title: New insights into the mechanism of the DNA/doxorubicin interaction.
abstract: Doxorubicin (DOX) is an important anthracycline antibiotic whose intricate features of binding to DNAs, not yet fully understood, have been the object of intense debate. The dimerization equilibrium has been studied at pH = 7.0, I = 2.5 mM, and T = 25 °C. A thermodynamic and kinetic study of the binding of doxorubicin to DNA, carried out by circular dichroism, viscometry, differential scanning calorimetry, fluorescence, isothermal titration calorimetry, and T-jump relaxation measurements, has enabled us to characterize for the first time two different types of calf thymus DNA (ctDNA)/DOX complexes: PD1 for C(DOX)/C(DNA) < 0.3, and PD2 for higher drug content. The nature of the PD1 complex is described better in light of the affinity of DOX with the synthetic copolymers [poly(dA-dT)]2 and [poly(dG-dC)]2. The formation of PD1 has been categorized kinetically as a two-step mechanism in which the fast step is the groove binding in the AT region, and the slow step is the intercalation into the GC region. This bifunctional nature provides a plausible explanation for the high PD1 constant obtained (K1 = 2.3 × 10(8) M(-1)). Moreover, the formation of an external aggregate complex ctDNA/DOX (PD2) at the expense of PD1, with K2 = 9.3 × 10(5) M(-1), has been evinced.
authors.affiliation: Universidad de Burgos , Departamento de Química, 09001 Burgos, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Pérez-Arnaiz
authors.forename: Natalia
authors.initials: N
authors.lastname: Busto
authors.forename: José M
authors.initials: JM
authors.lastname: Leal
authors.forename: Begoña
authors.initials: B
authors.lastname: García
mesh_terms: D000818:Animals; D002417:Cattle; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D018736:DNA Adducts / Q000737:chemistry*; D004317:Doxorubicin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011067:Poly dA-dT / Q000737:chemistry / Q000378:metabolism; D011089:Polydeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism; D013816:Thermodynamics; D044366:Transition Temperature; D014783:Viscosity
chemical_list: D018736:DNA Adducts; D011089:Polydeoxyribonucleotides; C031902:doxorubicin-DNA; D011067:Poly dA-dT; C019530:poly(dC-dG); D004317:Doxorubicin; D004247:DNA; C427203:calf thymus DNA