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).

Recyclable Mesoporous Organosilica Nanoparticles (MSN) for Asymmetric Organocatalysis

Li, Hao, Míriam Pérez-Trujillo, Xavier Cattoën & Roser Pleixats. 2019. Recyclable Mesoporous Organosilica Nanoparticles Derived from Proline-Valinol Amides for Asymmetric Organocatalysis. ACS Sustainable Chemistry & Engineering 7(17). 14815-14828. DOI: 10.1021/acssuschemeng.9b02838

This is the first report on the obtention of functionalized MSN by a co-condensation procedure with a structurally complex chiral precursor. The functionalized MSN have been characterized by elemental analysis, 29Si and 13C CP MAS NMR, transmission electron microscopy, scanning electron microscopy, N2-sorption measurements, dynamic light scattering, ζ-potential, and powder X-ray diffraction. We have evaluated the activity of these materials as recyclable catalysts in the asymmetric aldol reaction. The use of organosilica nanoparticles reduces the problems of diffusion and low reaction rates encountered with bulk organosilicas.

SeRMN contribution at SMASH 2019

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: 

  1. 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
  2. K. Kazimierczuk and V. Y. Orekhov , Angew. Chem., Int. Ed., 2011, 50 , 5556 -5559
  3. Kupče, E., & Claridge, T. D. W. (2018). Molecular structure from a single NMR supersequence. Chemical Communications, 54, 7139-7142, 2018.
  4. 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.
  5. A. Z. Gurevich , I. L. Barsukov , A. S. Arseniev and V. F. Bystrov , J. Magn. Reson., 56, 471 -478, 1984. 
  6. C. A. G. Haasnoot , F. J. M. van de Ven and C. W. Hilbers , J. Magn. Reson.56 , 343 -349, 1984. 
  7. J. Cavanagh and M. Rance , J. Magn. Reson., 14 , 408 -414, 1990. 

SeRMN contributions at ISMAR EUROMAR 2019 Conference

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.

Pau Nolis presents a poster entitled “Reducing experimental time using Multiple Fid Acquisition (MFA) strategy” (P341). Pau Nolis, Kumar Motiram-Corral, Miriam Pérez-Trujillo, Teodor Parella.

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.

Eva Monteagudo presents a poster entitled “Enantiodifferentiation Study of Spiroglycol Chirality” (P306). Eva Monteagudo, Albert Virgili, Teodor Parella, Carles Jaime.

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.

Beneficial effects of Uric Acid Treatment After Stroke in Hypertensive Rats

Jiménez-Xarrié, Elena, Belén Pérez, Ana Paula Dantas, Lídia Puertas-Umbert, Joan Martí-Fabregas, Ángel Chamorro, Anna Maria Planas, Elisabet Vila, Francesc Jiménez-Altayó. 2018. Uric Acid Treatment After Stroke Prevents Long-Term Middle Cerebral Artery Remodelling and Attenuates Brain Damage in Spontaneously Hypertensive Rats. Translational Stroke Research. DOI: 10.1007/s12975-018-0661-8

Hypertension is the most important modifiable risk factor for stroke and is associated with poorer post-stroke outcomes. The antioxidant uric acid is protective in experimental normotensive ischaemic stroke. However, it is unknown whether this treatment exerts long-term protection in hypertension. The authors aimed to evaluate the impact of transient intraluminal middle cerebral artery (MCA) occlusion (90min)/reperfusion (1–15 days) on brain and vascular damage progression in adult and spontaneously hypertensive rats (SHR) treated with uric acid. Ischaemic brain damage was assessed longitudinally with magnetic resonance imaging at the Nuclear Magnetic Resonance Service of the Universitat Autònoma de Barcelona.

In SHR rats, more severe brain damage and poorer neurofunctional outcomes were coupled to higher cortical cerebral blood flow at the onset of reperfusion, a transient increase in oxidative stress and long-lasting stroke-induced MCA hypertrophic remodelling. Thus, stroke promotes larger brain and vascular damage in hypertensive rats that persists for long-time. Uric acid administered during early reperfusion attenuated short- and long-term brain injuries in both normotensive and hypertensive rats, an effect that was associated with abolishment of the acute oxidative stress response and prevention of stroke-induced long lasting MCA remodelling in hypertension. These results suggest that uric acid might be an effective strategy to improve stroke outcomes in hypertensive subjects.

