19F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors.
19F Magic Angle Spinning NMR Spectroscopy and Density Functional Theory Calculations of Fluorosubstituted Tryptophans: Integrating Experiment and Theory for Accurate Determination of Chemical Shift Tensors.
J Phys Chem B. 2018 May 14;:
Authors: Lu M, Sarkar S, Wang M, Kraus J, Fritz M, Quinn CM, Bai S, Holmes S, Dybowski C, Yap GPA, Struppe JO, Sergeyev IV, Maas WE, Gronenborn AM, Polenova T
Abstract
The 19F chemical shift is a sensitive NMR probe of structure and electronic environment in organic and biological molecules. In this report we examine chemical shift parameters of 4F-, 5F-, 6F-, and 7F-substituted crystalline tryptophan by magic angle spinning (MAS) solid-state NMR spectroscopy and density functional theory (DFT). Significant narrowing of the 19F lines was observed under fast MAS conditions, at spinning frequencies above 50 kHz. The parameters characterizing the 19F chemical shift tensor are sensitive to the position of the fluorine in the aromatic ring and, to a lesser extent, the chirality of the molecule. Accurate calculations of 19F magnetic shielding tensors require the PBE0 functional with a 50% admixture of a Hartree-Fock exchange term, as well as taking account of the local crystal symmetry. The methodology developed will be beneficial for 19F-based MAS NMR structural analysis of proteins and protein assemblies.
PMID: 29756776 [PubMed - as supplied by publisher]
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