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Hartman JD, Spock LE, Harper JK. Benchmark accuracy of predicted NMR observables for quadrupolar 14 N and 17 O nuclei in molecular crystals. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2023; 61:253-267. [PMID: 36567433 DOI: 10.1002/mrc.5328] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 12/21/2022] [Accepted: 12/22/2022] [Indexed: 06/17/2023]
Abstract
Nuclear quadrupole resonances for 14 N and 17 O nuclei are exquisitely sensitive to interactions with surrounding atoms. As a result, nitrogen and oxygen solid-state nuclear magnetic resonance (ssNMR) provides a powerful tool for investigating structure and dynamics in complex systems. First-principles calculations are increasingly used to facilitate spectral assignment and to evaluate and adjust crystal structures. Recent work combining the strengths of planewave density functional theory (DFT) calculations with a single molecule correction obtained using a higher level of theory has proven successful in improving the accuracy of predicted chemical shielding (CS) tensors and 17 O quadrupolar coupling constants ( C q ). Here we extend this work by examining the accuracy of predicted 14 N and 17 O electric field gradient (EFG) tensor components obtained using alternative planewave-corrections involving cluster and two-body fragment-based calculations. We benchmark the accuracy of CS and EFG tensor predictions for both nitrogen and oxygen using planewave, two-body fragment, and enhanced planewave-corrected techniques. Combining planewave and two-body fragment calculations reduces the error in predicted 17 O C q values by 35% relative to traditional planewave calculations. These enhanced planewave-correction methods improve the accuracy of 17 O and 14 N EFG tensor components by 15% relative to planewave DFT but yield minimal improvement relative to a simple molecular correction. However, in structural environments involving either high symmetry or strong intermolecular interactions, enhanced planewave-corrected methods provide a distinct advantage.
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Affiliation(s)
- Joshua D Hartman
- Department of Chemistry, University of California, Riverside, Riverside, California, USA
| | - Lilian E Spock
- Department of Chemistry, University of California, Riverside, Riverside, California, USA
| | - James K Harper
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah, USA
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Špačková J, Goldberga I, Yadav R, Cazals G, Lebrun A, Verdié P, Métro TX, Laurencin D. Fast and Cost-Efficient 17 O-Isotopic Labeling of Carboxylic Groups in Biomolecules: From Free Amino Acids to Peptide Chains. Chemistry 2023; 29:e202203014. [PMID: 36333272 DOI: 10.1002/chem.202203014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 11/04/2022] [Indexed: 11/08/2022]
Abstract
17 O NMR spectroscopy is a powerful technique, which can provide unique information regarding the structure and reactivity of biomolecules. However, the low natural abundance of 17 O (0.04 %) generally requires working with enriched samples, which are not easily accessible. Here, we present simple, fast and cost-efficient 17 O-enrichment strategies for amino acids and peptides by using mechanochemistry. First, five unprotected amino acids were enriched under ambient conditions, consuming only microliter amounts of costly labeled water, and producing pure molecules with enrichment levels up to ∼40 %, yields ∼60-85 %, and no loss of optical purity. Subsequently, 17 O-enriched Fmoc/tBu-protected amino acids were produced on a 1 g/day scale with high enrichment levels. Lastly, a site-selective 17 O-labeling of carboxylic functions in peptide side-chains was achieved for RGD and GRGDS peptides, with ∼28 % enrichment level. For all molecules, 17 O ssNMR spectra were recorded at 14.1 T in reasonable times, making this an important step forward for future NMR studies of biomolecules.
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Affiliation(s)
| | | | - Rishit Yadav
- ICGM, CNRS, UM, ENSCM, 34293, Montpellier, France
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Ha M, Nader S, Pawsey S, Struppe J, Monette M, Mansy SS, Boekhoven J, Michaelis VK. Racing toward Fast and Effective 17O Isotopic Labeling and Nuclear Magnetic Resonance Spectroscopy of N-Formyl-MLF-OH and Associated Building Blocks. J Phys Chem B 2021; 125:11916-11926. [PMID: 34694819 DOI: 10.1021/acs.jpcb.1c07397] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Solid-state 1H, 13C, and 15N nuclear magnetic resonance (NMR) spectroscopy has been an essential analytical method in studying complex molecules and biomolecules for decades. While oxygen-17 (17O) NMR is an ideal and robust candidate to study hydrogen bonding within secondary and tertiary protein structures for example, it continues to elude many. We discuss an improved multiple-turnover labeling procedure to develop a fast and cost-effective method to 17O label fluoroenylmethyloxycarbonyl (Fmoc)-protected amino acid building blocks. This approach allows for inexpensive ($0.25 USD/mg) insertion of 17O labels, an important barrier to overcome for future biomolecular studies. The 17O NMR results of these building blocks and a site-specific strategy for labeled N-acetyl-MLF-OH and N-formyl-MLF-OH tripeptides are presented. We showcase growth in NMR development for maximizing sensitivity gains using emerging sensitivity enhancement techniques including population transfer, high-field dynamic nuclear polarization, and cross-polarization magic-angle spinning cryoprobes.
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Affiliation(s)
- Michelle Ha
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Serge Nader
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Shane Pawsey
- Bruker Biospin Corporation, 15 Fortune Drive, Billerica, Massachusetts 01821, United States
| | - Jochem Struppe
- Bruker Biospin Corporation, 15 Fortune Drive, Billerica, Massachusetts 01821, United States
| | - Martine Monette
- Bruker BioSpin Ltd., Bruker Corporation, 555 Steeles Avenue E, Milton, Ontario L9T 1Y6, Canada
| | - Sheref S Mansy
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Job Boekhoven
- Department of Chemistry, Technical University of Munich, Lichtenbergstraße 4, Garching 85748, Germany.,Institute for Advanced Study, Technical University of Munich, Lichtenbergstraße 2a, Garching 85748, Germany
| | - Vladimir K Michaelis
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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