MRI/MRS in treated Alzheimer mice

Montoliu-Gaya, Laia, Jofre Güell-Bosch, Gisela Esquerda-Canals, Alejandro R. Roda, Gabriel Serra-Mir, Silvia Lope-Piedrafita, José Luís Sánchez-Quesada & Sandra Villegas. 2018. Differential effects of apoE and apoJ mimetic peptides on the action of an anti-Aβ scFv in 3xTg-AD mice. Biochemical Pharmacology 155. 380–392. DOI: 10.1016/j.bcp.2018.07.012

Anti-Aβ immunotherapy has emerged as a promising approach to treat Alzheimer’s disease (AD). The single-chain variable fragment scFv-h3D6 is an anti-Aβ antibody fragment that lacks the Fc region, which is associated with the induction of microglial reactivity by the full-length monoclonal antibody bapineuzumab. ScFv-h3D6 was previously shown to restore the levels of apolipoprotein E (apoE) and apolipoprotein J (apoJ) in a tripletransgenic- AD (3xTg-AD) mouse model. Since apoE and apoJ play an important role in the development of AD, we aimed to study the in vivo effect of the combined therapy of scFv-h3D6 with apoE and apoJ mimetic peptides (MPs).

Continue reading MRI/MRS in treated Alzheimer mice

Exopolysaccharides from olive brines could reduce the adhesion of ETEC K88 to intestinal epithelial cells

Zhu, Yanan, Gemma González-Ortiz, Rufino Jiménez-Díaz, Míriam Pérez-Trujillo, Teodor Parella, Paola López-Colom & Susana María Martín-Orúe. 2018. Exopolysaccharides from olive brines could reduce the adhesion of ETEC K88 to intestinal epithelial cells. Food & Function 9(7). 3884–3894. DOI: https://doi.org/10.1039/c8fo00690c

This study aims to explore the biological functions of the isolated exopolysaccharides (EPSs) produced during the industrial fermentation of olives against enterotoxigenic E. coli (ETEC) K88. Exopolysaccharides were isolated from five industrial fermenters. Analysis of their monosaccharide composition by GLC revealed that the main components were glucose (27%–50%) and galactose (23%–33%) followed by rhamnose (4–23%) and arabinose (6–17%). The 1H NMR spectrum showed a very similar profile between samples, and a more in-depth analysis revealed the presence of an α-pyranose in the form of α-D-Glcp-(1→) and two different α-furanoses, with chemicals shift values, suggesting the presence of α-D-Glcf and α-D-Galf. Miniaturized in vitro tests demonstrated the ability of EPS samples to attach specifically to ETEC K88 (P < 0.05) with variable intensities. The competition test did not show the ability to block the ETEC K88 adhesion to IPEC-J2 cells; however, in the displacement test, all EPS samples were shown to effectively remove the pathogens attached to the cells (P < 0.01).

These results suggest that the EPSs produced during the fermentation of table green olives could interfere with the attachment of opportunistic pathogens onto the intestinal epithelial cells. This would open the possibility of novel functional properties for this traditional Mediterranean fermented food and for the isolated EPSs as candidates for nutraceutics to be used in human and/or animal diets in the prevention and treatment of ETEC diarrhoea.

PhD Thesis: Development of Resolution-Enhanced NMR Techniques for Improved Small Molecules Structural Analysis

Last July 14th 2018 Núria Marcó defended her PhD Thesis entitled: Development of Resolution-Enhanced NMR Techniques for Improved Small Molecules Structural Analysis

The present doctoral thesis is framed within the field of Nuclear Magnetic Resonance (NMR) spectroscopy.

NMR spectroscopy is an analytic technique and, therefore, one of its main objectives is to unravel the correct structure of the molecules analyzed.This present doctoral thesis  is focused on this main objective. This work consists in a compendium of 7 publications, written in several prestigious scientific journals, that develop in depth the efficient and accurate determination of the constitution, configuration and conformation of small molecules thanks to the application of resolution improvements techniques.

Continue reading PhD Thesis: Development of Resolution-Enhanced NMR Techniques for Improved Small Molecules Structural Analysis

NEW BOOK RELEASE: “Preclinical MRI methods and protocols”

García Martín, María Luisa & Pilar López Larrubia (eds.). 2018. Preclinical MRI. Methods in Molecular Biology series. Springer New York. DOI: 10.1007/978-1-4939-7531-0

This book was conceived with the idea of providing an update on a wide variety of preclinical MRI methods and protocols to help technicians and researchers interested in this technology. The basics of MRI physics are introduced, followed by chapters describing updated methodology and protocols for some standard and more advanced MRI techniques covering diffusion, perfusion, functional imaging, in-vivo spectroscopy (proton and heteronuclear), susceptibility contrast MRI… The book also contains some chapters where some applications of those methods are illustrated in animal models of several diseases including cancer, stroke and neurodegeneration. Protocols are described in a step-by-step approach, with interesting notes and tips at the end of each chapter, which -a priori- should allow the new worker to obtain successful results with the first attempt ;o) .

