A unique family of stable and water-soluble S-nitrosothiol complexes

In this work, we present a complete and detailed experimental characterization and theoretical study of a variety of coordinated S-nitrosothiols (RSNOs), such as cysteine derivatives, mercaptosuccinic acid, benzyl thiol, and phenyl thiol. Some of them are extremely unstable and sensitive in free form. Strikingly, in contrast with free S-nitrosothiols, we found that, upon coordination to iridium, they become very stable even in aqueous solutions. The study of these coordinated complexes provides further insight on the elucidation of structural aspects dealing with the nature of the S-N bond in RSNOs, a fact which still remains a matter of controversy.

Glutathionato-S-Gold(III) complexes formed as intermediates in the reduction of auricyanide by glutathione

The reduction of auricyanide ([Au(CN)(4)](-), a potential gold(III) metabolite of antiarthritic gold(I) compounds), by glutathione (G(-)SH, an anionic biological reductant) proceeds through two intermediates (I(230) and I(290)) which have previously been identified by their UV-vis spectra, but not isolated. Negative-ion electrospray ionization-mass spectroscopy (ESI-MS) has unambiguously identified them as [Au(CN)(3)(SG)](2-) and [Au(CN)(2)(SG)(2)](3-), respectively, and allowed their formation and decay to be monitored. The spectra also confirm that the products are aurocyanide ([Au(CN)(2)](-), a known metabolite of chrysotherapy agents) and oxidized glutathione (GSSG(2-)). The reactions are dependent on the presence or absence of buffering agents and the pH of the reaction media. The reaction can be driven to the first intermediate by using an excess of auricyanide or by running the reaction at low pH which prevents further reaction. At neutral pH and/or with excess of glutathione present, the reaction proceeds to the second intermediate, which is then reduced to aurocyanide. The monoanions, [Au(CN)(3)(SGH)](-) at m/z=581.2 and [Au(CN)(2)(SGH)(2)](-) at m/z=861.5 generate more intense signals than their respective dianions, [Au(CN)(3)(SG)](2-) at m/2=290.2 and [Au(CN)(2)(SG)(SGH)](2-)m/2=430.9, respectively, whereas the trianion [Au(CN)(2)(SG)(2)](3-) (m/3=281.2) was not observed. These studies demonstrate the value of ESI-MS methods for characterizing reactions of metallopharmaceuticals under biomimetic conditions and suggest that they will be useful for other systems which give strong ESI-MS signals.

Biomedical implications of information processing in chemical systems: Non-classical approach to photochemistry of coordination compounds

Analogies between photoactive nitric oxide generators and various electronic devices: logic gates and operational amplifiers are presented. These analogies have important biological consequences: application of control parameters allows for better targeting and control of nitric oxide drugs. The same methodology may be applied in the future for other therapeutic strategies and at the same time helps to understand natural regulatory and signaling processes in biological systems.