15442-64-5Relevant articles and documents
Zinc (II) porphyrins as viable scaffolds to stabilize hydrogen sulfide binding at the metal center
Strianese, Maria,Mirra, Silvia,Lamberti, Marina,Pellecchia, Claudio
, p. 426 - 431 (2017)
H2S is an important biological messenger but its reactivity and physiological concentrations are largely controversial. On the other hand, reactivity of H2S with biologically relevant metal scaffolds for the selective tracking of H2S in biological fluids is underexplored. In this work we investigated interaction of monohydrogensulfide with a series of zinc porphyrins by 1H NMR, UV–vis and ESI mass experiments. The results provide evidence that HS? binds the metal center for all the investigated complexes.
EPR studies of the dynamics of rotation of dioxygen in model cobalt(II) hemes and cobalt-containing hybrid hemoglobins
Bowen, James H.,Shokhirev, Nikolai V.,Raitsimring, Arnold M.,Buttlaire, Daniel H.,Walker, F. Ann
, p. 8683 - 8691 (1997)
Earlier we showed that the shapes of the EPR spectra of cobalt(II) porphyrinate(nitrogen base)(dioxygen) complexes in fluid solution were sensitive to the rate of rotation about the Co-O bond (Walker, F. A.; Bowen, J. H. J. Am. Chem. Soc. 1985, 107, 7632). We have now extended these studies to four metal-substituted hybrid hemoglobins in an attempt to determine whether EPR spectroscopy is sensitive to differences in the mobility of dioxygen in the α and β subunits of the T and R quaternary states. For purposes of this study, [α2(CoO2)β2(FeO2)] and [α2(FeO2)β2(CoO2)] were used as R-state models and [α2(CoO2)β2(Zn)] and [α2(Zn)β2(CoO2)] were used as T-state models. EPR spectra were recorded for samples of each of the above hybrids, equilibrated with 1 atm of O2 gas, as a function of temperature. The progress toward averaging of the EPR signals of the Co-O2-containing subunits was measured as the difference in field positions, ΔH, for the midpoint of the low- and high-field extrema of the derivative EPR spectra. A plot of ΔH vs temperature for each hybrid shows that the [α2(Zn)β2(CoO2)] hybrid is unique in averaging more slowly than the other three (all of which behave similarly), indicating more restricted rotation of dioxygen in T-state β-chain pockets than in the heme distal O2-binding pockets of any other form. This finding is consistent with X-ray crystallographic data which show that valine E11 on the distal side of the T-state β-chain pocket partially blocks the dioxygen binding site (Perutz, M. F.; Fermi, G.; Luisi, B.; Shaanan, B.; Liddington, R. C. Acc. Chem. Res. 1987, 20, 309). Simulation of EPR spectra as a function of jump time provides semiquantitative estimates of the rate of dioxygen rotation in these mixed-metal hemoglobin-dioxygen samples; these rates are in the 1 × 108 s-1 range for three of the hybrids at 35-37°C, and about one-third that value for T-state β(CoO2) centers. These results provide new insight into the highly dynamic nature of dioxygen bound to the metal centers of hemoglobin at physiological temperatures.
Photosensitized H2 generation from "one-pot" and "two-pot" assemblies of a zinc-porphyrin/platinum nanoparticle/protein scaffold
Clark, Emily R.,Kurtz, Donald M.
, p. 630 - 638 (2016/01/09)
We report photosensitized H2 generation using a protein scaffold that nucleates formation of platinum nanoparticles (Pt NPs) and contains "built-in" photosensitizers. The photosensitizers, zinc-protoporphyrin IX or zinc-mesoporphyrin IX (ZnP) were incorporated in place of the naturally occurring heme in the 24-subunit iron storage protein bacterioferritin (Bfr) when the ZnPs were added to the E. coli expression medium. We engineered a stable dimeric Bfr variant with two protein subunits sandwiching a ZnP. Ten glycines were also substituted in place of residues surrounding the vinyl side of the porphyrin in order increase access of solvent and/or redox agents. An optimized "one-pot" reaction of this glycine-substituted ZnMP-Bfr dimer with a Pt(iv) salt and borohydride resulted in a ～50 : 50 mixture of protein in the form of Pt-free glycine-substituted ZnP-Bfr dimers and re-assembled 24-mers surrounding Pt NPs formed in situ. H2 production occurred upon visible light irradiation of this "one-pot" product when combined with triethanolamine as sacrificial electron donor and methyl viologen as electron relay. An analogous "two-pot" system containing mixtures of separately prepared Pt-free glycine-substituted ZnP-Bfr dimer and porphyrin-free Pt NP@Bfr 24-mer also showed robust photosensitized H2 generation. The glycine-substituted-ZnP-Bfr dimer thus served as photosensitizer for catalytic reduction of methyl viologen by triethanolamine, and the reduced methyl viologen was able to transfer electrons across the Bfr 24-mer protein shell to generate H2 at the enclosed Pt NP in a "dark" reaction. Our results demonstrate that Bfr is a readily manipulatable and versatile scaffold for photosensitized redox chemistry.
