Limiting Values of the one-bond C-H Spin-Spin Coupling Constants of the Imidazole Ring of Histidine at High-pH.

ABSTRACT: Assessment of the relative amounts of the forms of the imidazole ring of Histidine (His), namely the protonated (H⁺) and the tautomeric N^ε2-H and N^δ1-H forms, respectively, is a challenging task in NMR spectroscopy. Indeed, their determination by direct observation of the ¹⁵N and ¹³C chemical shifts or the one-bond C-H, ¹J_CH, Spin-Spin Coupling Constants (SSCC) requires knowledge of the "canonical" limiting values of these forms in which each one is present to the extent of 100%. In particular, at high-pH, an accurate determination of these "canonical" limiting values, at which the tautomeric forms of His coexist, is an elusive problem in NMR spectroscopy. Among different NMR-based approaches to treat this

SUBMITTER: Vila JA 

PROVIDER: S-EPMC5596661 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature