Carcinine (p-alanyl-histamine) is a naturai imidazole-containing compound found in the non-protein fraction of mammalian tissues, probably involved in the carnosine-histidine-histamine metabolic pathway and in the mammalian physiologic response to stress. Carcinine has a good potential to act as a naturai antioxidant in vivo since it is able to scavenge harmful OH radicals and inhibit fatty acid peroxidation. Since transition metal ions, such as Cu(ll), can catalyze the formation of reactive oxygen species resulting in oxidative tissue damage, the chelation of transition metals can be one of the mechanisms by which antioxidants protect targets from oxidative stress preventing them from participating in deleterious processes. Consequently, more information on the interaction of copper (II) with carcinine can shed light on the biologica! role of this dipeptide and aid metal-enzyme studies, since the tautomerism of the imidazole ring can play a cruciai role in enzymatic mechanism. The ability of carcinine to chetate Cu(ll) ions was tested by Raman and IR spectroscopy at different pH values. Both the Raman and IR spectra present some marker bands useful for the identifìcation of the complex structure predominating at a specific pH. In particular, Raman spectroscopy appears to be a useful tool for analyzing the tautomeric equilibrium of the imidazole ring. The neutral imidazole group of this dipeptide gives rise to some bands that appear at different wavenumbers, depending on whether the imidazole ring is in the NT-H (tautomer I) or the Nn-H (tautomer II) protonated form. Both at pH 7 and 9 the tautomer I is preferred in the free ligand, but the tautomeric preference can be completely upset after the complex formation. At neutra! pH NT- and N-ligated complexes were identified, whereas at basic pH the predominant species is an oligopeptide where the imidazole moiety of carcinine binds two different Cu(ll) ions since Nt and Nn nitrogens are both deprotonated.
Vibrational study of the copper(II)-carcinine complexes and tautomerism of imidazole side chain / A. Torreggiani; M. Reggiani; A. Tinti. - STAMPA. - (2006), pp. 150-150. (Intervento presentato al convegno XXVIII European Congress on Molecular Spectroscopy tenutosi a Istanbul (Turkey) nel 3-8 September, 2006).
Vibrational study of the copper(II)-carcinine complexes and tautomerism of imidazole side chain.
REGGIANI, MATTEO;TINTI, ANNA
2006
Abstract
Carcinine (p-alanyl-histamine) is a naturai imidazole-containing compound found in the non-protein fraction of mammalian tissues, probably involved in the carnosine-histidine-histamine metabolic pathway and in the mammalian physiologic response to stress. Carcinine has a good potential to act as a naturai antioxidant in vivo since it is able to scavenge harmful OH radicals and inhibit fatty acid peroxidation. Since transition metal ions, such as Cu(ll), can catalyze the formation of reactive oxygen species resulting in oxidative tissue damage, the chelation of transition metals can be one of the mechanisms by which antioxidants protect targets from oxidative stress preventing them from participating in deleterious processes. Consequently, more information on the interaction of copper (II) with carcinine can shed light on the biologica! role of this dipeptide and aid metal-enzyme studies, since the tautomerism of the imidazole ring can play a cruciai role in enzymatic mechanism. The ability of carcinine to chetate Cu(ll) ions was tested by Raman and IR spectroscopy at different pH values. Both the Raman and IR spectra present some marker bands useful for the identifìcation of the complex structure predominating at a specific pH. In particular, Raman spectroscopy appears to be a useful tool for analyzing the tautomeric equilibrium of the imidazole ring. The neutral imidazole group of this dipeptide gives rise to some bands that appear at different wavenumbers, depending on whether the imidazole ring is in the NT-H (tautomer I) or the Nn-H (tautomer II) protonated form. Both at pH 7 and 9 the tautomer I is preferred in the free ligand, but the tautomeric preference can be completely upset after the complex formation. At neutra! pH NT- and N-ligated complexes were identified, whereas at basic pH the predominant species is an oligopeptide where the imidazole moiety of carcinine binds two different Cu(ll) ions since Nt and Nn nitrogens are both deprotonated.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
