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).

Ex vivo method to evaluate MRI contrast agents

2014-10-13Methods & Applications, News from the SeRMN, Our Publicationsanimal-model, biospec, contrast-agents, MRISilvia

“A new ex vivo method to evaluate the performance of candidate MRI contrast agents: a proof-of-concept study” by Candiota A.P., Acosta M., Simões R.V., Delgado-Goñi T., Lope-Piedrafita S., Irure A., Marradi M., Bomatí-Miguel O., Miguel-Sancho N., Abasolo I., Schwartz S. Jr., Santamaría J., Penadés S., Arús C. J Nanobiotechnology 2014 12:12. DOI: 10.1186/1477-3155-12-12.

A new method has been developed for selecting MRI contrast agents with better expected in vivo performance. This method requires only a very small amount of contrast agent (e.g. 5 nmols/animal, 800 times less than the quantity necessary for in vivo administration) and allows to carry out a more rationally informed candidate selection, avoiding unnecessary in vivo and toxicology tests for the ex vivo poorly performing substances, consequently reducing animal needs, material consumption and overall costs. Continue reading Ex vivo method to evaluate MRI contrast agents →

Diversity of pyrrolizidine alkaloids in native and invasive Senecio pterophorus (Asteraceae): Implications for toxicity

2014-10-06Methods & Applications, Our Publications, Our Researchalkaloids, ecology, phytochemistry, toxicityMiriam

“Diversity of pyrrolizidine alkaloids in native and invasive Senecio pterophorus (Asteraceae): Implications for toxicity” by Eva Castells, Patrick P.J. Mulder and Miriam Perez-Trujillo. Phytochemistry (2014) 108:137-146. DOI: 10.1016/j.phytochem.2014.09.006

Changes in plant chemical defenses after invasion could have consequences on the invaded ecosystems by modifying the interactions between plants and herbivores and facilitating invasion success. However, no comprehensive biogeographical studies have yet determined the phenotypic levels of plant chemical defenses, as consumed by local herbivores, covering large distributional areas of a species. Continue reading Diversity of pyrrolizidine alkaloids in native and invasive Senecio pterophorus (Asteraceae): Implications for toxicity →

Perfect-HSQC experiments: pure in-phase spectra

2014-10-04Methods & Applications, Our Publications, Our Researchheteronulear coupling constants, HSQC, one-bond proton-carbon coupling constants, perfect HSQC, proton-proton coupling constants, pure in-phase signalsLaura

“Suppresión of phase and amplitude J_HH modulations in HSQC experiments” by Laura Castañar, Eduard Sistaré, Albert Virgili, Robert Thomas Williamson and Teodor Parella. Magnetic Resonance in Chemistry, 2014 , 53:115-119. DOI: 10.1002/mrc.4149

The amplitude and the phase of cross peaks in conventional 2D HSQC experiments are modulated by both proton–proton, J_HH, and proton–carbon, ¹J_CH, coupling constants. It is shown by spectral simulation and experimentally that J_HH interferences are suppressed in a novel perfect-HSQC pulse scheme that incorporates perfect-echo INEPT periods. Continue reading Perfect-HSQC experiments: pure in-phase spectra →

SeRMN presentations at the 2014 Ibero-American NMR & GERMN Bienal & Iberian NMR meeting

2014-09-15Methods & Applications, NMR Events & Courses, Our Researchchirality, enantiodifferentiation, enhanced resolution, full sensitivity, HOBS, HOBS-TOCSY, homodecoupling, homonuclear decoupling, multipl, pure-shift NMRLaura

Some of our last research work will be presented next week at the VI Ibero-American NMR – VII GERMN Bienal – IV Iberian NMR joint meeting that will take place in Alcalá de Henares, Madrid (Spain) from 22^nd to 25^th September. Find below a summary of our contributions.

Laura Castañar presents an oral communication and a poster entitled “Enantiodifferentiation throgh frequency-selective pure shift ¹H NMR”. NMR-aided discrimination of enantiomers using chiral solvating agents (CSAs) is a well established method to carry out enantiodifferentiation studies. Continue reading SeRMN presentations at the 2014 Ibero-American NMR & GERMN Bienal & Iberian NMR meeting →

Simultaneous 1H and 13C NMR enantiodifferentiation from highly-resolved pure shift HSQC spectra

2014-07-17Methods & Applications, Our Publications, Our Researchchirality, enantiodifferentiation, enhanced resolution, homodecoupling, homonuclear decoupling, HSQC, pure-shift NMR, spectral aliasingMiriam

“Simultaneous ¹H and ¹³C NMR enantiodifferentiation from highly-resolved pure shift HSQC spectra” by Miriam Pérez-Trujillo, Laura Castañar, Eva Monteagudo, Lars T. Kuhn, Pau Nolis, Albert Virgili, R. Thomas Williamson and Teodor Parella. Chemical Communications 50:10214-10217 (2014). DOI: 10.1039/C4CC04077E

NMR-aided discrimination of enantiomers using chiral solvating agents (CSAs) is a well established method of enantiodifferentiation and measurement of enantiomeric ratios (er). The analysis is traditionally performed by observing chemical shift differences (ΔΔδ) in ¹H signals by conventional 1D ¹H NMR spectra. However, low ΔΔδ values and signal overlap caused by complex multiplets lead to the lack of spectral signal dispersion that preclude a straightforward analysis. Continue reading Simultaneous 1H and 13C NMR enantiodifferentiation from highly-resolved pure shift HSQC spectra →

Pure In-Phase Heteronuclear Correlation NMR Experiments

2014-06-27Methods & Applications, Our Publications, Our Researchheteronulear coupling constants, HSQC, HSQMBC, IPAP, PIP experiments, proton-carbon coupling constants, proton-proton coupling constantsLaura

“Pure In-Phase Heteronuclear Correlation NMR Experiments ” by Laura Castañar, Josep Sauri, Robert Thomas Williamson, Albert Virgili and Teodor Parella. Angew. Chem. Int. Ed. 2014, 53, 8379-8382. DOI: 10.1002/anie.201404136

A general NMR approach to provide pure in-phase (PIP) multiplets in heteronuclear correlation experiments is described. The implementation of a z-filter efficiently suppresses any unwanted anti-phase contributions that usually distort the multiplet pattern of cross-peaks and can make their analysis difficult. Continue reading Pure In-Phase Heteronuclear Correlation NMR Experiments →

PhD Thesis: Modern NMR Methodologies for the Measurement of Homo- and Heteronuclear Coupling Constants in Small Molecules

2014-05-29Methods & Applications, News from the SeRMN, Our ResearchE.COSY, HSQMBC, IPAP, J-resolved, PhD Thesis, proton-carbon coupling constants, spin-state selectionJosep

Last 21^st May 2014 I defended my PhD Thesis entitled: Modern NMR Methodologies for the Measurement of Homo- and Heteronuclear Coupling Constants in Small Molecules

The dissertation is focused on the development of modern NMR methodologies for the measurement of homo- and heteronuclear coupling constants in small molecules, and is presented as a compendium of eight (8) publications that have been published in several peer-reviewed journals as original research papers. Continue reading PhD Thesis: Modern NMR Methodologies for the Measurement of Homo- and Heteronuclear Coupling Constants in Small Molecules →

HOBS experiments to measure T₁/T₂ relaxation times in overlapped regions

2014-05-14Methods & Applications, Our Publications, Our Research, Uncategorizedband-selective, CPMG, enhanced resolution, full sensitivity, HOBS, homodecoupling, homonuclear decoupling, Inversion Recovery, PROJECT, pure-shift NMR, Relaxation times, T1-relaxation, T2-relaxationLaura

