title: Carbon monoxide binding kinetics in "capped" porphyrin compounds.
abstract: The rate constants for CO binding to the five-coordinate ferrous iron complexes of 5,10,15,20-[pyromellitoyl(tetrakis-o-oxyoxyphenyl)]porphyrin and 5,10,15,20-[pyromellitoyl(tetrakis-o-oxypropoxyphenyl)]porphyrin have been measured and compared with the corresponding rate constants for other hemes and hemoproteins. The second-order rate constant is independent of cap size and is comparable to that of high-affinity state hemoglobin (k5 approximately 4 X 10(6) M-1s-1). Therefore, these capped porphyrins provide no steric hindrance to CO binding. In addition, a kinetic scheme involving an unusual seven-coordinate porphyrin species is described.
mesh_terms: D002248:Carbon Monoxide; D055598:Chemical Phenomena; D002621:Chemistry; D006418:Heme; D006420:Hemeproteins; D007501:Iron; D011166:Porphyrins; D013329:Structure-Activity Relationship
chemical_list: D006420:Hemeproteins; D011166:Porphyrins; D006418:Heme; C036220:5,10,15,20-pyromellitoyl(tetrakis(2-oxyethoxyphenyl))porphyrin; C036221:5,10,15,20-pyromellitoyl(tetrakis-(2-oxypropoxyphenyl))porphyrin; D002248:Carbon Monoxide; D007501:Iron