Phillips D R, Greif P C, Boston R C
Department of Biochemistry, La Trobe University, Bundoora, Victoria, Australia.
Mol Pharmacol. 1988 Feb;33(2):225-30.
The dissociation of daunomycin from DNA was examined using a sodium dodecyl sulfate-sequestered stopped flow procedure. Two dissociation processes were observed with calf thymus and bacterial DNA, with approximately 45% of the amplitude associated with the faster process. Both processes were largely independent of DNA sequence for bacterial DNA, comprising 30-70% (G + C) content. The rate of both processes increased by a similar amount with increasing ionic strength. The faster process decreased with decreasing drug loading, whereas the slower process was independent of drug loading. Only one dissociation event was observed for the dissociation of daunomycin from four different synthetic polydeoxynucleotides. All observations are consistent with a parallel model of sodium dodecyl sulfate-induced dissociation of daunomycin from DNA, where the two processes observed reflect two resolvable processes that may be comprised of a series of rate constants for the dissociation of drug from differing environments. The slower process observed with bacterial DNA (0.5-0.7 sec-1) is related to dissociation from preferential 5'-CA DNA-binding sites, whereas the faster process reflects dissociation of drug from lower affinity sites on heterogenous DNA (3.2-4.1 sec-1). Dissociation of daunomycin from four different synthetic polydeoxynucleotides (which did not contain the 5'-CA preferential daunomycin-binding site) exhibited dissociation rates characteristic of low affinity sites (3.3-4.8 sec-1).
使用十二烷基硫酸钠隔离的停流程序研究了柔红霉素从DNA上的解离。在小牛胸腺DNA和细菌DNA中观察到两个解离过程，约45%的幅度与较快的过程相关。对于细菌DNA，这两个过程在很大程度上与DNA序列无关，其（G + C）含量为30 - 70%。随着离子强度的增加，两个过程的速率增加量相似。较快的过程随着药物负载量的减少而降低，而较慢的过程与药物负载量无关。对于柔红霉素从四种不同的合成聚脱氧核苷酸上的解离，仅观察到一个解离事件。所有观察结果都与十二烷基硫酸钠诱导柔红霉素从DNA上解离的平行模型一致，其中观察到的两个过程反映了两个可分辨的过程，这两个过程可能由药物从不同环境中解离的一系列速率常数组成。在细菌DNA中观察到的较慢过程（0.5 - 0.7秒⁻¹）与从优先的5'-CA DNA结合位点解离有关，而较快的过程反映了药物从异源DNA上较低亲和力位点的解离（3.2 - 4.1秒⁻¹）。柔红霉素从四种不同的合成聚脱氧核苷酸（不包含5'-CA优先柔红霉素结合位点）上的解离表现出低亲和力位点的解离速率特征（3.3 - 4.8秒⁻¹）。
