Picket fence porphyrins. Synthetic models for oxygen binding hemoproteins

Abstract

Model iron(II) porphyrin complexes for the active site of myoglobin and oxymyoglobin have been synthesized and fully characterized by Mossbauer, electronic, and infrared spectral analysis, magnetic susceptibility, and X-ray crystallography. The synthesis is reported for the "picket fence porphyrin," mero-tetra(a,a,a',a-o-pivalamidophenyl)porphyrin, which has great steric bulk creating a nonprotic cavity on one side of the porphyrin. The unsaturated ferrous complex, 1, reacts with strong field ligands to give six-coordinate, diamagnetic complexes, 2. The complexes, 2, react reversibly with oxygen, in solution at 25°. Crystalline diamagnetic dioxygen complexes, 3, having 1-methylimidazole or 1-n-butylimidazole as axial ligands were isolated and characterized. The complex, 3, contains O2 bound "end-on" with an Fe-O-O angle of 136 (4)°. A dioxygen complex with tetrahydrofuran as an axial base, 4, was also prepared and appears to be paramagnetic (2.4 BM). Carbonyl complexes with imidazoles (i-co = 1965 cm-1) and THF (veo = 1955 cm-1) as axial ligands are all diamagnetic.The dioxygen complexes, 3 and 4, show no vo2 at 25°but a strong, sharp band is seen at 1385 cm-1 at -175°. The complexes are thus described as containing coordinated singlet ( ) oxygen. The remarkable stability of the complexes, 3 and 4, and their Mossbauer and spectral properties are discussed.

Quinine and Chloroquine Differentially Perturb Heme Monomer−Dimer Equilibrium

“…Results using water are found to be identical to those obtained using DMSO or an additional reporter molecule such as tert-butyl alcohol. The molar susceptibility of FPIX is converted to magnetic moment using the following equation: (2) Results and Discussion Proton NMR spectra at acidic (pH 3) and basic (pH 9) 95% (v/v) DMSO-d 6 solutions have been obtained to elucidate further what the above limiting values of the magnetic moment mean in terms of which FPIX species are present. These proton NMR spectra are shown in Figure 2.…”

UV-Vis, Fluorescence, and EPR Studies of Porphyrins in Bilayers of Dioctadecyldimethylammonium Surfactants

“…Therefore, any observed fluorescence intensity originates from aggregates which contain only zinc porphyrins. Assuming a statistical distribution of zinc and copper porphyrins in the aggregates, the relative fluorescence intensity ( / / / 0) is given by eq 1 ,in which I 0 is the fluorescence intensity of aggregates r/I0 = (nzf (1) of pure zinc porphyrin, nZn is the mole fraction of zinc porphyrin, and N is the average aggregation number of the porphyrins. The experiments were carried out at a high porphyrin concentration (R = 5 X 10~3), thus almost all porphyrin molecules are aggregated.…”

Cationic porphyrins as probes of DNA structure

“…The Mn+3 complex of meso-tetra-(N-methyl-4-pyridiniumyl) porphine, Mn-T4MpyP, was synthesized as earlier described (18). All unmetallated compounds were characterized by proton nmr and optical spectroscopes as well as through reference to their chromatographic Rf values (20 Tris-Cl, 50 mM NaCl, and 100 mM MgCl2; 5.0 pL of Aci I (10 units/pL); 2.0 pL of 0-mercaptoethanol; 5.0 pL of bovine serum albumin (1 pg/pL); 38 PL of deionized water. After reacting at 37°C for 8 hr, 50 pL of the 70% glycerol solution described above was added and the mixture was loaded into a nondenaturing 8% polyacrylamide (29:1 acrylamide: bis-acrylamide) gel and electrophoresed for 6 hr at 600 V. Following electrophoresis, the gel was subjected to autoradiography and the appropriate band corresponding to the 138 base pair fragment was excised from the gel.…”