Universidad de Burgos , Departamento de Química, 09001 Burgos, Spain.
J Phys Chem B. 2014 Feb 6;118(5):1288-95. doi: 10.1021/jp411429g. Epub 2014 Jan 24.
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.
多柔比星（DOX）是一种重要的蒽环类抗生素，其与 DNA 结合的复杂特征尚未完全阐明，这一直是激烈争论的焦点。在 pH = 7.0、I = 2.5 mM 和 T = 25°C 的条件下，已经研究了二聚平衡。通过圆二色性、粘度测定、差示扫描量热法、荧光、等温滴定量热法和 T 跳跃弛豫测量，对多柔比星与 DNA 的结合进行了热力学和动力学研究，使我们能够首次表征两种不同类型的小牛胸腺 DNA（ctDNA）/DOX 复合物：C（DOX）/C（DNA）<0.3 时为 PD1，药物含量较高时为 PD2。根据 DOX 与合成共聚物[poly(dA-dT)]2 和[poly(dG-dC)]2 的亲和力，更好地描述了 PD1 复合物的性质。PD1 的形成在动力学上被归类为两步机制，其中快速步骤是在 AT 区域的沟结合，而缓慢步骤是在 GC 区域的插入。这种双功能性质为获得的高 PD1 常数（K1 = 2.3×10(8) M(-1)）提供了一个合理的解释。此外，还证明了以 PD1 为代价形成外部聚集复合物 ctDNA/DOX（PD2）的形成，K2 = 9.3×10(5) M(-1)。
