title: Interaction of anticancer drug mitoxantrone with DNA hexamer sequence d-(CTCGAG)2 by absorption, fluorescence and circular dichroism spectroscopy.
abstract: The interaction of mitoxantrone with d-(CTCGAG)2 has been studied by absorption, fluorescence and circular dichroism (CD) spectroscopy. The hypochromism and quenching of fluorescence showed that about four mitoxantrone molecules may be binding externally to DNA hexamer sequence at high drug to nucleic (D/N) acid duplex ratios (28.0-1.1). At lower D/N ratios (1.0-0.2), a red shift in absorption maxima at 610 and 660 nm by 15 and 20 nm, respectively and a red shift in emission maxima by 11 nm accompanied by increase in absorbance and emission has been observed. The equilibrium constant for binding at low (1.0-0.2) and high (28.0-1.1) D/N ratios is 1.8×10(5) M(-1) and 1.38×10(6) M(-1), respectively. The CD spectra show change in intensity of bands accompanied by appearance of induced bands at 325 nm and 650-700 nm. The 251 nm band shows blue shift at D/N ratio of 0.25 and 0.5. The binding isotherms show stoichiometry of 0.25 and 0.5 mitoxantrone molecules binding per duplex. The results suggest stacking of aromatic chromophore of mitoxantrone with terminal base pair of DNA strand forming a sandwiched structure of mitoxantrone between four and two duplex molecules. These investigations are relevant to the formation of ternary complex with topoisomerase enzyme and hence an understanding of anti tumor action of mitoxantrone.
authors.affiliation: Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur 177 001, India.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Dogra
authors.forename: Pamita
authors.initials: P
authors.lastname: Awasthi
authors.forename: Maya
authors.initials: M
authors.lastname: Nair
authors.forename: Ritu
authors.initials: R
authors.lastname: Barthwal
mesh_terms: D000042:Absorption; D000970:Antineoplastic Agents / Q000737:chemistry*; D001483:Base Sequence; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry; D007364:Intercalating Agents / Q000737:chemistry; D008942:Mitoxantrone / Q000737:chemistry*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013057:Spectrum Analysis
chemical_list: D000970:Antineoplastic Agents; D007364:Intercalating Agents; D009838:Oligodeoxyribonucleotides; D004247:DNA; D008942:Mitoxantrone