a preliminary NMR and computational study of the spiroglycol structure. Spiroglycol is a highly symmetrical molecule, but it should be chiral due to the presence of a chiral axis. The presence of two enantiomers was demonstrated performing NMR enantiodifferentiation experiments using α,α′-bis(trifluoromethyl)-9,10-anthracenedimethanol (ABTE) as a chiral solvating agent (CSA). The addition of 0.6 equiv of ABTE allows the differentiation of several spiroglycol proton signals. The lack of resolution observed in the proton spectrum can be tackled through the corresponding 13C NMR spectrum where a significant enantiodifferentiation at the spirocarbon atom was observed. In order to physically separate both enantiomers, a SPG derivatization with camphorsulfonic acid and Mosher’s acid was performed affording the corresponding diastereoisomeric ester mixtures. Computations performed with the Gaussian16 package showed that the enantiodifferentiation is mainly due to the different compound thermodynamics stability.
ABSTRACT:The detection of ultra-long-range (4JCHand higher) heteronuclear connectivities can complement the conventionaluse of HMBC/HSQMBC data in structure elucidation NMR studies of proton-deficient natural products, where two-bond andthree-bond correlations are usually observed. The performance of the selHSQMBC experiment with respect to its broadbandHSQMBC counterpart is evaluated. Despite its frequency-selectivity nature, selHSQMBC efficiently prevents any unwanted signalphase and intensity modulations due to passive proton−proton coupling constants typically involved in HSQMBC. As a result,selHSQMBC offers a significant sensitivity enhancement and provides pure in-phase multiplets, improving the detection levels forshort- and long-range cross-peaks corresponding to small heteronuclear coupling values. This is particularly relevant for experimentsoptimized to smallnJCHvalues (2−3 Hz), referred to as LR-selHSQMBC, where key cross-peaks that are not visible in the equivalentbroadband LR-HSQMBC spectrum can become observable in optimum conditions.
We are recruiting an Early Stage Researcher to work on a decision-support system based on MRSI data at 3T, for glioblastoma therapy response follow- up, as part of the INSPiRE-MED European project.
We seek a highly motivated and qualified individual as Early Stage Researcher for a three-year applied research project. The successful candidate will contribute to the development of advanced biomedical research tools in the field of Magnetic Resonance Spectroscopy and Imaging, and its application to the clinical day-to-day practice.
Project description: This position is one of the 15 ESR positions of the INSPiRE-MED European Training Network, which focuses on the development of Magnetic Resonance Spectroscopy (MRS) and MR Spectroscopic Imaging (MRSI) combined with Positron Emission Tomography (PET), enhanced by machine learning techniques.
The main aim of the PhD project (ESR12) will be development of a Machine Learning medical decision-support system based on MRSI data at 3T, for glioblastoma therapy response follow-up.
The
ESR will develop a novel medical decision support system (MDSS)
focused on glioblastoma therapy response follow-up, based on magnetic
resonance spectroscopic imaging (MRSI) data, able to take and process
data from multiple MRSI formats and centres. For each patient’s
MRSI, the MDSS should deliver a nosological or classification image,
ready to be fused with images of other MR modalities from the same
patient. The DSS will be integrated into the interface of the
academic version of jMRUI, in a way that allows clinicians evaluate
the system with their data. An important part of of the project will
be the incorporation of automated MRSI artifact detection and removal
tools.
Kumar Motiram-Corral presented a poster titled “Implementing one-shot multiple-FID acquisition into homonuclear and heteronuclear NMR experiments” at SMASH 19 in Porto (Portugal).
To date, time-efficient approaches are a challenged task for spectroscopists. The goal is to obtain chemical information reducing experimental time without considerably losing of sensitivity.
Different time-efficient approaches have been described over the years. Time sharing (Parella et. al.) tactic acquires the 15N and 13C nuclei in the same spectrum in spectrometers which have a triple channel hardware configuration[1]. Non-Uniform Sampling (NUS) [2] algorithm has achieved a substantial reduction of experimental time reducing the number of t1 increments needed by multidimensional experiments. Recently, NOAH [3] (NMR by ordered Acquisition using 1H detection) has been developed by Kupče (Bruker Co.) and Claridge (University of Oxford) provides the way to get proper experiments in different spectra with the same spectral quality.
[4]MFA (Multiple FID Acquisition) consists in obtaining up to four different experiments decreasing close to 60% of time. MFA provides a new novel proof concept of COSY, TOCSY and HMBC experiments in small molecules. Actually, MFA strategy was proposed many years ago with the COCONOSY experiment [5-7], which could be collected 2D COSY and NOESY data with a single pulse scheme. [4]MFA has also been implemented in magic-angle-spinning solid-state NMR experiments devoted for biomacromolecules using standard spectrometer configuration. Despite its limitations related to the use of long acquisition of free-induction decays (FIDs) to accurately digitalize the data and the mandatory use of long phase cycles for convenient pathway selection, nowadays, the use of pulsed field gradients (PFGs) is the solution for this drawback. [4]MFA is based on the relaxation of the remaining transverse magnetization, which usually relaxes to its original magnetization, can be manipulated by an appropriate additional mixing process and recorded again to obtain a second or third NMR data provided that T2 (transverse relaxation times) are long enough. [4]Its main advantage is that each experiment is acquired in a different display. [4]MFA is a powerful experiment for the sequential structural assignment of a whole spin system without ambiguities. This method is also useful for selective experiments as SE-TOCSY.
