Differentiation of histidine tautomeric states using super(15)N selectively filtered super(13)C solid-state NMR spectroscopy

• Published in: Journal of magnetic resonance (1997) Vol. 245; pp. 105 - 109
• Main Authors: Miao, Yimin, Cross, Timothy A, Fu, Riqiang
• Format: Journal Article
• Language: English
• Published: 01-08-2014
• Subjects: Bonding; Charging; Differentiation; Histidine; Imidazole; NMR spectroscopy; Proteins; Residues
• ISSN: 1090-7807
• DOI: 10.1016/j.jmr.2014.06.005

The histidine imidazole ring in proteins usually contains a mixture of three possible tautomeric states (two neutral - tau and pi 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 super(15)N selectively filtered super(13)C solid-state NMR spectroscopy is proposed to differentiate histidine tautomeric states and to identify all super(13)C resonances of the individual imidazole rings in a mixture of tautomeric states. When super(15)N selective 180 degree pulses are applied to the protonated or non-protonated nitrogen region, the super(13)C sites that are bonded to the non-protonated or protonated nitrogen sites can be identified, respectively. A sample of super(13)C, super(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 tau and charged states from the mixture.