DNA cleavage activity of linear trinuclear copper(II) complexes

DNA cleavage activity of linear trinuclear copper(II) complexes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article DNA cleavage activity of linear trinuclear copper(II) complexes Arup Kumar Das, Susnata Karmakar This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5698961/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Metal ions and metal complexes are important components of nucleic acid biochemistry, participating both in the regulation of gene expression and as therapeutic agents. Cu(II) complexes are important for DNA cleavage, which is essential for the development of anticancer drugs and chemotherapeutic agents. For example, a study revealed that a Cu(II) complex caused double-strand DNA nicks, destabilized the DNA molecule, and disrupted the phosphodiester bonds. Here two trinuclear copper (II) complexes ware synthesized and structurally characterized: [Cu II 3 ( L 2 ) 4 (2picolinate) 2 (OClO 3 ) 2 ](ClO 4 ) 2 •2CH 3 COCH 3 •2CH 3 OH ( 1 ) and [Cu II 3 ( L 2 ) 4 (2,6-dipicolinate) 2 ] (ClO 4 ) 2 •6MeOH•2H 2 O ( 2 ) ( L 2 = 1-benzyl-[3-(2'-pyridyl)] pyrazole; 2-picolinate = 2-pyridinecarboxylic acid; 2,6-dipicolinate = 2,6-pyridinedicarboxylic acid). The binding of copper complexes to plasmid DNA (P-DNA) has been investigated via UV-Visible spectroscopy, which revealed that P-DNA can covalently bind to the complexes. P-DNA cleavage was also investigated via agarose gel electrophoresis in the presence and absence of an oxidative agent (H 2 O 2 ). The effect of the complex concentration on the P-DNA cleavage reaction has also been studied. Both copper complexes show nuclease activity, which significantly depends on the concentrations of the complexes, in the presence of H 2 O 2, likely through an oxidative mechanism whereas they slightly cleave P-DNA in the absence of an oxidative agent. CuII complexes: trinuclear 1-benzyl-[3-(2'-pyridyl)] pyrazole as the terminal ligand Gel electrophoresis DNA cleavage Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction The transition metal complexes were known to have great importance in cancer biology, due to their tunable redox properties and physiological conditions, which make them for the development of novel therapeutic agents. The interactions between metal-ligand complexes and DNA have played a key role in DNA cleavage and protein binding studies [ 1 – 4 ]. Generally, the DNA and drug interaction mechanism can be expressed by the electrostatic attraction forces, intercalation, groove binding as well as the combination of all these modes. In addition, the DNA cleavage which occurs either by hydrolytic and/or oxidative pathways [ 5 ], [ 6 ]. Platinum (Pt) based complexes [cisplatin, ( cis -diamminedichloro-platinum)] were widely used as drugs for cancer therapy because it inhibits the proliferation of cancer cells through binding with DNA molecules [ 7 ], [ 8 ]. However, most of the Pt (II) complexes possess inherent limitations such as side effects, oxidative stress ionic radius causes the cytotoxicity and it acquired resistance phenomena [ 9 – 13 ]. Therefore, the utilization of therapeutic agents with permissible side effects has been extensively explored for the development of chemotherapeutics, which can work effectively against cancer cells. Polynuclear copper complexes are attracting attention because of their interesting magnetic properties and their relevance to the active centers of several metalloproteins [ 14 ], [ 15 ]. Metal complexes that cleave DNA under physiological condition are of current interest for chemists in the development of artificial nucleases [ 16 – 18 ]. Among all of the reported metal complexes, the most attractive class is copper(II) complexes, which have been extensively applied as catalysts due to their efficient cleavage of nucleic acids last two decades [ 19 – 23 ]. The Cu(II) complexes have awesome interest because of their flexible ligand conformations, thus make the oxidative DNA cleavage [ 24 – 32 ]. Transition metal complexes have been extensively studied for their nuclease-like activity [1a], [ 33 ]. Chemical nucleases present some advantages over conventional enzymatic nucleases in that they are smaller in size and thus can reach more sterically hindered regions of a macromolecule. Many of these utilize the redox properties of the metal center and dioxygen to produce active oxygen species that oxidize DNA, yielding direct strand scission or base modification [ 34 – 36 ]. In addition to magnetism, multinuclear copper (II) complexes have been shown to be of considerable interest in DNA cleavage [ 37 – 41 ]. Moreover, because of our interest in polynuclear copper(II) complexes, in a recently published paper [ 42 ], we described the synthesis, crystal structure and magnetic properties of two new linear trinuclear copper (II) complexes [Cu II 3 ( L 2 ) 4 (2picolinate) 2 (OClO 3 ) 2 ](ClO 4 ) 2 •2CH 3 COCH 3 •2CH 3 OH ( 1 ) and [Cu II 3 ( L 2 ) 4 (2,6-dipicolinate) 2 ] (ClO 4 ) 2 •6MeOH•2H 2 O ( 2 ) ( L 2 = 1-benzyl-[3-(2'-pyridyl)] pyrazole; 2-picolinate = 2-pyridinecarboxylate ion and 2,6-dipicolinate = 2,6-pyridinedicarboxylate ion have been used). In this work, we have shown that the trinuclear carboxylate-bridged copper(II) complexes 1 and 2 cleave (P-DNA) efficiently in the presence/absence of hydrogen peroxide. 2. Experimental 2.1. General All reagents were obtained from commercial sources and used as received. 1-Benzyl-[3-(2'-pyridyl)] pyrazole ( L 2 ) was synthesized via the reported procedure and was used for the reaction [ 38 ], [ 39 ]. 2-Pyridine carboxylic acid and 2,6-pyridinedicarboxylic acid and [Cu II (H 2 O) 6 ][ClO 4 ] 2 (prepared from CuCO 3 with HClO 4 ) [ 37 ] were used as commercially available. Triethylamine was used as the base and dimethylformamide (dmf) was used as the solvent. Diethyl ether was used for the vapor diffusion method of crystallization. 2.2. Synthesis of complexes The synthesis of complexes [Cu II 3 (L 2 ) 4 (2picolinate) 2 (OClO 3 ) 2 ](ClO 4 ) 2 •2CH 3 COCH 3 •2CH 3 OH ( 1 ) and [Cu II 3 (L 2 ) 4 (2,6-dipicolinate) 2 ] (ClO 4 ) 2 •6MeOH•2H 2 O ( 2 ) was performed as per the reported procedure, and these complexes were used for the reaction. Full details of the crystal structure refinement have been deposited with the Cambridge Crystallographic Data Center (CCDC). Data collection and refinement details for 1 and 2 are provided in (Table. S1, ESI) (CCDC numbers 2308238 and 2308593 for 1 and 2 , respectively). 2.3. Absorption Titration of the Copper Complex Binding to DNA Absorption titration of complexes 1 and 2 binding to P - DNA was performed by monitoring the absorbance spectra of the complex (120 µ M) in dmf solution in the presence of increasing amounts of P-DNA. As both P-DNA and the copper complex have overlapping transitions below 350 nm, metal complex spectroscopic changes are studied above this wavelength are studied [ 32 ]. 2.4. Cleavage of pMT-puro by Complexes 1–2 A typical reaction was carried out by mixing various concentrations of either Complexes 1 or 2 in dimethylformamide with 1 µL of 1000 ng/µL pMT-puro (Addgene: #17923) in the presence/absence of H 2 O 2 and then increasing the volume to 10 µL with Milli-Q H 2 O. The control samples were treated with equal volumes of dmf instead of the abovementioned compounds. For comparison of cleavage activity, CuSO 4 was used to treat the P-DNA in a similar reaction mixture. The samples were then allowed to incubate at 37 O C for 60 min, followed by the addition of 2 µL of a P-DNA gel loading dye (Thermo Scientific catalogue number: R0611). The entire volume of the mixture was subsequently subjected to electrophoresis on a 0.8% agarose gel in 1X TAE buffer (40 mM Tris, 20 mM acetic acid, and 1 mM EDTA) containing 2 µL/100 ml of ethidium bromide (10 mg/mL) for 30 min at 80 V. The gel was then photographed on a gel documentation system (Syngene Chemi XRQ), and band intensity quantification was performed via Windows software (Gene Tools from Syngene). 3. Results and Discussion 3.1. The Complexes and their general characterization The synthesis of complexes 1 and 2 was achieved following a straightforward synthetic methodology. To bridge the Cu(II) centers 2-picolinate (for 1 ) and 2,6-dipicolinate (for 2 ) were used. Complexes 1 –2 exhibit IR bands ( Fig. S1 , ESI ) assignable to bridging benzoate ( ν (CO 2 – )) [ 43 ], coordinated dmf ( ν (C = O))/MeOH ( ν (OH)) and ν (ClO 4 – ). The compositions of [Cu II 3 ( L 2 ) 4 (2-picolinate) 2 (OClO 3 ) 2 ](ClO 4 ) 2 •2CH 3 COCH 3 •2MeOH ( 1 ) and [Cu II 3 ( L 2 ) 4 (2,6-dipicolinate) 2 ](ClO 4 ) 2 •6MeOH•2H 2 O ( 2 ) were confirmed by single-crystal structural analysis. [Cu II 3 (L 2 ) 4 (2-picolinate) 2 (OClO 3 ) 2 ](ClO 4 ) 2 •2CH 3 COCH 3 •2MeOH ( 1 ) A perspective view of the metal coordination environment in 1 is shown in Fig. 2 . The selected interatomic distances and angles are listed in ( Table. S2, ESI ). X-ray structural analysis revealed that 1 has a centrosymmetric trinuclear structure and utilizes a 2-pyridinecarboxylate, 2-picolinate (1–) bridge. The central Cu2 ion sits on a crystallographically imposed inversion center and hence only half of the trimeric unit is unique and the other half is symmetry related. The asymmetric unit of 1 contains two acetone and two methanol molecules as solvents for crystallization. The Cu1 and Cu1* centers are coordinated by two pyridine nitrogens (N2 and N3) and two pyrazole nitrogens (N4 and N6). Two 2-pyridinecarboxylates bridge the central and two terminal copper(II) centers in syn – anti mode, completing the fifth coordination to Cu1 and Cu1*. The central copper(II) ion Cu2 is coordinated by two nitrogens (N1 and N1*) and two carboxylate oxygens (O1 and O1*) from two 2-pyridinecarboxylates, 2-picolinate (1–). Two transcoordinated oxygens from two perchlorates complete sixfold coordination. Thus, the Cu1 and Cu1* centers have N(pyridine) 2 N'(pyrazole) 2 O(carboxylate), and Cu2 center has N(pyridine) 2 O 2 (carboxylate)O' 2 (perchlorate) coordination. The terminal Cu1 and Cu1* ions assume distorted trigonal bipyramidal ( τ = 0.52; τ assumes values of 0 and 1 for ideal square pyramidal and trigonal bipyramidal geometries, respectively) [ 43 ] and the central Cu2 assumes a grossly octahedral geometry. [Cu II 3 (L 2 ) 4 (2,6-dipicolinate) 2 ](ClO 4 ) 2 •6MeOH•2H 2 O ( 2 ) A perspective view of the metal coordination environment in 2 is shown in Fig. 3 . The selected interatomic distances and angles are listed in ( Table. S2, ESI ). X-ray structural analysis revealed that the structures of 1 and 2 are closely related, and the central Cu2 ion sits on a crystallographically imposed inversion center; hence, only half of the trimeric unit is unique and the other half is symmetry related. The asymmetric unit of 2 contains six methanol molecules and two water molecules as solvents for crystallization. Like that in 1 , 2 has a centrosymmetric trinuclear structure, utilizing a carboxylate bridge, but here, it is provided by 2,6-pyridinedicarboxylate 2,6-dipicolinate (2–). The Cu1 and Cu1* centers are coordinated by two pyridine nitrogens (N3 and N4) and two pyrazole nitrogens (N5 and N6). Two 2,6-dipicolinate (2–) units coordinate to the central Cu2 differently. One 2,6-dipicolinate (2–) coordinates as a tridentate ligand utilizing pyridine nitrogen (N1) and two oxygens (O3 and O3*) from carboxylate arms. The other, 2,6-dipicolinate (2–) coordinates via its pyridine nitrogen (N2) and two carboxylate oxygens (O1 and O1*). These two carboxylate oxygens O1 and O1* bridge ( µ 1,1 -mode) the central Cu2 with terminal Cu1 and Cu1* ions. Notably, the carboxylate bridges in 1 and 2 are different. In 1 , it is syn – anti and in 2 it is µ 1,1 -mode. Thus, the Cu1 and Cu1* centers have N(pyridine) 2 N'(pyrazole) 2 O(carboxylate) and the Cu2 center has N(pyridine) 2 O 4 (carboxylate) coordination. Notably, the coordination environments around the central Cu2 and the carboxylate bridge in 1 and 2 are different. The terminal Cu1 and Cu1* ions assume distorted trigonal bipyramidal ( τ = 0.46) [ 43 ], and the central Cu2 assumes a grossly octahedral geometry. 3.2 Absorption spectra Absorption spectra of 1 and 2 were recorded in dmf. Complexes display crystal-field transitions at 725 nm ( 1 ) and 745 nm ( 2 ) due to their distorted TBP geometry [ 37 ], [ 38 ], [ 44 ] and ligand-to-metal charge-transfer (LMCT) transitions in the range 360–390 nm ( Fig. S2, ESI ). 