Structural alteration of low pH, low temperature induced protonated form of DNA to the canonical form by the benzophenanthridine alkaloid nitidine: Spectroscopic exploration

• Published in: International journal of biological macromolecules Vol. 119; pp. 1106 - 1112
• Main Authors: Haque, Lucy, Bhuiya, Sutanwi, Giri, Indrajit, Chowdhury, Susmita, Das, Suman
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.11.2018
• Subjects: Alkaloid-DNA interaction; Animals; Base Pairing - drug effects; Benzophenanthridines - pharmacology; Cattle; DNA - chemistry; Hydrogen-Ion Concentration; Nucleic Acid Denaturation; Protons; Spectrum Analysis; Structural conversion; Switching of base pairs; Temperature; Alkaloid-DNA interaction; Structural conversion; Switching of base pairs
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2018.08.031

Polymorphism of DNA plays a very important part of research relating to the drug-DNA interactions. Here main focus of our investigation is to monitor the interaction of the benzophenanthridine plant alkaloid, nitidine (NIT) with two different forms of DNA i.e. B-DNA and protonated form of DNA maintaining proper temperatures and buffer conditions. Binding interaction of NIT was ascertained from the UV–Visible spectroscopic and spectrofluorimetric titration experiments. Binding constants of the interactions of NIT with different polymorphic forms were calculated from UV-absorption study. The binding constants were 3.8 × 105 M−1 and 1.3 × 105 M−1 for B-DNA and protonated DNA respectively. Red shift in the absorption maxima of NIT on binding with DNA, comparatively greater relative quenching of fluorescence intensity of free NIT than bound NIT, perturbation in the CD spectrum of DNA in presence of NIT confirmed the mode of binding as intercalation. Moreover, spectropolarimetric experiment confirms that left handed protonated form of DNA gets partially converted to the canonical B form of DNA while binds with NIT. Besides the CD experiment, thermal melting experiment also showed that on binding with NIT stabilization of protonated DNA was increased to an appreciable extent. •The interactions of nitidine (NIT) with B and protonated forms of DNA are investigated using different spectroscopic techniques.•The binding affinity of NIT with both forms of DNA are more or less same in our experimental condition.•The mode of binding was intercalation as confirmed from quenching data.•NIT stabilizes the structure of protonated DNA and a sequential conversion of left-handed protonated form to right handed B-form is found .