engleski

Detailed 17O-NMR kinetic study of water exchange of water-soluble manganese(III) porphyrins

Oxidative stress (OS) is common to numerous diseases, including cancer. Among other, OS is mediated by the activity of superoxide dismutases (SOD), natural proteins that catalyze dismutation of the superoxide anion. SOD-activity can efficiently be mimicked by various compounds including Mn porphyrins. A thorough study of protolytic speciation of manganese ortho- (MnTE-2-PyP) and meta-tetrakis(N-ethylpyridinium-3-yl)porphyrin (MnTE-3-PyP) complexes revealed that in aqueous solutions within the pH range 2–13 the complexes could be mono- and di-deprotonated. The rate constants of the water-exchange reactions of MnIIITE-2-PyP5+ in slightly acidic aqueous medium (pH = 6.0) have also been reported along with the corresponding activation parameters. In highly basic solutions (pH = 12) MnIIITE-2-PyP5+ complex shown no measurable relaxivity enhancement indicating that dominant porphyrin species at this pH must be the one which coordinates neither the aqua nor hydroxo ligand, i.e. in which axially coordinated to the central Mn(III) is only an oxo ligand . As a continuation of our previous studies we present a systematic 17O-NMR kinetic study of pH-dependence of the water exchange of MnIIITE-2-PyP5+ and MnIIITE-3-PyP5+ complexes in the pH range 2-13.

ganese(III) porphyrins; water exchange; 17O NMR

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