3.3. Interactions between P-DNA and copper(II) complexes The absorption spectra of the complexes 1 and 2 in the absence and in the presence of P-DNA, at various concentrations were obtained with the aim of studying the binding of complexes with P-DNA. Interactions between P-DNA and the trinuclear complexes 1 and 2 can be observed through hyperchromic data and the shorter-wavelength shift of the d-d maxima of the complexes ( Fig. S3. ESI ). The interaction of P-DNA with [Cu(H 2 O) 6 ] 2+ leads to a small shift to shorter wavelengths and an increase in the absorption intensity of the d-d maxima. This type of change can be explained by the fact that a small percentage of [Cu(H 2 O) 6 ] 2+ is bound in the inner-sphere by the substitution of coordinated water molecules by N donors of P-DNA. Therefore, on the basis of the spectroscopic data, such a binding to P-DNA could be proposed. 3.4. P-DNA Cleavage by Complexes 1 and 2 The ability of the title compounds to cleave P-DNA has been studied by treating P- DNA with pMT-puro followed by gel electrophoresis and image analysis. Complex 2 [Lane 5] presented some degree of P-DNA cleavage even in the absence of a reducing agent, whereas complex 1 did not [Lane 4] (Fig. 4 ). To identify the concentration at which 2 is most efficient, equal amounts of DNA were treated with a gradually increasing concentration (9.5 µM − 76 µM) of the complex (Fig. 5 ). The concentration of 76 µM Cu 3 -2,6-dipicolinate ( 2 ) in dmf [Lane 8] was determined to be the minimum required concentration at which the complex effectively cleaves P-DNA. The control sample treated with equal volumes of dmf [Lane 4] showed no degradation of P-DNA, confirming that it is indeed Cu 3 -2,6-dipicolinate ( 2 ) that cleaves the P-DNA. Cu 3 -2,6-dipicolinate ( 2 ) could also effectively degrade P-DNA at concentrations higher than the identified value of 76 µM (data not shown). The ability of these two complexes to degrade P-DNA at various concentrations in the presence of H 2 O 2 was then evaluated (Fig. 6 ). The concentrations of 19 µM and 38 µM Cu 3 -2,6-dipicolinate ( 2 ), which cannot degrade P-DNA otherwise, were found to effectively do so now, in the presence of 1 µL H 2 O 2 . In addition, 76 µM of Cu 3 -2,6-dipicolinate ( 2 ) conceivably could degrade P-DNA completely in the presence of H 2 O 2 [Lanes 8–10]. Surprisingly, Cu3-2-picolinate ( 1 ), which was unable to degrade DNA previously (Fig. 10), could do so in the presence of 1 µL H 2 O 2 , at all three concentrations of (21 µM, 42 µM and 84 µM [Lanes 5–7] (Fig. 6 ). To compare the ability of 1 and 2 to that of CuSO 4 .5H 2 O, its ability to degrade P-DNA in the presence/absence of H 2 O 2 was checked. Although 320 µM CuSO 4 .5H 2 O could not degrade P-DNA effectively but 1280 µM CuSO 4 .5H 2 O could degrade P-DNA at both these concentrations in the presence of 1 µL H 2 O 2 . 4. Conclusions Two trinuclear Cu(II) complexes [Cu II 3 ( L 2 ) 4 (2-picolinate) 2 (OClO 3 ) 2 ](ClO 4 ) 2 .2CH 3 COCH 3 .2MeOH ( 1 ) and [Cu II 3 II ( L 2 ) 4 (2,6-dipicolinate) 2 ](ClO 4 ) 2 .6MeOH.2H 2 O ( 2 ) have been synthesized and structurally characterized. Herein, we describe cleavage and interaction experiments of these complexes with P-DNA, with the aim of obtaining information about the mechanisms of action involved. The P-DNA cleavage and binding properties of the complexes were investigated via gel electrophoresis and UV–Vis spectroscopy. The experimental results indicate that all the complexes interact with P-DNA and that Cu(II) complexes also cleave P-DNA, probably via an oxidative mechanism. P-DNA cleavage is concentration-dependent. For example, at low concentrations, complex 2 can only undergo scission, but at high concentrations, both complexes degrade the P-DNA into small pieces. Declarations Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Declaration of Interest Statement All the authors in this manuscript, titled ‘ DNA cleavage activity of linear trinuclear copper(II) complexes ’ declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author Statement Arup Kumar Das synthesized complexes 1 and 2 and solved crystal structures also prepared figures. Arup Kumar Das and Susnata Karmakar performed the P-DNA cleavage experiments and manuscript preparation. All the authors were involved in discussing the results and writing the manuscript. Ethics The submitted work should be original and should not have been published elsewhere in any form or language Consent to participate Informed