PhD Thesis: New Applications of Covariance NMR and Experimental Development for Measurements of Homonuclear Coupling Constants in Overlapping Signals

On 21st March 2018 I sucessfully defended my PhD Thesis entitled: “New Applications of Covariance NMR and Experimental Development for Measurements of Homonuclear Coupling Constants in Overlapping Signals” (ISBN: 9788449079252), supervised by Dr. Teodor Parella and Dr. Pau Nolis, and obtained the degree of Ph.D. in Chemistry at the Department of Chemistry, Universitat Autònoma de Barcelona.

The thesis can be downloaded in PDF format from the TDX repository and from the TESEO repository.

Accurate measurement of proton homonuclear coupling constants in overlapped signals by using a doubly-selective TOCSY G-SERF experiment.

Abstract

The experimental results obtained in this thesis are presented in the form of three papers published in NMR specialised scientific peer-reviewed journals.

  • Exploring the use of Generalized Indirect Covariance to Reconstruct Pure shift NMR Spectra: Current Pros and Cons. André Fredi, Pau Nolis, Carlos Cobas, Gary E. Martin and Teodor Parella. Journal of Magnetic Resonance, Volume 266, May 2016, Pages 16-22. DOI: 10.1016/j.jmr.2016.03.003
  • Access to experimentally infeasible spectra by pure-shift NMR covariance. André Fredi, Pau Nolis, Carlos Cobas and Teodor Parella. Journal of Magnetic Resonance, Volume 270, September 2016, Pages 161-168. DOI: 10.1016/j.jmr.2016.07.010
  • Accurate measurement of JHH in overlapped signals by a TOCSY‐edited SERF Experiment. André Fredi, Pau Nolis and Teodor Parella. Magnetic Resonance in Chemistry, Volume 55, Issue 6, June 2017, Pages 525-529. DOI: 10.1002/mrc.4572

The first two articles deal with the use of covariance NMR as a general method to generate novel psNMR spectra. The last work describes a new selTOCSY G-SERF experiment, for accurately measuring JHH in overlapped regions.

The first publication describes a novel general protocol to generate psNMR spectra by Covariance NMR. This new approach is unique in NMR spectroscopy; giving a cheap, fast an easy way to reconstruct psNMR spectra without spending time in the spectrometer. This new strategy has been referenced to as psNMR Covariance.

The concept of psNMR Covariance has been extended in the second publication by inserting Multiplicity-Edited (ME) information into 2D experiments that are difficult or even impossible to achieve experimentally. It is shown how the ME information can be efficiently transferred to a set of homonuclear and heteronuclear 2D NMR spectra by Covariance processing, reconstructing new psME spectra in a fast way. Finally, G-SERF and related methods only work for isolated 1H signals on which selective excitation can be successfully applied.

Unfortunately, as it happens in other frequency-selective experiments, this approach fails for overlapped signals. A doubly-selective TOCSY G-SERF scheme is presented in the third publication to circumvent this limitation, by measuring JHH efficiently even for protons resonating in crowded regions.

Precise characterization of mycobacterial cell wall lipid PTTM

Molecule confirmation and structure characterization of pentatriacontatrienyl mycolate in Mycobacterium smegmatisby M. Llorens-Fons, E. Julián, M. Luquin and M. Pérez-Trujillo. Chemistry and Physics of Lipids, 2018, Accepted Manuscript. DOI: https://doi.org/10.1016/j.chemphyslip.2017.12.006

Mycobacterium smegmatis is often used to study the different components of mycobacterial cell wall. Mycolic acids are important components of mycobacterial cell wall that have been associated with virulence. Recently, a novel lipid containing mycolic acids has been described in M. smegmatis. However, some uncertainties regarding the structure of this molecule named mycolate ester wax have been reported. The objective of this work was to perform an in depth structural study of this molecule for its precise characterization. Using 1H and 13C NMR spectroscopy, the molecular structure of mycolate ester wax found in M. smegmatis has been elucidated. The characterization was complemented with MS analyses. This molecule is formed by a carbon chain with three methyl substituted olefinic units and a mycolate structure with trans double bonds and cis cyclopropane rings. The present molecular study will facilitate the detection and identification of pentatriacontatrienyl mycolate (PTTM) in future studies by the performance of a simple 1D 1H NMR experiment.