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Resonance Raman and absorption characterization of cationic Co(II)‐porphyrin in its complexes with nucleic acids: binding modes, nucleic base specificity and role of water in Co(II) oxidation processes
Author(s) -
Terekhov Sergei N.,
Galievsky Victor A.,
Chirvony Vladimir S.,
Turpin PierreYves
Publication year - 2005
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1391
Subject(s) - polynucleotide , chemistry , porphyrin , intercalation (chemistry) , nucleic acid , cationic polymerization , guanine , aqueous solution , resonance raman spectroscopy , dna , ionic strength , raman spectroscopy , stereochemistry , crystallography , polymer chemistry , inorganic chemistry , photochemistry , organic chemistry , nucleotide , biochemistry , physics , optics , gene
A comparative study of Co(II) and Co(III) complexes of the water‐soluble cationic tetrakis( N ‐methyl‐4‐pyridiniumyl)porphyrin [Co II ‐ and Co III TMpyP(4)] with calf thymus DNA (CT DNA) and synthetic double‐stranded (ds) and single‐stranded (ss) polynucleotides, namely, poly(dA‐dT) 2 , poly(dG‐dC) 2 , [poly(dA)·poly(dT)], poly(A), poly(dT), poly(G) and poly(C) was carried out by resonance Raman (RR) as well as stationary absorption spectroscopy. It is shown that free Co II TMpyP(4) in aqueous solution is easily oxidized to Co III TMpyP(4) by dissolved molecular oxygen, but Co(II) to Co(III) oxidation ability fundamentally changes when Co II TMpyP(4) is bound to nucleic acids (NA). In double helical DNA and AT‐containing polynucleotides, where the porphyrin is assumed to be outside bound mainly in the minor groove near AT sites, Co(II) is stable for weeks and even months. It is suggested that Co(II) axial ligation by immobilized water (i.e. water molecule that is hydrogen bound to O or N atoms from DNA bases) results in such Co II TMpyP(4) stabilization. In contrast, Co II TMpyP(4) binding with ds and ss guanine‐containing polynucleotides results in instantaneous Co(II) to Co(III) transformation. This can be explained by Co ion ligation by the guanine N7 atoms, which are known to be strong electron‐donating ligands. It is assumed that partial intercalation occurs when Co II TMpyP(4) is bound with poly(dG‐dC) 2 , in particular, at low ionic strength values, where cobalt ion is Co(III) in character. Copyright © 2005 John Wiley & Sons, Ltd.