title: Red-light photosensitized cleavage of DNA by (l-lysine)(phenanthroline base)copper(II) complexes.
abstract: Ternary copper(II) complexes [Cu(l-lys)B(ClO4)](ClO4)(1-4), where B is a heterocyclic base, viz. 2,2'-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 3) and dipyrido[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 -(CH2)4NH3+ 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.
authors.affiliation: Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Ashis K
authors.initials: AK
authors.lastname: Patra
authors.forename: Munirathinam
authors.initials: M
authors.lastname: Nethaji
authors.forename: Akhil R
authors.initials: AR
authors.lastname: Chakravarty
mesh_terms: D000818:Animals; D002417:Cattle; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000528:radiation effects*; D004269:DNA, Bacterial / Q000737:chemistry / Q000528:radiation effects*; D008027:Light; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010777:Photochemistry; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D009942:Organometallic Compounds; D003300:Copper; D004247:DNA; C427203:calf thymus DNA