Protonation of type-1 Cu bound histidines: a quantum chemical study.

摘要: The protonation of the solvent-exposed histidine ligands type-1 Cu sites in five proteins, Thiobacillus ferrooxidans rusticyanin, Pseudomonas aeruginosa azurin, fern plastocyanin, Alcaligenes faecalis pseudoazurin, and Paracoccus versutus amicyanin, were studied with quantum chemical methods conductorlike polarizable continuum model (CPCM). Active site molecules consisting approximately 140 atoms extracted from X-ray crystal structures optimized homogeneous CPCM/B3LYP/6-31G* method some fixed. More accurate solvation effects obtained using a recently developed heterogeneous CPCM to describe protein matrix aqueous molecules. In different effective dielectric constants, 4, 10, 78.39, used for portions surfaces encapsulating active It is found that two conformations protonated histidine, imidazolium unflipped flipped, show similar energies these proteins. calculated pK(a) values are comparable experimental values. According calculations, main determinants local interactions contained effects, as well polarization.