title: Effects of synergistic anions on the proton magnetic resonance spectra and pH titration of histidinyl side chains in the C-terminal half-molecule of ovotransferrin.
abstract: High-resolution proton magnetic resonance spectra of the C-terminal half-molecule of ovotransferrin (OTf/2C) clearly resolve the C(2)H resonances of the five histidinyl residues in the protein. Formation of the Ga(III)OTf/2C(anion) ternary complexes results in different chemical shift and titration behaviors for certain C(2)H resonances in the carbonato, oxalato, and malonato complexes. The pKa' of the imidazole group involved in a proton relay with the synergistic anion and a water of hydration appears to be anion independent. Thus the initial attack of a proton on the ternary complex appears to be at a ligand other than the anion or anion-binding imidazole group.
mesh_terms: D000838:Anions; D003207:Conalbumin / Q000378:metabolism*; D004357:Drug Synergism; D004527:Egg Proteins / Q000378:metabolism*; D006639:Histidine; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D011522:Protons; D014357:Trypsin
chemical_list: D000838:Anions; D004527:Egg Proteins; D011522:Protons; D003207:Conalbumin; D006639:Histidine; D014357:Trypsin