Interaction of 6 Mercaptopurine with Calf Thymus DNA – Deciphering the Binding Mode and Photoinduced DNA Damage

Abstract

DNA is one of the major intracellular targets for a wide range of anticancer and antibiotic drugs. Elucidating the binding between small molecules and DNA provides great help in understanding drug-DNA interactions and in designing of new and promising drugs for clinical use. The ability of small molecules to bind and interfere with DNA replication and transcription provides further insight into how the drugs control the expression of genes. Interaction of an antimetabolite anticancer drug 6mercaptopurine (6MP) with calf thymus DNA was studied using various approaches like UV-visible spectroscopy, fluorescence spectroscopy, CD, viscosity and molecular docking. UV-visible spectroscopy confirmed 6MP-DNA interaction. Steady state fluorescence experiments revealed a moderate binding constant of 7.48×103 M−1 which was consistent with an external binding mode. Competitive displacement assays further confirmed a non-intercalative binding mode of 6MP which was further confirmed by CD and viscosity experiments. Molecular docking further revealed the minimum energy conformation (−119.67 kJ/mole) of the complex formed between DNA and 6MP. Hence, the biophysical techniques and in-silico molecular docking approaches confirmed the groove binding/electrostatic mode of interaction between 6MP and DNA. Further, photo induced generation of ROS by 6MP was studied spectrophotometrically and DNA damage was assessed by plasmid nicking and comet assay. There was a significant increase in ROS generation and consequent DNA damage in the presence of light.

Synthesis, DNA-Binding and Antibacterial Activity of the Cell-Penetrating Peptide HIV-1 Tat (49-57)

“…In this work, EB was used as the fluorescence probe. The fluorescence intensity of DNA can be enhanced after interaction with EB because EB can intercalate into the DNA base pairs [25][26][27] . Fig.…”

“…The intercalative binding mode generally causes DNA viscosity to increase significantly because [26,30] . As shown in fig.…”

Studying non-covalent drug–DNA interactions

“…3A). The extent of fluorescence quenching of DNA-EB system can be used to determine the extent of intercalation between the molecule and DNA [37,40]. Groove binding and surface binding molecules show no effect on the DNA-EB fluorescence intensity [41,42].…”

Interaction of Two Flavonoids With Calf Thymus Dna: A Multi - Spectroscopic, Electrochemical and Molecular Modelling Approach

“…42 The CD band of DNA at 270-280 nm is assigned to base stacking interactions between the bases and the band at 245 nm is attributed to the polynucleotide helical structure. 43 These bands are caused by the stacking interactions between the bases pairs and the helical suprastructure of the polynucleotide that provides an asymmetric environment for the bases. The secondary structure of DNA is perturbed markedly by the intercalation of small molecules leaving its signature through the conformational changes in the intrinsic CD spectra of ct-(ds) DNA.…”