References:
Nolis, P., Pérez, M., & Parella, T. (2006). Time-sharing evolution and sensitivity enhancements in 2D HSQC-TOCSY and HSQMBC experiments. Magnetic Resonance in Chemistry, 44, 11, 1031-1036, 2006
K. Kazimierczuk and V. Y. Orekhov , Angew. Chem., Int. Ed., 2011, 50 , 5556 -5559
Kupče, E., & Claridge, T. D. W. (2018). Molecular structure from a single NMR supersequence. Chemical Communications, 54, 7139-7142, 2018.
Motiram-Corral, K., Pérez-Trujillo, M., Nolis, P., & Parella, T. (2018). Implementing one-shot multiple-FID acquisition into homonuclear and heteronuclear NMR experiments. Chemical Communications, 54(96), 13507–13510, 2018.
A. Z. Gurevich , I. L. Barsukov , A. S. Arseniev and V. F. Bystrov , J. Magn. Reson.,56, 471 -478, 1984.
C. A. G. Haasnoot , F. J. M. van de Ven and C. W. Hilbers , J. Magn. Reson., 56 , 343 -349, 1984.
J. Cavanagh and M. Rance , J. Magn. Reson., 14 , 408 -414, 1990.
How to measure long‐range proton‐carbon coupling constants from 1H‐selective HSQMBC experiments, by Josep Saurí, Pau Nolis and Teodor Parella. Magn. Reson. Chem. 2019. Early View, DOI: https://onlinelibrary.wiley.com/doi/10.1002/mrc.4928
Heteronuclear long‐range scalar coupling constants (nJCH) are a valuable tool for solving problems in organic chemistry and are especially suited for stereochemical and configurational analyses of small molecules and natural products. This tutorial will focus on the step‐by‐step implementation of several 2D 1H frequency selective HSQMBC experiments for the easy and accurate measurement of either the magnitude or both the magnitude and the sign of long‐range nJCH couplings. The performance of these experiments will be showcased with several scenarios in a range of different experimental conditions.
Bruker pulse program code for selHSQMBC experiments available here.
Bruker pulse program code for selHSQMBC-TOCSY experiment available here.
Some of the SeRMN staff will present our last research works at the annual meeting of the European magnetic resonance community ISMAR EUROMAR 2019 Conference that will take place from 25th to 30th August in Berlin. Find below a summary of our contributions.
Speeding-up NMR molecular analysis is an
important research field which has been continuously advancing since NMR early
days. The relevant benefits are clear and evident: reduce the time per analysis
directly reduce its cost and gaining spectrometer time to analyze new samples. Many
interesting tools and concepts have been appearing in last decades. Concretely,
our experience focuses on the development of new NMR experiments using TS
(Time-Shared), SA (Spectral Aliasing) and MFA (Multiple Fid Acquisition). MFA
strategy is an interesting strategy that allows the acquisition of different structural
information in a single experiment. Basically, MFA experiments consist in the
design of pulse sequence experiments which accommodate several acquisition
windows per experi-ment, each registering different relevant information for
the structural molecular character-ization. The methodology brings a
corresponding important time benefit. Last year, we have reported several new
NMR experiments designed with MFA stratey and herein we would present the most
relevant achievements. The overall discussion will be mainly focused on the
sensitivity gains per time unit of the presented experiments.
The
3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane
commonly named pentaspiroglycol
(PSG) or spiroglycol (SPG) is a high molecular weight rigid alicy-clic diol widely used in the chemical
industry. SPG has no hazardous classification, it is not mutagenic and is a safe alternative to
Bisphenol A, a well-known chemical which is rising concern due to his proved endocrine
disruptor activity. Moreover, some of the SPG main applications are focused on epoxy resins,
liquid polyester resins, radiation curing resins and
in polymer film material field. However, the spiroglycol structure,
configuration and conformation
have never been deeply studied. Herein,
we perform for the first time a preliminary NMR and computational study of the spiroglycol structure. SPG is a highly
symmetrical molecule but it should be chiral due to
the presence of a chiral axis. The presence of two enantiomers was demonstrated
per-forming NMR
enantiodifferentiation experiments using α,α’-bis(trifluoromethyl)-9,10-an-thracenedimethanol (ABTE) as chiral
solvating agent (CSA). The addition of 0.6 equivalents of ABTE allows the differentiation of
several spiroglycol proton signals. The lack of resolu-tion observed in the proton spectrum can be
tackled through the corresponding 13C NMR spectrum
where a significant enantiodifferentiation at the spirocarbon atom was observed.In order to physically separate both
enantiomers, a SPG derivatization with camphor-sulphonic
acid was performed affording the corresponding diastereoisomeric ester mixture.
The 23rd May 2019 at 12:45, Sala d’Actes de la Facultat de Ciències de la UAB, I will present my work on “Implementing one-shot multiple-FID acquisition into homonuclear and heteronuclear NMR experiments” at the Novena Edició de les Jornades Doctorals by the PhD Chemistry Program and the Chemistry Department (Meeting program).
