1
|
Rasmussen C, Hoffman DW. Novel Nuclear Magnetic Resonance Method for Position-Specific Carbon Isotope Analysis of Organic Molecules with Significant Impurities. Anal Chem 2022; 94:15124-15131. [PMID: 36265131 DOI: 10.1021/acs.analchem.2c03356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We introduce a novel nuclear magnetic resonance (NMR) tool for determining position-specific carbon (13C/12C) isotope ratios within complex organic molecules. This analytical advancement allows us to measure position-specific isotope ratios of samples that contain impurities with NMR peaks that overlap with the signals of interest. The method involves collecting a series of alternating 13C-coupled and 13C-decoupled 1H NMR spectra using an NMR pulse sequence designed to optimize temperature stability, followed by a data reduction scheme that allows the signals of interest to be isolated from signals of impurities. The method was validated using glycine reference materials with known 13C/12C ratios from the US Geological Survey (USGS) into which impurities typically found in amino acid samples were intentionally introduced. Following validation, the method was used to determine position-specific 13C/12C ratios in a set of USGS l-valine materials (USGS73, -74, -75) that contain significant impurities associated with their biological origin. The l-valines were found to contain distinct intramolecular isotope variability, and the 13Cα isotope spikes in USGS74 and USGS75 were clearly detected, where they preserve carbon isotope ratios of -4.8 ± 0.9‰ and +11.5 ± 0.8‰, respectively. Carbon isotope abundance at the beta and gamma positions indicates that the USGS73 l-valine was obtained from a different source than USGS74 and -75. This analytical approach is a significant step forward in the field of position-specific isotope analysis at natural abundance via NMR because it enables the investigation of samples that contain impurities which are typically present in samples derived from natural sources.
Collapse
Affiliation(s)
- Cornelia Rasmussen
- University of Texas Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 10601 Exploration Way, Austin, Texas78758, United States
| | - David W Hoffman
- Department of Molecular Biosciences, College of Natural Science, University of Texas at Austin, 100 E 24th Street, Austin, Texas78712, United States
| |
Collapse
|
2
|
Rossetto G, Kiraly P, Castañar L, Morris GA, Nilsson M. Improved Quantification by Nuclear Magnetic Resonance Spectroscopy of the Fatty Acid Ester Composition of Extra Virgin Olive Oils. ACS FOOD SCIENCE & TECHNOLOGY 2022; 2:1237-1242. [PMID: 36034339 PMCID: PMC9396653 DOI: 10.1021/acsfoodscitech.2c00057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 06/17/2022] [Accepted: 06/21/2022] [Indexed: 11/30/2022]
Affiliation(s)
- Gabriel Rossetto
- Department of Chemistry, University of Manchester, Oxford Road, ManchesterM13 9PL, UK
| | - Peter Kiraly
- Department of Chemistry, University of Manchester, Oxford Road, ManchesterM13 9PL, UK
| | - Laura Castañar
- Department of Chemistry, University of Manchester, Oxford Road, ManchesterM13 9PL, UK
| | - Gareth A. Morris
- Department of Chemistry, University of Manchester, Oxford Road, ManchesterM13 9PL, UK
| | - Mathias Nilsson
- Department of Chemistry, University of Manchester, Oxford Road, ManchesterM13 9PL, UK
| |
Collapse
|
3
|
Ben-Tal Y, Boaler PJ, Dale HJA, Dooley RE, Fohn NA, Gao Y, García-Domínguez A, Grant KM, Hall AMR, Hayes HLD, Kucharski MM, Wei R, Lloyd-Jones GC. Mechanistic analysis by NMR spectroscopy: A users guide. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2022; 129:28-106. [PMID: 35292133 DOI: 10.1016/j.pnmrs.2022.01.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/05/2022] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
A 'principles and practice' tutorial-style review of the application of solution-phase NMR in the analysis of the mechanisms of homogeneous organic and organometallic reactions and processes. This review of 345 references summarises why solution-phase NMR spectroscopy is uniquely effective in such studies, allowing non-destructive, quantitative analysis of a wide range of nuclei common to organic and organometallic reactions, providing exquisite structural detail, and using instrumentation that is routinely available in most chemistry research facilities. The review is in two parts. The first comprises an introduction to general techniques and equipment, and guidelines for their selection and application. Topics include practical aspects of the reaction itself, reaction monitoring techniques, NMR data acquisition and processing, analysis of temporal concentration data, NMR titrations, DOSY, and the use of isotopes. The second part comprises a series of 15 Case Studies, each selected to illustrate specific techniques and approaches discussed in the first part, including in situ NMR (1/2H, 10/11B, 13C, 15N, 19F, 29Si, 31P), kinetic and equilibrium isotope effects, isotope entrainment, isotope shifts, isotopes at natural abundance, scalar coupling, kinetic analysis (VTNA, RPKA, simulation, steady-state), stopped-flow NMR, flow NMR, rapid injection NMR, pure shift NMR, dynamic nuclear polarisation, 1H/19F DOSY NMR, and in situ illumination NMR.
