Poster Presentation 23rd International Society of Magnetic Resonance Conference 2023

Scalar through-space 19F-19F couplings in proteins (#201)

Gottfried Otting 1 , Elwy Abdelkader 1 , Henry Orton 1 , Iresha Herath 1 , Ansis Maleckis 2
  1. The Australian National University, Canberra, ACT, Australia
  2. Latvian Institute of Organic Synthesis, Riga, Latvia

­­Fluorination of amino acids provides an alternative to labelling proteins with stable isotopes. 19F-NMR spectroscopy is sensitive, and the substitution of a carbon-bonded hydrogen for fluorine presents a remarkably small perturbation, the C-F bond being only 0.3 Å longer than the C-H bond, the van der Waals radius of fluorine being larger by 0.15 Å and C-F groups displaying a high level of hydrophobicity. Different versions of leucine and valine were synthesized where either one or both of the methyl groups contained single fluorine atoms. These amino acids were used in cell-free protein synthesis to produce the small protein GB1, where either all leucine or all valine residues were replaced by the fluorine-labelled analogues (Maleckis et al., 2022). The structure of the protein remained intact as evidenced by conserved 1H-NOESY spectra. 19F-TOCSY spectra revealed scalar through-space 19F-19F couplings between fluorine atoms in different amino acid residues. The detection of 19F-19F contacts is more facile by through-space couplings than by 19F-NOESY, and even transient contacts can be picked up readily (Orton et al., 2021).

  1. Maleckis, A., Abdelkader, E. H., Herath, I. D. and Otting, G. (2022) Synthesis of fluorinated leucines, valines and alanines for use in protein NMR. Org. Biomol. Chem. 20, 2424-2432.
  2. Orton, H. W., Qianzhu, H., Abdelkader, E. H., Tan, Y. J., Habel, E. I., Frkic, R. L., Jackson, C. J., Huber, T. and Otting, G. (2021) Through-space scalar 19F–19F couplings between fluorinated non-canonical amino acids for the detection of specific contacts in proteins. J. Am. Chem. Soc. 143, 19587-19598.