title: Acid-assisted anion interaction with deoxyhemerythrin.
abstract: The interaction of N3-, CNO- and F- with deoxyhemerythrin was monitored from pH 6 to 9 and 3 degrees C to 25 degrees C at an ionic strength 0.5 M (Na2SO4) by using competition with O2. A proton is involved in forming the adduct and is not lost from the protein even at pH values as high as 9. Thermodynamic and kinetic parameters for the interaction of each anion are obtained. It is considered that the proton is introduced as the acid HX and the corresponding parameters for the reaction of HX with deoxyhemerythrin are calculated. These are compared with those for the O2 reaction with deoxyhemerythrin. The adducts are remarkably inert and have dissociation half-lives ranging from 7 s (N3-) to 70 s (CNO- and F-) at 25 degrees C. This stability is ascribed to protonation of a bridged hydroxy group or even bridge-breakage.
mesh_terms: D000143:Acids; D000818:Animals; D000838:Anions / Q000378:metabolism; D003485:Cyanates / Q000378:metabolism; D005459:Fluorides / Q000378:metabolism; D006422:Hemerythrin / Q000031:analogs & derivatives / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008667:Metalloproteins / Q000378:metabolism*; D009570:Nitriles / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D011077:Polychaeta; D013816:Thermodynamics
chemical_list: D000143:Acids; D000838:Anions; D003485:Cyanates; D006422:Hemerythrin; D008667:Metalloproteins; D009570:Nitriles; C043119:deoxyhemerythrin; D005459:Fluorides; D010100:Oxygen