title: Spectroscopic studies on the interaction between Pr(III) complex of an ofloxacin derivative and bovine serum albumin or DNA.
abstract: The binding properties on [PrL2(NO3)](NO3)2 (L=9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperaziny)-7-oxo-7Hpyrido[1,2,3-de]-1,4-benzoxazine-6-carbaldehyde benzoyl hydrazone) to bovine serum albumin (BSA) have been studied for the first time using fluorescence spectroscopy in combination with UV-Vis absorbance spectroscopy. The results showed that [PrL2(NO3)](NO3)2 strongly quenched the intrinsic fluorescence of BSA through a static quenching procedure, and non-radiation energy transfer happened within molecules. The number of binding site was about 1, and the efficiency of Förster energy transfer provided a distance of 4.26 nm between tryptophan and [PrL2(NO3)](NO3)2 binding site. At 288, 298, 310 K, the quenching constants of BSA-[PrL2(NO3)](NO3)2 system were 5.11×10(4), 4.33×10(4) and 3.71×10(4) l M(-1). ΔH, ΔS and ΔG were obtained based on the quenching constants and thermodynamic theory (ΔH<0, ΔS>0 and ΔG<0). These results indicated that hydrophobic and electrostatic interactions are the mainly binding forces in the [PrL2(NO3)](NO3)2-BSA system. In addition, the CD spectra have proved that BSA secondary structure changed in the presence of [PrL2(NO3)](NO3)2 in aqueous solution. Moreover, the interaction between [PrL2(NO3)](NO3)2 and calf thymus DNA (CT DNA) was studied by spectroscopy and viscosity measurements, which showed that the binding mode of the [PrL2(NO3)](NO3)2 with DNA is intercalation. The DNA cleavage results show that in the absence of any reducing agent, the [PrL2(NO3)](NO3)2 can cleave plasmid pBR322 DNA and its hydrolytic mechanism was demonstrated with hydroxyl radical scavengers and singlet oxygen quenchers.
authors.affiliation: Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, PR China.
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.forename: Zhao-Rong
authors.initials: ZR
authors.lastname: Ma
authors.forename: Liang
authors.initials: L
authors.lastname: Huang
authors.forename: Feng-Juan
authors.initials: FJ
authors.lastname: Chen
authors.forename: Zheng-zhi
authors.initials: ZZ
authors.lastname: Zeng
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D004247:DNA / Q000378:metabolism*; D004583:Electrons; D004735:Energy Transfer; D004996:Ethidium / Q000737:chemistry; D007700:Kinetics; D015242:Ofloxacin / Q000737:chemistry / Q000378:metabolism*; D011193:Potassium Iodide / Q000737:chemistry; D011221:Praseodymium / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012492:Salts / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D017186:Titrimetry; D014783:Viscosity
chemical_list: D012492:Salts; D011193:Potassium Iodide; D012710:Serum Albumin, Bovine; D004247:DNA; D015242:Ofloxacin; D004996:Ethidium; D011221:Praseodymium