consent was obtained from all individual participants included in the study. Consent to publish The participant has consented to the submission of the case report to the journal. Funding This study was funded by [CSIR] Acknowledgements Financial assistance received from the Council of Scientific & Industrial Research (CSIR), Government of India is gratefully acknowledged. We acknowledge Prof. R. N. Mukherjee (former Prof, of IIT KANPUR and former director of IISER KOLKATA) and Prof. Tapas Kumar Sengupta (IISER KOLKATA) for their valuable suggestions and help. References a) Elena Salvadeo, Lionel Dubois, Jean-Marc Latour. Coordination Chemistry Reviews. 2018, 374, 345–375 b) Jingwen Chen, Xiaoyong Wang, Ying Shao, Jianhui Zhu, Yangguang Zhu, Yizhi Li, Qiang Xu, Zijian Guo, Inorg. Chem. 2007, 46, 8, 3306–3312 María R. Rodríguez, Martín J. Lavecchia, Beatriz S. Parajon-Costa, Ana C. Gonzalez Baro, María R. Gonzalez Baro, Elizabeth R. Cattaneo, Biochimie, 2021, 186, 43–50 S.Y. Yu, S.X. Wang, Q.H. Luo, L.F. Wang, Polyhedron 12 (1993) 1093–1096. Y. Li, J. Zhao, C.C. He, L. Zhang, S.R. Sun, G.C. Xu, J. Inorg. Biochem. 2015, 150, 28–37 C.H. Ng, K.C. Kong, S.T. Von, P. Balraj, P. Jensen, E. Thirthagiri, H. Hamada, M. Chikira, Nucl. Acids Res. 2000, 28, 4856–4864. P. Kumar, B. Baidya, S.K. Chaturvedi, R.H. Khan, B. Mondal, D. Manna, Inorg. Chim. Acta. 2011, 376, 264–270 C. Metcalfe, J.A. Thomas, Chem. Soc. Rev. 2003, 32, 215–224 K.E. Erkkila, D.T. Odom, J.K. Barton, Chem. Rev. 1999, 99, 2777–2796 M.A. Fuertes, C. Alonso, J.M. Perez, Chem. Rev. 2003, 103, 645–662 Y. Sun, S. Gou, R. Yin, P. Jiang, Eur. J. Med. Chem. 2011, 46, 5146–5153 E.P. Swindell, P.L. Hankins, H. Chen, D.U. Miodragovic, T.V. O'Halloran, Inorg. Chem. 2013, 52, 12292–12304 N. Cutillas, G.S. Yellol, C. de Haro, C. Vicente, V. Rodríguez, J. Ruiz, Coord. Chem. Rev. 2013, 257, 2784–2797 R.A. Steiner, D. Foreman, H.X. Lin, B.K. Carney, K.M. Fox, L. Cassimeris, J.M. Tanski, L.A. Tyler, J. Inorg. Biochem. 2014, 137, 1–11 Kahn, O. Molecular Magnetism; VCH: New York, 1993. Suh, M. P.; Han, M. Y.; Lee, J. H.; Min K. S.; Hyeon, C. J. Am. Chem. Soc. 1998, 120, 3819 J. Suh, Acc. Chem. Res. 2003, 36, 562–570. A. Sreedhara, J.A. Cowan, J. Biol. Inorg. Chem. 2001, 6, 337–347 F. Mancin, P. Scrimin, P. Tecilla, U. Tonellato, Chem. Commun. 2005, 2540–2548. M. Brannum, A.K. Tipton, S. Zhu, L.J. Que, J. Am. Chem. Soc. 2001, 123, 1898–1904 F. Medrano, A. Calderon, A.K. Yatsimirsky, Chem. Commun. 2003, 1968–1970 M. Kathryn, T. Deck, A. Tseng, J.N. Burstyn, Inorg. Chem. 2002, 41 669–677 A. Sreedhara, J.D. Freed, J.A. Cowan, J. Am. Chem. Soc. 2000, 122, 8814–8824 R. Ren, P. Yang, W.-J. Zheng, Z.-C. Hua, Inorg. Chem. 2000, 39, 5454–5463 D. Montagner, V. Gandin, C. Marzano, A. Erxleben, J. Inorg. Biochem. 2015, 145, 101–107 D. Gambino, Coord. Chem. Rev. 2011, 255, 2193–2203 D. Crespy, K. Landfester, U.S. Schubert, A. Schiller, Chem. Commun. 2010, 46, 6651–6662 B. Gyurcsik, A. Czene, Future Med. Chem. 2011, 3, 1935–1962 A. Meenongwa, R.F. Brissos, C. Soikum, P. Chaveerach, P. Gamez, Y. Trongpanich, New J. Chem. 2016, 40, 5861–5876 A. Tarushi, J. Kljun, I. Turel, A.A. Pantazaki, G. Psomas, D.P. Kessissoglou, New J.Chem. 2013, 37, 342–355 G.R. Reddy, S. Balasubramanian, K. Chennakesavulu, J. Mater. Chem. A 2014, 2, 15598–15610 N. Chitrapriya, J.H. Shin, I.H. Hwang, Y. Kim, C. Kim, S.K. Kim, RSC Adv. 2015, 5, 68067–68075 M. Gonzalez, Alvarez, G. Alzuet, J. Borras, B. Macıas, and A. Castin eiras. Inorg. Chem. 2003, 42, 2992–2998 Pratviel; G.; Bernadou; J.; Meunier, B. Angew. Chem., Int. Ed. Engl. 1995, 34, 746 Pogozelski, W. K.; Tullius, T. D. Chem. ReV. 1998, 98 , 1089 Burrows, C. J.; Muller, J. G. Chem. ReV. 1998, 98 , 1109 Julian Heinricha, Niklas F. Koniga,b, Sebastian Sobottkaa, Biprajit Sarkara, Nora Kulaka, Journal of Inorganic Biochemistry, 2019, 194, 223–232 A.K. Das, A. De, P. Yadav, F. Lloret, R. Mukherjee, Polyhedron. 2019, 171, 365–373 J. Mukherjee, A. Sengupta, R. Mukherjee, Inorg. Chem. Acta. 2020, 513, 119899 J. Mukherjee, R. Mukherjee, Dalton Trans. 2006, 1611 – 1621 Yan An, Si-Dong Liu, Shu-Yi Deng, Liang-Nian Ji, Zong-Wan Mao Journal of Inorganic Biochemistry. 2006, 100, 1586–1593 Sigman D. S.; Chen, C.