Model studies of the histidine-tyrosine cross-link in cytochrome C oxidase reveal the flexible substituent effect of the imidazole moiety.
[reaction: see text] Experimental and theoretical studies were carried out to interrogate the effect of an imidazole substituent in each of the ortho, meta, and para positions on the pK(a), E degrees , and O-H BDE of phenol. The results reveal that imidazole substitution lowers the pK(a) of phenol and increases the E degrees of phenoxide due to its sigma-electron withdrawing ability (sigma(p)(-) = +0.21, sigma(m)(-) = +0.45) but decreases the O-H BDE and E degrees of phenol due to its pi-electron-donating ability (sigma(p)(+) = -0.45).
Pratt
Derek A
DA
Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Pesavento
Russell P
RP
van der Donk
Wilfred A
WA
D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry / Q000493:pharmacokinetics*; D008962:Models, Theoretical; D008968:Molecular Conformation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000737:chemistry
D007093:Imidazoles; D014443:Tyrosine; D006639:Histidine; C029899:imidazole; D003576:Electron Transport Complex IV