pH-dependence of 13C chemical shifts and 13C,H coupling constants in imidazole and L-histidine.
The pH-dependence of selected 13C chemical shifts reflects the state of ionization of the imidazole ring in both imidazole and L-histidine. Titration of the amino and carboxyl groups of histidine also perturbs the shifts. The coupling constants 1J (13C(2),H) and 1J (13C(5),H) for both compounds also vary with pH, but in L-histidine these constants are relatively insensitive to the titration of groups outside the imidazole ring.
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006639:Histidine; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy
D007093:Imidazoles; D006639:Histidine