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PhD Thesis: Advances in NMR spectroscopic methodology and applications: time-efficient methods, ultra long-range heteronuclear correlation experiments and enantiospecific analysis of complex mixtures.

Methods & Applications, News from the SeRMN, Our Research

Last 21st October 2021 I defended my PhD Thesis entitled: Advances in NMR spectroscopic methodology and applications: time-efficient methods, ultra long-range heteronuclear correlation experiments and enantiospecific analysis of complex mixtures.

The thesis is divided into the following topics:

  • the development of Nuclear Magnetic Resonance (NMR) experiments focused on efficiency in terms of time;
  • establishing new pulse sequences that facilitate the study of long-distance coupling constants fundamental for structural elucidation;
  • the development of a reliable method that allows the differentiated analysis of enantiomers (enantiospecific) directly from its original mixture (in situ) and from multiple molecules simultaneously (multicomponent).

The NMR experiments developed using the MFA (Multiple Fid Acquisition) approach based on the “afterglow magnetization”, allows a considerable reduction of the experimental time by acquiring several experiments at the same time, which are stored in different FIDs that can be visualized separately. In this thesis several works are presented that allow to make a structural elucidation of organic molecules in a fast, simple and unambiguous way, among them MFA-COSY / RELAY3, MFA-COSY / TOCSY, MFA-HMBC / HMBC-COSY, MFA-MBOB -COSY, MFA-TOCSY / TOCSY, MFA-HSQC / HSQC and the MFA-HSQC / Pure-shiftHSQC. Furthermore, with an adequate combination of MFA and “Spectral Aliasing” (SA), a new experiment is presented, which in addition to the experimental time improves spectral resolution and facilitates structural identification. The SA, despite being a powerful experiment to avoid signal overlapping has an important disadvantage related to the identification of each signal, to avoid this problem, for a few extra seconds, we acquired the two heteronuclear experiments in 2D, the HSQC with “Spectral Aliasing” and the standard HSQC to facilitate signal assignment.

Furthermore, in terms of improving the spectral resolution, this thesis presents two experiments following the Pure-shift methodology to eliminate the proton-proton coupling constant, using BIRD (BIlinear Rotation Decoupling) to perform heteronuclear decoupling, minimizing signal overlapping. The novelty of this work is based on the detection of multiple nuclei in the same 2D spectrum, nitrogen and carbon in the indirect dimension (F1) and proton in F2, is what is known as “Time-Shared NMR experiments”. In addition, using the same approach, a second experiment is presented that allows the calculation (via direct observation) of the heteronuclear proton-carbon and proton-nitrogen coupling constants simultaneously. The measurement of long-distance heteronuclear coupling constants remains a challenge in NMR spectroscopy, due to their tiny values and to the difficulty of their measurement. A modification in the LR-HSQMBC (changing some 180º pulses of the experiment by selective pulses irradiated in an area of the spectrum) allows the measurement of very small coupling constants (of up to 6 separation bonds). In this work, the advantages of the new LR-selHSQMBC NMR experiment are exposed and the advantages and disadvantages of both experiments are compared.

Finally, this thesis presents an innovative work related to the enantiospecific and simultaneous detection of multiple pairs of enantiomers in a mixture without prior separation or derivatization of the sample components and with minimal sample manipulation. This method is based on NMR spectroscopy and on the use of a chiral solvating agent (CSA) as chiral auxiliary. This work shows, as a proof of concept, the simultaneous enantiospecific detection of multiple enantiomeric pairs directly within the original mixture. This is demonstrated with an aqueous mixture of the essential amino acids in their D and L forms.

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

ACKNOWLEDGMENTS

I would like to thank the financial support for this research by Spanish MINECO projects “Diseño y Aplicación de Nuevas Metodologías en Resonancia Magnética Nuclear” (CTQ2015-64436-P) and “Metodologías Modernas en Resonancia Magnética Nuclear de Moleculas Pequeñas” (PGC2018-095808-B-I00) and for the grant BES-2016-078903 awarded by Agencia Estatal de Investigación.

SeRMN contribution at SMASH 2019

Methods & Applications, NMR Events & Courses, Our Research

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. 
poster_MFA_Download

Kumar Motiram-Corral, PhD student at SeRMN, participates in the “Novena Edició de les Jornades Doctorals” by Dept. of Chemistry, UAB.

News from the SeRMN, Our Research

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).

New time-efficient approach in TOCSY and HSQC experiments

Our Publications, Our Research

Nolis, Pau, Kumar Motiram‐Corral, Míriam Pérez‐Trujillo & Teodor Parella. 2018. Interleaved Dual NMR Acquisition of Equivalent Transfer Pathways in TOCSY and HSQC Experiments. ChemPhysChem 20(3). 356–360. DOI: 10.1002/cphc.201801034

A dual NMR data acquisition strategy to handle and detect two active equivalent transfer pathways is presented and discussed. We illustrate the power of this time-efficient approach by collecting two different 2D spectra simultaneously in a single experiment: (i) TOCSY or HSQC-TOCSY spectra with different mixing times, (ii) F2-13C-coupled and decoupled HSQC spectra, (iii) conventional and pureshift HSQC spectra, and (iv) complementary HSQC and HSQC-TOCSY spectra.

MFA-Tocsy-TocsyDownload
MFA-HSQC-HSQCDownload

Saving time using different NMR concepts

Our Publications, Our Research

Nolis, Pau, Kumar Motiram-Corral, Míriam Pérez-Trujillo & Teodor Parella. 2019. Broadband homodecoupled time-shared 1H-13C and 1H-15N HSQC experiments. Journal of Magnetic Resonance 298. 23–30. DOI: 10.1016/j.jmr.2018.11.00

The concepts of pure-shift NMR and time-shared NMR are merged in a single NMR experiment. A 13C/15N time-shared version of the real-time BIRD-based broadband homodecoupled HSQC experiment is described. This time-efficient approach affords simultaneously 1H-13C and 1H-15N pure-shift HSQC spectra in a single acquisition, while achieving substantial gains in both sensitivity and spectral resolution. We also present a related 13C/15N-F2-coupled homodecoupled version of the CLIP-HSQC experiment for the simultaneous measurement of 1JCH and 1JNH from the simplified doublets observed along the direct dimension. Finally, a novel J-resolved HSQC experiment has been designed for the simple and automated determination of both 1JCH/1JNH from a 2D J-resolved spectrum.

4 experiments in 1 shot

Our Publications, Our Research

Motiram-Corral, Kumar, Míriam Pérez-Trujillo, Pau Nolis & Teodor Parella. 2018. Implementing one-shot multiple-FID acquisition into homonuclear and heteronuclear NMR experiments. Chemical Communications 54(96). 13507–13510. DOI: 10.1039/c8cc08065h

Multiple-FID acquisition (MFA) within the same scan is applied to acquire simultaneously multiple 2D spectra from a single NMR experiment. A discussion on the incorporation of the MFA strategy in several homonuclear and heteronuclear 2D pulse sequences is presented. As a proof of concept, a set of novel COSY, TOCSY and HMBC experiments are reported as a time-efficient solution in small-molecule NMR spectroscopy.

Continue reading 4 experiments in 1 shot →