Collapse
Affiliation(s)
- Yael Ben-Tal
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Patrick J Boaler
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Harvey J A Dale
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Ruth E Dooley
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom; Evotec (UK) Ltd, 114 Innovation Drive, Milton Park, Abingdon, Oxfordshire OX14 4RZ, United Kingdom
| | - Nicole A Fohn
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Yuan Gao
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Andrés García-Domínguez
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Katie M Grant
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Andrew M R Hall
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Hannah L D Hayes
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Maciej M Kucharski
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Ran Wei
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Guy C Lloyd-Jones
- School of Chemistry, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom.
| |
Collapse
|
4
|
Bahadoor A, Brinkmann A, Melanson JE. 13C-Satellite Decoupling Strategies for Improving Accuracy in Quantitative Nuclear Magnetic Resonance. Anal Chem 2021; 93:851-858. [PMID: 33300782 DOI: 10.1021/acs.analchem.0c03428] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Quantitative 1H nuclear magnetic resonance (qHNMR) with an appropriate internal standard is a well-established quantitation method for assigning purity to organic molecules. For accurate measurements, the premise of qHNMR relies on the careful selection of integrals, for both the analyte and the standard, in such a way that the selected integrals are free from interferences. The 13C-satellite signals of adjacent integrals, low-level impurities, and tautomer signals are among the common integral interferences that are typically encountered. One of the simplest ways to identify and avoid these interferences is to decouple the 13C-satellites. Two decoupling schemes were explored to illustrate the benefits of 13C-decoupling for qHNMR or qH{13C}NMR: GARP and bilevel adiabatic broadband decoupling. Unwanted sample heating and nuclear Overhauser effect (NOE) enhancements are the two main drawbacks of decoupling schemes. We show that with careful optimization of acquisition parameters and decoupling power, no excessive sample heating occurred during acquisition at 400 MHz. At 900 MHz, only bilevel adiabatic decoupling could be safely implemented. Furthermore, any undesirable NOE enhancements were completely avoided if acquisition was executed with an inverse-gated pulse sequence. We explored and confirmed the benefits of qH{13C}NMR through the quantitation of a diverse set of compounds, namely, small molecules (dimethyl terephthalate and zearalenone), a 13C-labeled compound (13C6-ochratoxin A), and an octapeptide (angiotensin II). Statistical comparisons confirmed that qH{13C}NMR produced comparable data to qHNMR. However, with qH{13C}NMR data providing added clarity about the presence of overlapping 13C-satellites, impurities, and tautomers, it has an edge over qHNMR for accurate measurements.
