Site-specific resolution of anionic residues in proteins using solid-state NMR spectroscopy

Jianping Li, Ampon Sae Her, Nathaniel J. Traaseth

Research output: Contribution to journalArticlepeer-review


NMR spectroscopy is commonly used to infer site-specific acid dissociation constants (pKa) since the chemical shift is sensitive to the protonation state. Methods that probe atoms nearest to the functional groups involved in acid/base chemistry are the most sensitive for determining the protonation state. In this work, we describe a magic-angle-spinning (MAS) solid-state NMR approach to measure chemical shifts on the side chain of the anionic residues aspartate and glutamate. This method involves a combination of double quantum spectroscopy in the indirect dimension and REDOR dephasing to provide a sensitive and resolved view of these amino acid residues that are commonly involved in enzyme catalysis and membrane protein transport. To demonstrate the applicability of the approach, we carried out measurements using a microcrystalline soluble protein (ubiquitin) and a membrane protein embedded in lipid bilayers (EmrE). Overall, the resolution available from the double quantum dimension and confidence in identification of aspartate and glutamate residues from the REDOR filter make this method the most convenient for characterizing protonation states and deriving pKa values using MAS solid-state NMR.

Original languageEnglish (US)
Pages (from-to)355-363
Number of pages9
JournalJournal of Biomolecular NMR
Issue number6-7
StatePublished - Jul 1 2020


  • Acid dissociation constants
  • EmrE
  • Magic-angle-spinning
  • Membrane proteins
  • Microcrystalline proteins
  • Solid-state NMR

ASJC Scopus subject areas

  • Biochemistry
  • Spectroscopy


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