Red-light photosensitized cleavage of DNA by (L-lysine)(phenanthrolinebase)copper(II) complexes

Patra, Ashis K and Nethaji, Munirathinam and Chakravarty, Akhil R (2005) Red-light photosensitized cleavage of DNA by (L-lysine)(phenanthrolinebase)copper(II) complexes. In: Dalton Transactions (16). pp. 2798-2804.

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Abstract

Ternary copper(II) complexes $[Cu(L-lys)B(ClO_{4})](ClO_{4})$ (1-4), where B isa heterocyclic base, viz. 2,2'-bipyridine (bpy, 1), 1,10-phenanthroline(phen, 2), dipyrido[3,2-d: 2',3'-f]quinoxaline (dpq, 3) anddipyrido[3,2-a:2', 3'-c] phenazene (dppz, 4), are prepared and their DNA binding and photo-induced DNA cleavage activity studied(L-lys=L-lysine). Complex 2, structurally characterized by X-ray crystallography, shows a square-pyramidal (4+1) coordination geometry in which the N,O-donor L-lysine and N,N-donor heterocyclic base bind at the basal plane and the perchlorate ligand is bonded at the elongated axial site. The crystal structure shows the presence of a pendant cationic amine moiety-$(CH_{2})_{4}NH_{3}+$ of L-lysine. The one-electron paramagnetic complexes display a d-d band in the range of 598-762 nm in DMF and exhibit cyclic voltammetric response due to Cu(II)/Cu(I) couple in the range of 0.07 to -0.20 V vs. SCE in DMF-Tris-HCl buffer. The complexes having phenanthroline bases display good binding propensity to the calf thymus DNA giving an order:4(dppz) > 3(dpq) > 2(phen)1(bpy). Control cleavage experiments using pUC19 supercoiled DNA and distamycin suggest major groove binding for the dppz and minor groove binding for the other complexes. Complexes 2-4 show efficient DNA cleavage activity on UV (365 nm) or visible light (694 nm ruby laser) irradiation via a mechanistic pathway involving formation of singlet oxygen as the reactive species. The amino acid L-lysine bound to the metal shows photosensitizing effect at red light, while the heterocyclic bases are primarily DNA groove binders. The dpq and dppz ligands display red light-induced photosensitizing effects in copper-bound form.

Item Type:	Journal Article
Publication:	Dalton Transactions
Publisher:	Royal Society of Chemistry
Additional Information:	Copyright for this article belongs to Royal Society of Chemistry.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	19 Sep 2005
Last Modified:	19 Sep 2010 04:20
URI:	http://eprints.iisc.ac.in/id/eprint/3665

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