“Measurement of T₁/T₂ relaxation times in overlapped regions from homodecoupled ¹H singlet signals” by Laura Castañar, Pau Nolis, Albert Virgili and Teodor Parella. Journal of Magnetic Resonance 244 (2014) 30-35. DOI: 10.1016/j.jmr.2014.04.003

The implementation of the HOmodecoupled Band-Selective (HOBS) technique in the conventional Inversion-Recovery and CPMG-based PROJECT experiments is described. The achievement of fully homodecoupled signals allows the distinction of overlapped ¹H resonances with small chemical shift differences. It is shown that the corresponding T₁ and T₂ relaxation times can be individually measured from the resulting singlet lines using conventional exponential curve-fitting methods. Continue reading HOBS experiments to measure T₁/T₂ relaxation times in overlapped regions →

HOBS Applications

2014-03-26Methods & Applications, Our Research, Seminarsenantiodifferentiation, enhanced resolution, full sensitivity, HOBS, HOBS-HSQC, HOBS-HSQMBC, HOBS-TOCSY, homodecoupling, homonuclear decoupling, proton-carbon coupling constants, pure-shift NMRLaura

SeRMN seminar

Date: Friday 28th March, 2014
Hour: 12 am
Location: SeRMN, Facultats de Ciències i Biociències, C2/-135
Speaker: Laura Castañar, SeRMN PhD Student & Teaching Assistant, Dept. of Chemistry.

Several NMR applications using HOmodecouped Band-Selective NMR experiments [1] are proposed. The easy implementation of this HOBS scheme as a general building block into a great variety of multidimensional NMR experiments leads to pure-shift spectra with enhanced resolution and with the maximum attainable sensitivity. In this talk is presented the application of HOBS for measuring direct [1] and long-range [2] heteronuclear coupling constants. Also the use of HOBS experiments to enantiodiscrimination studies are presented [3].

Reference:

[1] “Full sensitivity and enhanced resolution in homodecoupled band-selective NMR experiments” by L. Castañar, P. Nolis, A. Virgili and T. Parella. Chem. Eur. J. 2013, 19, 17283-17286. DOI: 10.1002/chem.201303235

[2] “Implementing homo- and heterodecoupling in region-selective HSQMBC experiments” by Laura Castañar, Josep Sauri, Pau Nolis,Albert Virgili and Teodor Parella. Journal of Magnetic Resonance,2014, 238, 63-69. DOI:10.1016/j.jmr.2013.10.022

[3] “Enantiodifferentiation through Frequency-Selective Pure-Shift 1H Nuclear Magnetic Resonance Spectroscopy” by Laura Castañar, Míriam Pérez-Trujillo, Pau Nolis, Eva Monteagudo , Albert Virgili and Teodor Parella. ChemPhysChem, 2014. DOI: 10.1002/cphc.201301130

Continue reading HOBS Applications →

Rapid and efficient enantiodifferentiation through frequency-selective pure-shift ¹H NMR spectroscopy

2014-03-06Methods & Applications, Our Publications, Our Researchband-selective, enantiodifferentiation, enhanced resolution, full sensitivity, HOBS, homodecoupling, homonuclear decoupling, pure-shift NMRLaura

“Enantiodifferentiation through Frequency-Selective Pure-Shift ¹H Nuclear Magnetic Resonance Spectroscopy” by Laura Castañar, Míriam Pérez-Trujillo, Pau Nolis, Eva Monteagudo , Albert Virgili and Teodor Parella. ChemPhysChem,15 (2014) 854-857.

DOI: 10.1002/cphc.201301130

A frequency-selective 1D ¹H NMR experiment for the fast and sensitive determination of chemical shift differences between overlapped resonances is proposed. The resulting fully homodecoupled ¹H resonances appear as resolved 1D singlets without their typical J_HH multiplet structure. The achieved high signal dispersion is here exploited in enantiodiscrimination studies using chiral solvating agents. Continue reading Rapid and efficient enantiodifferentiation through frequency-selective pure-shift ¹H NMR spectroscopy →

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