-H. B. Chemical Nuclease Activity of 1,10- Phenantrolinecopper. In Metal-DNA Chemistry; Tullius, T. D., Ed.; ACS Symposium Series 402; American Chemical Society: Washington, DC, 1989; Chap. 2 Arup Kumar Das, Sukanta Mandal, Narottam Mukhopadhyay, Francesc Lloret and Rabindranath Mukherjee, ICA, 2025, 577, 122501. T.D. Smith, J.R. Pilbrow, Coord. Chem. Rev. 1974, 13, 173–278 B.J. Hathaway, Copper, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehensive Coordination Chemistry, vol. 5, Pergamon, Oxford, 1987, pp. 533–594. Additional Declarations No competing interests reported. Supplementary Files ESI.pdf Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5698961","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":401838435,"identity":"9dde2551-64bf-4e4c-a6bd-972d1d2cdc7c","order_by":0,"name":"Arup Kumar Das","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYJACZhDBDyISCkjQIiHZANJiQIoWgwMgJjFa+GefMXtcUHGnzvj86sQPDwwY5PnFDuDXInEux9x4xplnEmY33m6WADrMcObsBALWnOExk+ZtOwzUcnYDSEuCwW0CWuTBWv4dljCecXbzD6K0GIC1NByWMODv3UacLYZn2MqNZxw7LDnjBu82iwQDCcJ+kTvDvO1xQc1hfv7+s5tv/qiwkeeXJqAFCNgglARYpQRB5Uha+A8QpXoUjIJRMApGIAAA7jVBT+Fn9iYAAAAASUVORK5CYII=","orcid":"","institution":"Indian Institute of Science Education and Research Kolkata","correspondingAuthor":true,"prefix":"","firstName":"Arup","middleName":"Kumar","lastName":"Das","suffix":""},{"id":401838436,"identity":"904ccb49-7d60-4792-8c92-36528c6c49ef","order_by":1,"name":"Susnata Karmakar","email":"","orcid":"","institution":"Indian Institute of Science Education and Research Kolkata","correspondingAuthor":false,"prefix":"","firstName":"Susnata","middleName":"","lastName":"Karmakar","suffix":""}],"badges":[],"createdAt":"2024-12-23 10:53:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5698961/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5698961/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":73849560,"identity":"de903f9b-eafd-4696-af2b-959cb85e2344","added_by":"auto","created_at":"2025-01-15 09:35:51","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":17377,"visible":true,"origin":"","legend":"\u003cp\u003eLigands of pertinence to this work.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5698961/v1/1609286649e4aa657db7553f.png"},{"id":73849578,"identity":"754fc272-2ef2-483c-85a4-76cf1646efc5","added_by":"auto","created_at":"2025-01-15 09:35:52","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":339986,"visible":true,"origin":"","legend":"\u003cp\u003ePerspective view of the coordination environment in [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(L\u003csup\u003e2\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2-picolinate)\u003csub\u003e2\u003c/sub\u003e(OClO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e•2CH\u003csub\u003e3\u003c/sub\u003eCOCH\u003csub\u003e3\u003c/sub\u003e•2MeOH (\u003cstrong\u003e1\u003c/strong\u003e). Only the donor atoms are labeled and the hydrogen atoms are omitted for clarity.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5698961/v1/99402f5ec4be799d3af831d9.png"},{"id":73849565,"identity":"8f33e427-ccd2-40a0-b5df-e68962fb9da2","added_by":"auto","created_at":"2025-01-15 09:35:51","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":258735,"visible":true,"origin":"","legend":"\u003cp\u003ePerspective view of the coordination environment in [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(L\u003csup\u003e2\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2,6-dipicolinate)\u003csub\u003e2\u003c/sub\u003e](ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e•6MeOH•2H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e \u003c/sub\u003e(\u003cstrong\u003e2\u003c/strong\u003e). Only the donor atoms are labeled and the hydrogen atoms are omitted for clarity.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5698961/v1/59f261255d991637feb48a30.png"},{"id":73851604,"identity":"95bec0eb-2452-4a28-be95-e8654b5e2749","added_by":"auto","created_at":"2025-01-15 09:43:51","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":126175,"visible":true,"origin":"","legend":"\u003cp\u003eAgarose gel electrophoresis of pMT-puro P-DNA (1 μL, 100 ng/μL, 34.26 fM) treated with the two compounds. The incubation time was1 hour at 37\u003csup\u003e0\u003c/sup\u003eC. Lane 1: GeneRuler 1 kb Plus P-DNA Ladder. Lane 2: P-DNA. Lane 3: P-DNA treated with 1 μL of dmf. Lane 4: P-DNA treated with 21 μM, 1 μL of Cu3-picolinate.