title: Potency of photoinduced electron transfer and antioxidant efficacy of pyrrole and pyridine based Cu(II)-Schiff complexes while binding with CT-DNA.
abstract: Here we report a systematic and comparative study to define a correlation between the structure and function of a series of simple, biologically active small inorganic Schiff base copper complexes for the occurrence of charge transfer phenomenon in calf thymus DNA (CT-DNA) using transient absorption spectroscopy corroborated with magnetic field effect. Four copper(II) Schiff base complexes with differently substituted heterocyclic ligands with antioxidant activity have been used. The binding constants of the order of ∼ 10(4) support the moderate binding affinity of the complexes towards CT-DNA. The methyl-substituted pyrrole complex shows maximum binding affinity (Kb: 8.33 × 10(4)) compared to others. The occurrence of photoinduced electron transfer (PET) from CT-DNA to pyrrole containing complexes has been confirmed by identifying the corresponding transient radical ions whereas the extent of PET with pyridine substituted complexes is too small to be observed. The increase of the yield of radical ions in presence of magnetic field depicts that the initial spin correlation in geminate radical ion pair is triplet. The difference between experimental and calculated B½ values, the measure of hyperfine interactions (HFI) present in the system, arises due to hole hopping through intrastrand and interstrand DNA bases. The unsubstituted pyrrole complexes cleave DNA much more than the methyl-substituted one. Therefore, the probability of intrastrand superexchange increases with methyl-substituted complexes, that reduces the rate of hole hopping and hence the B½ value.
authors.affiliation: Chemical Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India.
authors.forename: Banabithi
authors.initials: B
authors.lastname: Koley Seth
authors.affiliation: Chemical Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India.
authors.forename: Aurkie
authors.initials: A
authors.lastname: Ray
authors.affiliation: Crystallography and Molecular Biology, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India.
authors.forename: Arpita
authors.initials: A
authors.lastname: Saha
authors.affiliation: Crystallography and Molecular Biology, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India.
authors.forename: Partha
authors.initials: P
authors.lastname: Saha
authors.affiliation: Chemical Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India. Electronic address: samita.basu@saha.ac.in.
authors.forename: Samita
authors.initials: S
authors.lastname: Basu
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D002417:Cattle; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D003300:Copper / Q000737:chemistry*; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D053837:DNA Cleavage / Q000187:drug effects / Q000528:radiation effects; D004579:Electron Transport; D010782:Photolysis; D011725:Pyridines / Q000737:chemistry; D011758:Pyrroles / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D000975:Antioxidants; D056831:Coordination Complexes; D011725:Pyridines; D011758:Pyrroles; D012545:Schiff Bases; D003300:Copper; D004247:DNA; C427203:calf thymus DNA; C023666:pyridine
keywords: Antioxidant activity; B(½) values; DNA cleavage; DNA hopping; Laser flash photolysis; Magnetic field effect