SAR and DFI studies of supramolecular tetraammoniumplatinate + DNA matrix with UV/Vis spectrophotometry and physicochemical analysis at 298.15 K R.K. Ameta 1 , Man Singh 1 School of Chemical Sciences, Central University of Gujarat, Gandhinagar 382030, India abstract article info Article history: Received 25 March 2013 Received in revised form 20 September 2013 Accepted 8 November 2013 Available online 19 November 2013 Keywords: Supramolecule Hyperchromic Intercalation DNA helix DFI SAR DNA binding activity of bis(benzyldimethylalkylazaniumyl) tetrachloroplatinumdiuide supramolecular complexes (MBKs) was studied at 298.15 K with UV/Vis spectrophotometric and physicochemical methods. In UV/Vis spectrophotometric method, absorbance at λ max = 260 nm has inferred a hyperchromic effect for explaining intercalating nature of MBKs. DNA binding constant in spectrophotometric titrations for intercalating strength of complexes has shown stronger intercalating activities of MBK8 and MBK12. Density, sound velocity and refractive index of DNA have been studied before and after interaction with MBKs with their stronger interaction. Isentropic and apparent molal compressibilities have inferred that the supramolecular interactions cause distortion of DNA helix. The relative viscosity of DNA-MBKs inferred intercalation of MBKs with DNA due to an aromatic ring in MBKs. DFI relationship shows lowering in surface tension and increases in viscosity data of DNA-MBKs solution, and explained their interaction pattern. This DFI study explained their structure–activity relationship (SAR) as well as their anticancer nature. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Serendipitous discovery of cis-diamminedichloridoplatinum (II) is popularly known as cisplatin that has introduced platinum complexes in the field of chemotherapy. Later, many platinum based drugs have developed and undergone in vitro and in vivo analysis, reportedly, some of them reached upto clinical level 1 . Not only cisplatin analogous but also supramolecular platinum salts have signif- icant historical importance in area of medicinal sciences [1,2]. Many platinum salts are being used to cure various categories of human cancers; however, their side-effects like nephrotoxicity and drug resistance restrict their wider uses [3,4]. Previously [5], we have re- ported metallosupramolecular ionic network of tetraammoniumplatinate [(C 6 H 5 CH 2 N(CH 3 ) 2 (C n H 2n + 1 )] 2 + [PtCl 4 ] 2− (MBK8, MBK10, MBK12 and MBK14) depicted in Fig. 1, where benzalkonium chloride (BKC) was selected as cationic part of tetraammoniumplatinate complexes (TC), which has huge biological applications [6]. BKC is used as a cationic surfac- tant for rapid and prolonged incorporation into cell lipid membranes [7,8]. With its huge applicability in medicinal areas, it is considered at trials in transmission of HIV [9]. Apart from synthesis, the DNA binding study is a practical approach, through which, the medicinal applications of complexes are identified such as anticancer activity, because binding with DNA is a primary molecular target of any anticancer drugs [10]. Thereby, the DNA binding with platinum complexes have been widely ex- amined during past several decades, due to, their use as potential antican- cer drugs, DNA structural probes, DNA-dependent electron transfer probes, DNA foot printing, sequence-specific cleaving agents and so on have in hot discussion [10–12]. Thus, the DNA targeted metal based drugs involving non-covalent DNA binding; particularly metallo- intercalators have drawn attention in advancement of efficient anticancer drugs [13]. Considering such specification, the investigation of DNA bind- ing activity of TC has been our main concern, and in the present study, we reported DNA binding study of TC which is analyzed with UV/Vis spectrophotometric and physicochemical method. Such contributions could be helpful in designing novel ionic complexes of platinum which could be an asset in medical or pharmaceutical progressions. 2. Experimental section 2.1. Materials and methods Synthesized bis(benzyldimethyloctylazaniumyl) tetrachloro- platinumdiuide (MBK8), bis(benzyldimethyldecylazaniumyl) tetra- chloroplatinumdiuide (MBK10), bis(benzyldimethyldodecylazaniumyl) tetrachloroplatinumdiuide (MBK12) and bis(benzyldimethyltetra- decylazaniumyl) tetrachloroplatinumdiuide (MBK14) are studied for DNA interaction. Table 1 furnishes information about the chemicals used in this study whose purification was checked with chromatographic method and the water contents were checked with Karl Fischer. The Milli-Q water (Millipore SAS 67/20 Mosheim) Journal of Molecular Liquids 190 (2014) 200–207 E-mail addresses: ametarakesh40@gmail.com (R.K. Ameta), mansingh50@hotmail.com (M. Singh). 1 Tel.: +91 79 23260210; fax: +91 79 23260076. 0167-7322/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molliq.2013.11.009 Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq