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Metal‐complex formation and DNA interaction of 5, 10,15,20‐tetrakis(1‐methyl‐4‐pyridiyl)‐porphine: Study of the mechanistic aspects
Author(s) -
Aydinoglu Sabriye,
Biver Tarita,
Secco Fernando,
Venturini Marcella
Publication year - 2010
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.20465
Subject(s) - chemistry , porphyrin , intercalation (chemistry) , copper , metal , ligand (biochemistry) , kinetic energy , base (topology) , kinetics , stereochemistry , nucleic acid , shuffling , free base , crystallography , photochemistry , inorganic chemistry , organic chemistry , computer science , programming language , mathematical analysis , biochemistry , physics , receptor , mathematics , salt (chemistry) , quantum mechanics
Abstract The macrocyclic porphyrin 5,10,15,20‐tetrakis(1‐methyl‐4‐pyridiyl)‐porphine is studied in its ability to coordinate Cu(II) even at very low pH values and to interact, as a copper complex, with calf‐thymus (CT‐DNA). The kinetics and equilibria for metal‐ligand complexes formation are spectrophotometrically studied, particularly focussing on the mechanistic information provided by the kinetic approach. The rate constants of complex formation is much lower than that of water exchange at Cu(II); this behavior is ascribed to an equilibrium between two porphyrin populations, only one of them being reactive. Concerning the interaction of the copper–porphyrin complex (D) with CT‐DNA, it has been found that the complex binds to G–C base pairs by intercalation while forms external complex with the A–T base pairs. The kinetic results agree with a reaction mechanism that takes into account the slow shuffling from an AT‐bound form (DAT) to a GC‐bound form (DGC) of the copper complex (D), finally leading to a more stable DGC* intercalated form. Kinetic and equilibrium parameters for the copper complex binding to the nucleic acid are obtained, and the binding mechanism is discussed. A mechanism is proposed where D reacts simultaneously with (G–C) and (A–T) base pairs. The resulting bound forms interconvert according to a “shuffling” process, which involves formation of an intermediate (DGC) form. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 79–89, 2010