title: Differentiation of histidine tautomeric states using (15)N selectively filtered (13)C solid-state NMR spectroscopy.
abstract: The histidine imidazole ring in proteins usually contains a mixture of three possible tautomeric states (two neutral - τ and π states and a charged state) at physiological pHs. Differentiating the tautomeric states is critical for understanding how the histidine residue participates in many structurally and functionally important proteins. In this work, one dimensional (15)N selectively filtered (13)C solid-state NMR spectroscopy is proposed to differentiate histidine tautomeric states and to identify all (13)C resonances of the individual imidazole rings in a mixture of tautomeric states. When (15)N selective 180° pulses are applied to the protonated or non-protonated nitrogen region, the (13)C sites that are bonded to the non-protonated or protonated nitrogen sites can be identified, respectively. A sample of (13)C, (15)N labeled histidine powder lyophilized from a solution at pH 6.3 has been used to illustrate the usefulness of this scheme by uniquely assigning resonances of the neutral τ and charged states from the mixture.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Yimin
authors.initials: Y
authors.lastname: Miao
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA; National High Magnet Field Lab, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA.
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Cross
authors.affiliation: National High Magnet Field Lab, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA. Electronic address: rfu@magnet.fsu.edu.
authors.forename: Riqiang
authors.initials: R
authors.lastname: Fu
mesh_terms: D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods*; D006639:Histidine / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry*; D009587:Nitrogen Isotopes; D011506:Proteins / Q000737:chemistry
chemical_list: D007093:Imidazoles; D009587:Nitrogen Isotopes; D011506:Proteins; D006639:Histidine
keywords: Histidine tautomeric states; REDOR/TEDOR; Selective polarization; Solid-state MAS NMR