Electrophilic sulfhydration of 8-nitro-cGMP involves sulfane sulfur.

The formation of 8-SH-cGMP from the reaction between hydrogen sulfide and 8-nitro-guanosine-3',5'-cyclic monophosphate in the presence of thiols does not take place by nucleophilic attack of the hydrosulfide anion, as previously proposed, but first involves the formation of reactive species containing sulfane sulfur, like persulfides.

[Reversible metalation of a bis-disulfide analogue of the Cys*-X-Cys* hepcidin binding site: structural characterisation of the related copper complex]. / Métallation réversible d'un analogue bis-disulfure du site de liaison Cys*-X-Cys* de l'hepcidine: caractérisation structurale du complexe de cuivre associé.

Hepcidin, a 25-amino-acid peptide secreted by the liver, distributed in the plasma and excreted in urine, is a key central regulator of body iron homeostasis. This hormone decreases export of cellular iron by binding to ferroportin, an iron exporter present at the basolateral surface of enterocytes and macrophages (the sites of dietary iron absorption and iron recycling, respectively), inducing its internalization and degradation. Hepcidin contains eight cysteine residues that form four disulfide bridges, which stabilize a hairpin-shaped structure with two beta sheets. We noticed in the sequence of hepcidin a Cys*-X-Cys* motif which can act as a metal binding site able to trap iron and/or copper. We have tested this hypothesis using a pseudopeptidic synthetic bis-disulfide analogue and we have shown that direct metalation of such ligand leads to the formation of a copper(III) complex with the typical N(2)S(2) donor set. This compound crystallizes in the orthorhombic system, space group Imma. The Cu(III) configuration is square planar, built up from two carboximado-N and two thiolato-S donors. This complex is converted back to the bis-disulfide, with release of the copper salt, upon oxidation with iodine.

Bis

The geometry about the Ru atom in the title compound, [Ru(C(9)H(9)N)(2)(C(92)H(108)N(4)O(24))], is approximately tetragonal and the porphyrin ring is nearly planar, while the C-N-R angles [169.3 (3) and 163.9 (3) degrees ] of the isocyanide ligands in the complex are different from the value of 180 degrees expected in the free ligand.