Interactions Of Ruthenium Complexes With Ct-DNA And G-quadruplex DNA

Due to their intriguing photophysical,photochemical and biological activities,the ruthenium（II）polypyridine complexes are regared as promising candicates for anticancer reagents,and have received considerable attention in bioinorganic chemistry.This dissertation focuses on the interactions of three ruthenium（II）polypyridine complexes with calf thymus DN A（ct-DNA）and G-quadruplex DN A.（1）The interactions of ruthenium complexes 1,2,3 with ct-DNA has been investigated by UV-visible absorption titrations,emission spectroscopy titrations,steady-state emission quenching,ethidium bromide competition,DNA thermal denaturation,salt effects,viscosity measurements,agarose gel electrophoresis and DFT method.Complexes 1 and 3 bond to ct-DNA by partial intercalation,while complex 2 bond to DN A via a groove mode.The binding constants of the complexes1,2,3 with ct-DNA are K_b（1）=2.1×10⁶ M^-1,K_b（2）=2.7×10⁶ M^-1,K_b（3）=2.3×10⁶ M^-1,with binding strength 2>3>1.Complex 2 emitted weak luminescence in neutral aqueous solution,while upon successive additions of ct-DNA,the luminescence of the complex revived sharply by a factor of 6.3（I/I₀）,behaving as a sensitive DNA molecular light switch.Complexes 2 and 3 had a photocleavage effect on p BR322 DNA,and the cleaving efficiency was demonstrated to be 2>3.（2）The interactions of ruthenium complexes 1,2,3 with G-quadruplex DNA has been investigated by UV-vis and fluorescence spectroscopy,circular dichroism（C D）spectroscopy,fluorescence resonance energy transfer（FRET）melting assay,polymerase chain reaction（PCR）stop assay,fluorescent intercalator displacement（FID）titrations,Job plot and color reaction studies.It was found that complexes 1 and3 could not induce HTG21 to form quadruplex structure,whereas complex 2 could promote the formation of antiparallel G-quadruplex without Na⁺and K⁺present,and convert the preformed parallel G-quadruplex into the antiparallel type G-quadruplex under K⁺condition.Complex 2 acted as a promising photophysical"light switch"for G-quadruplex DN A,with 8.6 and 8.4 fold fluorescence enhancements in Na⁺and K⁺buffers,respectively.