\u0026nbsp; Lane 5: P-DNA treated with 19 μM, 1 μL of Cu3-2,6-dipicolinate.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5698961/v1/32e0567ea0d098dd5d5025fc.png"},{"id":73851608,"identity":"5cdcddbe-17a5-4b4b-9fec-ed53fad1591a","added_by":"auto","created_at":"2025-01-15 09:43:52","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":140246,"visible":true,"origin":"","legend":"\u003cp\u003eAgarose gel electrophoresis of pMT-puro P-DNA (1 μL, 100 ng/μL, 34.26 fM) treated with Cu3-2,6-dipicolinate. The incubation time was 1 hour at 37\u003csup\u003e0\u003c/sup\u003eC. Lane 1: GeneRuler 1 kb Plus P-DNA Ladder. Lane 2: P-DNA. Lane 3: P-DNA treated with 0.5 μL of dmf. Lane 4: P-DNA treated with 4 μLof dmf. Lane 5: P-DNA treated with 19 μM, 0.5 μL of Cu3-2,6-dipicolinate in dmf. Lane 6: P-DNA treated with 19 μM, 1 μL of Cu3-2,6- dipicolinate in dmf. Lane 7: P-DNA treated with 19 μM, 2 μL of Cu3-2,6- dipicolinate in dmf. Lane 8: P-DNA treated with 19 μM, 4 μL of Cu3-2,6- dipicolinate in dmf.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5698961/v1/981c7e86482746b3b1a81980.png"},{"id":73849571,"identity":"335ea776-7f15-490e-9ea0-7f23e9320c77","added_by":"auto","created_at":"2025-01-15 09:35:51","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":141597,"visible":true,"origin":"","legend":"\u003cp\u003eAgarose gel electrophoresis of pMT-puro P-DNA (1 μL, 100 ng/μL, 34.26 fM) being subjected to various treatments. The incubation time was 1 hour at 37\u003csup\u003e0\u003c/sup\u003eC.\u0026nbsp; Lane 1: GeneRuler 1 kb Plus P-DNA Ladder. Lane 2: P-DNA with no treatment. Lane 3: 4 μL of dmf. Lane 4: 1 μL H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Lane 5: 21 μM, 1μL Cu3-2-picolinate in the presence of 1 μL H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Lane 6: 21 μM, 2 μL Cu3-2-picolinate in presence of 1 μL H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Lane 7: 21 μM, 4 μL of Cu3-2-picolinate in the presence of 1 μL H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Lane 8: 19 μM, 1 μL Cu3-2,6-dipicolinate in the presence of 1 μL H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Lane 9: 19 μM, 2 μL Cu3-2,6- dipicolinate in the presence of 1 μL H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Lane 10: 19 μM, 4 μL Cu3-2,6- dipicolinate in the presence of 1 μL H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Lane 11: 320 μM, 1 μL CuSO\u003csub\u003e4\u003c/sub\u003e.5H\u003csub\u003e2\u003c/sub\u003eO. Lane 12: 320 μM, 4 μL CuSO\u003csub\u003e4\u003c/sub\u003e.5H\u003csub\u003e2\u003c/sub\u003eO. Lane 13: 320 μM, 1 μL CuSO\u003csub\u003e4\u003c/sub\u003e.5H\u003csub\u003e2\u003c/sub\u003eO in presence of 1 μL H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. Lane 14: 320 μM, 4 μL CuSO\u003csub\u003e4\u003c/sub\u003e.5H\u003csub\u003e2\u003c/sub\u003eO in presence of 1 μL H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5698961/v1/ed919a979a75cfc7b6e41326.png"},{"id":73853270,"identity":"8c27feaa-c147-4ec3-8ce1-c7fc9e3512d1","added_by":"auto","created_at":"2025-01-15 09:59:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1668888,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5698961/v1/710aecda-082e-48c0-8800-1fb40e8aa548.pdf"},{"id":73849562,"identity":"39da5a49-903b-4e53-9bb7-3adf130c6944","added_by":"auto","created_at":"2025-01-15 09:35:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":291362,"visible":true,"origin":"","legend":"","description":"","filename":"ESI.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5698961/v1/5116e6f757d6adfdc20926cb.