1004985-30-1Relevant articles and documents
Heme/copper assembly mediated nitrite and nitric oxide interconversion
Hematian, Shabnam,Siegler, Maxime A.,Karlin, Kenneth D.
, p. 18912 - 18915 (2012)
The hemea3/CuB active site of cytochrome c oxidase is responsible for cellular nitrite reduction to nitric oxide; the same center can return NO to the nitrite pool via oxidative chemistry. Here, we show that a partially reduced heme/Cu assembly reduces NO2- ion, producing nitric oxide. The heme serves as the reductant, but the Cu II ion is also required. In turn, a μ-oxo heme-Fe III-O-CuII complex facilitates NO oxidation to nitrite; the final products are the reduced heme and CuII-nitrito complexes.
Synthesis and characterization of reduced heme and heme/copper carbonmonoxy species
Kretzer, Ryan M.,Ghiladi, Reza A.,Lebeau, Estelle L.,Liang, Hong-Chang,Karlin, Kenneth D.
, p. 3016 - 3025 (2008/10/08)
Carbon monoxide readily binds to heme and copper proteins, acting as a competitive inhibitor of dioxygen. As such, CO serves as a probe of protein metal active sites. In our ongoing efforts to mimic the active site of cytochrome c oxidase, reactivity toward carbon monoxide offers a unique opportunity to gain insight into the binding and spectroscopic characteristics of synthetic model compounds. In this paper, we report the synthesis and characterization of CO-adducts of (5/6L)FeII, [(5/6L)FeII...CuI](B (C6F5)4), and [(TMPA)CuI(CH3CN)](B(C6 F5)4), where TMPA = tris(2-pyridylmethyl)amine and 5/6L = a tetraarylporphyrinate tethered in either the 5-position (5L) or 6-position (6L) to a TMPA copper binding moiety, Reaction of (5/6L)FeII {in THF (293 K): UV-vis 424 (Soret), 543-544 nm; 1H NMR δpyrrole 52-59 ppm (4 peaks); 2H NMR (from (5L-d8)FeII) δpyrroole 53.3, 54.5, 55.8, 56.4 ppm} with CO in solution at RT yielded (5/6L)FeII-CO {in THF (293 K): UV-vis 413-414 (Soret), 532-533 nm; IR v(CO)Fe 1976-1978 cm-1; 1H NMR δpyrrole 8.8 ppm; 2H NMR (from (5L-d8)FeII-CO) δpyrrole 8.9 ppm; 13C NMR δ(CO)Fe 206.8-207.1 ppm (2 peaks)}. Experiments repeated in acetonitrile, acetone, toluene, and dichloromethane showed similar spectroscopic data. Binding of CO resulted in a change from five-coordinate, high-spin Fe(II) to six-coordinate, low-spin Fe(II), as evidenced by the upfield shift of the pyrrole resonances to the diamagnetic region (1H and 2H NMR spectra), Addition of CO to [(5/6L)FeII...CuI](B (C6F5)4) {in THF (293 K): UV-vis (6L only) 424 (Soret), 546 nm; 1H NMR δpyrrole 54-59 ppm (multiple peaks); 2H NMR (from [(5L-d8)FeII...CuI (B(C6F5)4)) δpyrrole 53.4 ppm (br)} gave the bis-carbonyl adduct [(5/6L)FeIICO...CuI-CO](B (C6F5)4) {in THF (293 K): UV-vis (6L only) 413 (Soret), 532 nm; IR v(CO)Fe 1971-1973 cm-1, v(CO)Cu 2091-2093 cm-1, ～2070(sh) cm-1; 1H NMR δpyrole 8.7-8.9 ppm; 2H NMR (from [(5L-d8)FeII·· ·CuICO](B(C6F5)4)) δpyrole 8.9 ppm; 13C NMR δ(CO)Fe 206.8-208.1 ppm (2 peaks), δCO)Cu 172.4 (5L), 178,2 (6L) ppm}. Experiments in acetonitrile, acetone, and toluene exhibited spectral features similar to those reported, The [(5/6L)FeII-CO··· CuICO](B(C6F5)4) compounds yielded (CO)Fe spectra analogous to those seen for (5/6L)FeII-CO and (CO)Cu, spectra similar to those seen for [(TMPA)CuICO](B(C6F5)4) {in THF (293 K): IR v(CO)Cu, 2091 cm-1, ～2070(sh) cm-1; 13C NMR δ(CO)Cu 180.3 ppm}. Additional IR studies were performed in which the [5L)FeII-CO···CuI-CO] (B(C6F5)4) in solution was bubbled with argon in an attempt to generate the iron-only mono-carbonyl [5L)FeII-CO···Cu] (B(C6F5)4) species; in coordinating solvent or with axial base present, decreases in characteristic IR-band intensities revealed complete loss of CO from copper and variable loss of CO from the heme.
