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Abstract 19F NMR spectroscopy is an attractive and growing area of research with broad applications in biochemistry, chemical biology, medicinal chemistry, and materials science. We have explored fast magic angle spinning (MAS)19F solid‐state NMR spectroscopy in assemblies of HIV‐1 capsid protein. Tryptophan residues with fluorine substitution at the 5‐position of the indole ring were used as the reporters. The19F chemical shifts for the five tryptophan residues are distinct, reflecting differences in their local environment. Spin‐diffusion and radio‐frequency‐driven‐recoupling experiments were performed at MAS frequencies of 35 kHz and 40–60 kHz, respectively. Fast MAS frequencies of 40–60 kHz are essential for consistently establishing19F–19F correlations, yielding interatomic distances of the order of 20 Å. Our results demonstrate the potential of fast MAS19F NMR spectroscopy for structural analysis in large biological assemblies.
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Computational protocol for predicting 19F NMR chemical shifts for PFAS and connection to PFAS structure
Abstract Per‐ and polyfluoroalkyl substances (PFAS) are robust “forever” chemicals that have become global environmental contaminants due to their inability to degrade using traditional techniques. In addition to the persistent nature of PFAS, the structural and functional diversity in PFAS creates a unique challenge in identification and remediation. Their identification is further complicated by the absence of standards for many PFAS. This work is aimed at developing a protocol for computing and establishing accurate19F NMR chemical shifts for PFAS using density functional theory (DFT), which can aid in the identification of PFAS. The impact of solvation and basis sets was evaluated by comparing the computed data with the experimental measurements. Results showed the addition of dispersion corrections in the methodology improve the accuracy of calculated NMR parameters within 4 ppm of the experimental values. Adding a second diffuse function and additional polarization did not improve the accuracy, likely because of the electronegativity of fluorine which does not allow the electron density of fluorine atoms to be polarized. The inclusion of various implicit solvation (DMSO, chloroform, and water) yielded negligible differences in accuracy, and were overall less accurate than the gas phase calculations. The most accurate methodology was then applied to more environmentally relevant PFAS, and the impact of helical nature on the NMR signatures was evaluated. The implication of this work is to be able to improve the identification of structurally diverse PFAS using the19F NMR.
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- PAR ID:
- 10445223
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Computational Chemistry
- Volume:
- 43
- Issue:
- 20
- ISSN:
- 0192-8651
- Page Range / eLocation ID:
- p. 1355-1361
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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