Interaction study of some macrocyclic inorganic schiff base complexes with calf thymus DNA using spectroscopic and voltammetric methods Maryam Bordbar a, * , Fariba Tavoosi b , Ali Yeganeh-Faal b , Mohammad Hasan Zebarjadian c a Department of Chemistry, Faculty of Science, University of Qom, Qom, Iran b Department of Chemistry, Faculty of Science, Payame Noor University, Iran c Farhangian University, Shahid Magsoudi Branch, Hamedan, Iran article info Article history: Received 18 June 2017 Received in revised form 22 September 2017 Accepted 22 September 2017 Available online 23 September 2017 Keywords: DNA Spectrophotometry Cyclic voltammetry Spectrofluorometry Partial intercalation interaction abstract The interaction of Cd(II), Zn(II) and Mn(II)-L (4,8-bis(2-pyridylmethyl)-4,8-diazaundecane-1,11-diamine) transition metal complexes with calf thymus DNA (CT-DNA) has been investigated using electronic, fluorescence and circular dichroism (CD) spectroscopy, thermal denaturation and cyclic voltammetry (CV). Based on the UVeVis study, binding constants of the complexes with CT-DNA were calculated. Changes in the band of the CD spectrum, DNA melting temperature and in the ipa and ipc of the complexes in the presenceCT-DNA, overall, showed that the studied complex exhibited good DNA interaction ability with partial intercalation mode. © 2017 Elsevier B.V. All rights reserved. 1. Introduction The development of novel metal containing anticancer thera- peutic agents has always been one of the main objectives of me- dicinal chemistry. The successful application of organo-transition metal compounds in fighting against diseases; especially cancer, has made the design of organometallic based pharmaceuticals increasingly interesting [1]. Deoxyribonucleic acid (DNA) is gener- ally the primary intracellular target of anticancer drugs. Most of the hereditary information is carried by DNA, which simplifies the synthesis of biological proteins and enzymes via replication and transcription of the hereditary information [2]. Therefore, DNA binding transition metal complexes have been extensively studied as DNA structural probes, DNA dependent electron transfer probes, DNA foot printing and sequence specific cleaving agents as well as potential anticancer drugs [3,4]. Thus, the interaction between transition metal compounds and DNA may damage DNA in cancer cells through blocking their division and leading to cell death [5]. Considering their various pharmacological applications including animal tumor inhibition, Schiff bases, categorized as privileged li- gands, have been extensively investigated [6]. Schiff bases, which contain such donor atoms as N and O, are structurally similar to neutral biological systems and are used in the clarification of the mechanism of transformation of rasemination reaction in biological systems given the presence of azomethine linkage (C]N) [7,8]. Most transition metal ions may interact with over two different sites and their interactions with DNA is more complicated. Transi- tion metal ions often indirectly bind to the phosphate groups and directly bind to the bases, which contain purine N 7 or pyrimidine N 3 atoms [9]. A lot of transition metal complexes have been considered for potential applications as DNA structure probes, mediation agents for strand scission of duplex DNA and chemo- therapeutic agents [10-13]. Transition metals generally play a very significant role in organisms and their complexes can interact non- covalently with nucleic acids by intercalation, groove binding or external electrostatic binding for cations [5]. Various methods such as UVeVisible [14,15], fluorescence [16] and circular dichroism (CD) [17] spectroscopy, equilibrium dialysis [18] and potentiometry [19,20] have been used to investigate the binding of various ligands to macromolecules. Among these methods, equilibrium dialysis is used widely; but it requires the analysis of free and total drug concentration and takes a long time. In potentiometric method, ion selective electrodes are used. These electrodes have the lack of selectivity for many ligand [19,20]. The fluorescence measurements can provide some useful information about macromolecule-ligand * Corresponding author. Tel.: þ98 2532103792; fax: þ98 25 32850953. E-mail address: m.bordbare@gmail.com (M. Bordbar). Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc https://doi.org/10.1016/j.molstruc.2017.09.088 0022-2860/© 2017 Elsevier B.V. All rights reserved. Journal of Molecular Structure 1152 (2018) 128e136