Observation of the reversibility of a covalent pyrrolobenzodiazepine (PBD) DNA adduct by HPLC/MS and CD spectroscopy
作者:Khondaker M. Rahman、Colin H. James、David E. Thurston
DOI:10.1039/c0ob00762e
日期:——
Pyrrolobenzodiazepines (PBDs) are sequence-selective DNA minor-groove binding agents that covalently bond to guanine with a reported preference for Pu-G-Pu sequences (Pu = Purine). Using HPLC/MS and Circular Dichroism (CD) methodologies, we have established for the first time that the aminal bond formed between PBD molecules and DNA is reversible. Furthermore, we have shown that while the rate of aminal bond cleavage does not depend on the sequence preference of a PBD molecule for a particular binding site, the rate of re-formation of the PBD-DNA adduct does. We have also shown that the PBD anthramycin (2) appears to be an exception to this rule in that, during cleavage from the DNA, its C-ring aromatizes and it cannot then re-attach due to a loss of electrophilicity at the C11-position. Although the C-ring aromatization of anthramycin has been previously reported to occur in the absence of DNA and after treatment with trifluoroacetic acid (TFA), in this case no pH lowering was required, with the DNA itself appearing to catalyse the process.
吡咯并苯并二氮杂卓(PBD)是一种序列选择性DNA小沟结合剂,能与鸟嘌呤共价结合,且据称对Pu-G-Pu序列(Pu = 嘌呤)有偏好。我们利用HPLC/MS和圆二色性(CD)方法首次证实了PBD分子与DNA之间形成的氨基键是可逆的。此外,我们还发现,虽然氨基键断裂的速度不取决于PBD分子对特定结合位点的序列偏好,但PBD-DNA加合物重新形成的速度却与此相关。我们还发现,PBD蒽霉素(2)似乎是一个例外,在从DNA断裂的过程中,其C环芳香化,由于C11位失去亲电性,因此无法重新结合。虽然此前有报告称,蒽霉素的C环芳香化发生在没有DNA且经过三氟乙酸(TFA)处理的情况下,但在这种情况下,不需要降低pH值,DNA本身似乎可以催化这一过程。