Probing secondary coordination sphere interactions within porphyrin-cored polymer nanoparticles

A suite of zinc porphyrin-cored polymeric nanoparticles were synthesized and characterized to study secondary coordination sphere interactions. We show that with proper design these materials catalyze the reaction of cyanide with N,N-dimethylformamide.

Reactivity of inorganic sulfide species towards a pentacoordinated heme model system

The reactivity of inorganic sulfide towards ferric bis(N-acetyl)- microperoxidase 11 in sodium dodecyl sulfate has been explored by means of visible absorption and resonance Raman spectroscopies. The reaction has been previously studied in buffered solutions at neutral pH and in the presence of excess sulfide, revealing the formation of a moderately stable hexacoordinated low spin ferric sulfide complex that yields the ferrous form in the hour's timescale. In the surfactant solution, instead, the ferrous form is rapidly formed. The spectroscopic characterization of the heme structure in the surfactant milieu revealed the stabilization of a major ferric mono-histidyl high spin heme, which may be ascribed to out of plane distortions prompting the detachment of the axially ligated water molecule, thus leading to a differential reactivity. The ferric bis(N-acetyl)- microperoxidase 11 in sodium dodecyl sulfate provides a model for pentacoordinated heme platforms with an imidazole-based ligand.

Hemeproteins as Targets for Sulfide Species

Significance: Sulfides are endogenous and ubiquitous signaling species that share the hemeproteins as biochemical targets with O₂, nitric oxide, and carbon monoxide. The description of the binding mechanisms is mandatory to anticipate the biochemical relevance of the interaction. Recent Advances: The binding of sulfide to ferric hemeproteins has been described in more than 40 systems, including native proteins, mutants, and model systems. Mechanisms of sulfide binding to ferric hemeproteins have been examined by a combination of kinetic and computational experiments. The distal control of the association process, dissected into the migration of the ligand to the active site and the binding event, reveals that neutral hydrogen sulfide (H₂S) reaches the active site and is the predominant binding ligand, while the HS^- is excluded by the protein matrix. Experiments with model compounds, devoid of a protein scaffold, reveal that both H₂S and HS^- can bind the ferric heme if accessing the site. A critical role of the proximal ligand in the prevention of the metal-centered reduction has been experimentally assessed. For metmyoglobin and methemoglobin, the coordination of sulfide leads to noncanonical functions: sulfide storage and its oxidative detoxification have been evidenced under physiological and excess sulfide concentrations, respectively. Critical Issues: The bound species is suggested to predominate in the monoprotonated form, although spectroscopic evidence is pending. Future Directions: A description of the role of hemeproteins as biochemical targets for inorganic sulfide requires understanding the reactivity of bound sulfide, for example: the metal-centered reduction, the reaction with excess sulfide, oxidants, or other gasotransmitters, among other biomolecules.

Hydrosulfide complexes of the transition elements: diverse roles in bioinorganic, cluster, coordination, and organometallic chemistry

Molecules containing transition metal hydrosulfide linkages are diverse, spanning a variety of elements, coordination environments, and redox states, and carrying out multiple roles across several fields of chemistry.

Activity adaptability of a DhHP-6 peroxidase-mimic in wide pH and temperature ranges and solvent media

Deuterohemin-β-Ala-His-Thr-Val-Glu-Lys (DhHp-6): peroxidase with high activity.

Structure advantage and peroxidase activity enhancement of deuterohemin-peptide–inorganic hybrid flowers

Hybridizing deuterohemin-peptide (DhHP-6) with copper phosphate to form hybrid flowers was prepared for preventing DhHP-6 aggregation.