title: Iron(III) Schiff base complexes of arginine and lysine as netropsin mimics showing AT-selective DNA binding and photonuclease activity.
abstract: Iron(III) complexes [Fe(L)(2)]Cl (1-3), where L is monoanionic N-salicylidene-arginine (sal-argH for 1), hydroxynaphthylidene-arginine (nap-argH for 2) and N-salicylidene-lysine (sal-lysH for 3), were prepared and their DNA binding and photo-induced DNA cleavage activity studied. Complex 3 as its hexafluorophosphate salt [Fe(sal-lysH)(2)](PF(6)).6H(2)O (3a) was structurally characterized by single crystal X-ray crystallography. The crystals belonged to the triclinic space group P-1. The complex has two tridentate ligands in FeN(2)O(4) coordination geometry with two pendant cationic amine moieties. Complexes 1 and 2 with two pendant cationic guanidinium moieties are the structural models for the antitumor antibiotics netropsin. The complexes are stable and soluble in water. They showed quasi-reversible Fe(III)/Fe(II) redox couple near 0.6V in H(2)O-0.1M KCl. The high-spin 3d(5)-iron(III) complexes with mu(eff) value of approximately 5.9 mu(B) displayed ligand-to-metal charge transfer electronic band near 500nm in Tris-HCl buffer. The complexes show binding to Calf Thymus (CT) DNA. Complex 2 showed better binding propensity to the synthetic oligomer poly(dA).poly(dT) than to CT-DNA or poly(dG).poly(dC). All the complexes displayed chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent and cleaved supercoiled pUC19 DNA to its nicked circular form. They exhibited photo-induced DNA cleavage activity in UV-A light and visible light via a mechanistic pathway that involves the formation of reactive hydroxyl radical species.
authors.affiliation: Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: Mohammed S
authors.initials: MS
authors.lastname: Ameerunisha Begum
authors.forename: Sounik
authors.initials: S
authors.lastname: Saha
authors.forename: Munirathinam
authors.initials: M
authors.lastname: Nethaji
authors.forename: Akhil R
authors.initials: AR
authors.lastname: Chakravarty
mesh_terms: D000225:Adenine / Q000737:chemistry*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry; D001120:Arginine / Q000737:chemistry*; D002417:Cattle; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D053837:DNA Cleavage; D007501:Iron / Q000737:chemistry*; D008239:Lysine / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009429:Netropsin / Q000737:chemistry*; D010777:Photochemistry; D012545:Schiff Bases / Q000737:chemistry*; D013936:Thymidine / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D012545:Schiff Bases; D009429:Netropsin; D004247:DNA; C427203:calf thymus DNA; D001120:Arginine; D007501:Iron; D000225:Adenine; D008239:Lysine; D013936:Thymidine