Collapse
Affiliation(s)
- Adilah Bahadoor
- Metrology, National Research Council Canada, Ottawa, Ontario K1A 0R6, Canada
| | - Andreas Brinkmann
- Metrology, National Research Council Canada, Ottawa, Ontario K1A 0R6, Canada
| | - Jeremy E Melanson
- Metrology, National Research Council Canada, Ottawa, Ontario K1A 0R6, Canada
| |
Collapse
|
5
|
1H NMR and multi-technique data fusion as metabolomic tool for the classification of golden rums by multivariate statistical analysis. Food Chem 2020; 317:126363. [DOI: 10.1016/j.foodchem.2020.126363] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 01/06/2020] [Accepted: 02/04/2020] [Indexed: 12/12/2022]
|
6
|
González-Fernández D, Torneiro M, Lazzari M. Some Guidelines for the Synthesis and Melting Characterization of Azide Poly(ethylene glycol) Derivatives. Polymers (Basel) 2020; 12:E1269. [PMID: 32498252 PMCID: PMC7362184 DOI: 10.3390/polym12061269] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 05/27/2020] [Accepted: 05/28/2020] [Indexed: 11/25/2022] Open
Abstract
We provide fundamental guidelines in the form of a tutorial to be taken into account for the preparation and characterization of a specific class of poly(ethylene glycol) (PEG) derivatives, namely azide-terminated PEGs. Special attention is given to the effect of these chain end groups and their precursors on properties affecting the PEGylation of proteins, nanoparticles and nanostructured surfaces. Notwithstanding the presence of 13C satellite peaks, we show that 1H NMR enables not only the routine quantitative determination of chain-end substitution, but is also a unique method to calculate the absolute number average molecular weight of PEG derivatives. In the use of size exclusion chromatography to get molecular weight distributions, we highlight the importance of distinguishing between eventual secondary reactions involving molecular weight changes and the formation of PEG complexes due to residual amounts of metal cations from reactants. Finally, we show that azide end groups affect PEG melting behavior. In contrast to oxygen-containing end groups, azides do not interact with PEG segments, thus inducing defect formation in the crystal lattice and the reduction of crystal sizes. Melting temperature and degree of crystallinity decrease become especially relevant for PEGs with very low molecular weight, and its comprehension is particularly important for solid-state applications.
Collapse
Affiliation(s)
- Daniel González-Fernández
- Departamento de Química Física, Facultade de Química, and Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain;
- Departamento de Química Orgánica, Facultade de Química, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - Mercedes Torneiro
- Departamento de Química Orgánica, Facultade de Química, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - Massimo Lazzari
- Departamento de Química Física, Facultade de Química, and Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain;
| |
Collapse
|
7
|
Howe PWA. Is perfection ever attainable? Strong coupling effects in the Perfect Echo. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2020; 58:77-83. [PMID: 31348542 DOI: 10.1002/mrc.4927] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/17/2019] [Accepted: 07/18/2019] [Indexed: 06/10/2023]
Abstract
The Perfect Echo sequence, originally proposed in the late 1980s, has recently been popularised with many applications in the field of small-molecule proton NMR spectroscopy. The Perfect Echo refocuses all homonuclear J-couplings for AX spin systems and refocuses magnetization in-phase for more complex weakly coupled spin systems, albeit with some intensity reduction. In contrast to suggestions in previous publications, spectra acquired in our laboratory showed that the Perfect Echo caused intensity distortions in strongly coupled systems where the chemical shift difference between the coupled spins was not large compared to the J-coupling. This paper reports experimental observations and theoretical analysis of strongly coupled spins to confirm the distortions are real and that they originate principally from transfer of magnetization caused by the final inversion pulse of the Perfect Echo. The intensity changes are not large, but because of them, identifications of coupling partners based on resonance intensities ("roofing") can no longer be relied on when the Perfect Echo is used. However, theory and experiment confirm that adding an orthogonal excitation pulse at the end of the Perfect Echo greatly reduces the distortions.
