INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
A surface effect allows HNO / NO discrimination at the nanomolar level by a cobalt porphyrin bound to gold.
SEBASTIAN A. SUÁREZ; MARIANO H FONTICELLI; ALDO A RUBERT; EZEQUIEL DE LA LLAVE; DAMIÁN A. SCHERLIS; ROBERTO C. SALVAREZZA; MARCELO A MARTI; FABIO A DOCTOROVICH
AMER CHEMICAL SOC
Año: 2010 p. 8536 - 8536
Nitroxyl (HNO) is a small short-lived molecule for which it has been suggested that it could be produced, under certaincofactors conditions, by nitric oxide (NO) synthases. Biologically relevant targets of HNO are heme proteins, thiols,molecular oxygen, NO, and HNO itself. Given the overlap of the targets and reactivity between NO and HNO, it is verydifficult to discriminate their physiopathological role conclusively, and accurate discrimination between them stillremains critical for interpretation of the ongoing research in this field. The high reactivity and stability of cobalt(II)porphyrins toward NO and the easy and efficient way of covalently joining porphyrins to electrodes through S-Aubonds prompted us to test cobalt(II) 5,10,15,20-tetrakis[3-(p-acetylthiopropoxy)phenyl]porphyrin [Co(P)], as apossible candidate for the electrochemical discrimination of both species. For this purpose, first, we studied thereaction between NO, NO donors, and commonly used HNO donors, with CoII(P) and CoIII(P). Second, we covalentlyattached CoII(P) to gold electrodes and characterized its redox and structural properties by electrochemical techniquesas well as scanning tunneling microscopy, X-ray photoelectron spectroscopy, and solid-state density functional theorycalculations. Finally, we studied electrochemically the NO and HNO donor reactions with the electrode-bound Co(P).Our results show that Co(P) is positioned over the gold surface in a lying-down configuration, and a surfaceeffect is observed that decreases the CoIII(P) (but not CoIII(P)NO-) redox potential by 0.4 V. Using thisinformation and when the potential is fixed to values that oxidize CoIII(P)NO- (0.8 V vs SCE), HNO can be detected byamperometric techniques. Under these conditions, Co(P) is able to discriminate between HNO and NO donors,reacting with the former in a fast, efficient, and selective manner with concomitant formation of the CoIII(P)NO-complex, while it is inert or reacts very slowly with NO donors.