Collapse
|
8
|
Parella T. Towards perfect NMR: Spin-echo versus perfect-echo building blocks. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2019; 57:13-29. [PMID: 29927497 DOI: 10.1002/mrc.4776] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 06/10/2018] [Accepted: 06/12/2018] [Indexed: 06/08/2023]
Abstract
The development of new tools to improve the quality of nuclear magnetic resonance (NMR) spectra is a challenging task. The concept of "perfect NMR" includes the design of robust pulse sequences that allow an investigator to obtain undistorted pure in-phase signals, with pure absorption lineshapes that are free of phase anomalies derived from undesired J modulations. Here, alternative NMR building blocks to the spin-echo that are based on a general double SE module, known as a perfect-echo, are reviewed. Several implementations to minimize/remove unwanted dispersive contributions in homonuclear and heteronuclear NMR experiments are described and illustrated with some examples of broad interest for small molecules.
Collapse
Affiliation(s)
- Teodor Parella
- Servei de Ressonància Magnètica Nuclear, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| |
Collapse
|
9
|
Moutzouri P, Kiraly P, Foroozandeh M, Phillips AR, Coombes SR, Nilsson M, Morris GA. Suppression of 13C satellites in 1H DOSY spectra. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 295:6-11. [PMID: 30081299 DOI: 10.1016/j.jmr.2018.07.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 07/13/2018] [Accepted: 07/16/2018] [Indexed: 06/08/2023]
Abstract
Diffusion-ordered spectroscopy (DOSY) is a valuable tool for the analysis of intact mixtures, since it can separate the signals of components according to their apparent diffusion coefficients. However, DOSY experiments are acutely sensitive to spectral quality, and especially to signal overlap, which can lead to misleading apparent diffusion coefficients. Here, we introduce a new NMR experiment to reduce signal overlap in mixtures with a wide range of concentrations, by removing one-bond 13C satellites. In such high dynamic range mixtures, 13C isotopomer signals from major components can overlap with signals from minor components, causing problematic distortions in the diffusion domain of a DOSY spectrum. The new method, Oneshot-iDISPEL, is a combination of the Oneshot and DISPEL experiments, and its performance has been demonstrated on a Greek alcoholic beverage, ouzo, which contains small amounts of anise flavour components and sucrose. Ethanol is a major component, and the suppression of its 13C satellites reduces signal overlap with minor components, offering significant improvement in DOSY spectra.
Collapse
Affiliation(s)
- Pinelopi Moutzouri
- School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
| | - Peter Kiraly
- School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | | | - Andrew R Phillips
- Early Product Development, Pharmaceutical Sciences, IMED Biotech Unit, AstraZeneca, Macclesfield SK10 2NA, UK
| | - Steven R Coombes
- Pharmaceutical Technology and Development, AstraZeneca, Silk Road Business Park, Macclesfield SK10 2NA, UK
| | - Mathias Nilsson
- School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Gareth A Morris
- School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| |
Collapse
|
10
|
Howe PWA. Suppression of Protonated Organic Solvents in NMR Spectroscopy Using a Perfect Echo Low-Pass Filtration Pulse Sequence. Anal Chem 2018; 90:4316-4319. [PMID: 29553722 DOI: 10.1021/acs.analchem.8b00621] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Proton NMR spectra are usually acquired using deuterated solvents, but in many cases it is necessary to obtain spectra on samples in protonated solvents. In these cases, the intense resonances of the protonated solvents need to be suppressed to maximize sensitivity and spectral quality. A wide range of highly effective solvent suppression methods have been developed, but additional measures are needed to suppress the 13C satellites of the solvent. Because the satellites represent 1.1% of the original solvent signal, they remain problematic if unsuppressed. The recently proposed DISPEL pulse sequences suppress 13C satellites extremely effectively, and this Technical Note demonstrates that combining DISPEL and presaturation results in exceptionally effective solvent suppression. An important element in the effectiveness is volume selection, which is inherent within the DISPEL sequence. Spectra acquired in protonated dimethlysulfoxide and tetrahydrofuran show that optimum results are obtained by modifying the phase cycle, cycling the pulse-field gradients, and using broadband 13C inversion pulses to reduce the effects of radiofrequency offset and inhomogeneity.
Collapse
Affiliation(s)
- Peter W A Howe
- Syngenta , Jealott's Hill Research Centre , Bracknell , Berkshire , RG42 6EY , U.K
| |
Collapse
|