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eDNA cleavage activity of linear trinuclear copper(II) complexes\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe transition metal complexes were known to have great importance in cancer biology, due to their tunable redox properties and physiological conditions, which make them for the development of novel therapeutic agents. The interactions between metal-ligand complexes and DNA have played a key role in DNA cleavage and protein binding studies [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Generally, the DNA and drug interaction mechanism can be expressed by the electrostatic attraction forces, intercalation, groove binding as well as the combination of all these modes. In addition, the DNA cleavage which occurs either by hydrolytic and/or oxidative pathways [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Platinum (Pt) based complexes [cisplatin, (\u003cem\u003ecis\u003c/em\u003e-diamminedichloro-platinum)] were widely used as drugs for cancer therapy because it inhibits the proliferation of cancer cells through binding with DNA molecules [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, most of the Pt (II) complexes possess inherent limitations such as side effects, oxidative stress ionic radius causes the cytotoxicity and it acquired resistance phenomena [\u003cspan additionalcitationids=\"CR10 CR11 CR12\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Therefore, the utilization of therapeutic agents with permissible side effects has been extensively explored for the development of chemotherapeutics, which can work effectively against cancer cells.\u003c/p\u003e \u003cp\u003ePolynuclear copper complexes are attracting attention because of their interesting magnetic properties and their relevance to the active centers of several metalloproteins [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Metal complexes that cleave DNA under physiological condition are of current interest for chemists in the development of artificial nucleases [\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Among all of the reported metal complexes, the most attractive class is copper(II) complexes, which have been extensively applied as catalysts due to their efficient cleavage of nucleic acids\u003c/p\u003e \u003cp\u003elast two decades [\u003cspan additionalcitationids=\"CR20 CR21 CR22\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The Cu(II) complexes have awesome interest because of their flexible ligand conformations, thus make the oxidative DNA cleavage [\u003cspan additionalcitationids=\"CR25 CR26 CR27 CR28 CR29 CR30 CR31\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTransition metal complexes have been extensively studied for their nuclease-like activity [1a], [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Chemical nucleases present some advantages over conventional enzymatic nucleases in that they are smaller in size and thus can reach more sterically hindered regions of a macromolecule. Many of these utilize the redox properties of the metal center and dioxygen to produce active oxygen species that oxidize DNA, yielding direct strand scission or base modification [\u003cspan additionalcitationids=\"CR35\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. In addition to magnetism, multinuclear copper (II) complexes have been shown to be of considerable interest in DNA cleavage [\u003cspan additionalcitationids=\"CR38 CR39 CR40\" citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMoreover, because of our interest in polynuclear copper(II) complexes, in a recently published paper [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e], we described the synthesis, crystal structure and magnetic properties of two new linear trinuclear copper (II) complexes [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(\u003cb\u003eL\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2picolinate)\u003csub\u003e2\u003c/sub\u003e(OClO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026bull;2CH\u003csub\u003e3\u003c/sub\u003eCOCH\u003csub\u003e3\u003c/sub\u003e\u0026bull;2CH\u003csub\u003e3\u003c/sub\u003eOH (\u003cb\u003e1\u003c/b\u003e) and [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(\u003cb\u003eL\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2,6-dipicolinate)\u003csub\u003e2\u003c/sub\u003e] (ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026bull;6MeOH\u0026bull;2H\u003csub\u003e2\u003c/sub\u003eO (\u003cb\u003e2\u003c/b\u003e) (\u003cb\u003eL\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;1-benzyl-[3-(2'-pyridyl)] pyrazole; 2-picolinate\u0026thinsp;=\u0026thinsp;2-pyridinecarboxylate ion and 2,6-dipicolinate\u0026thinsp;=\u0026thinsp;2,6-pyridinedicarboxylate ion have been used). In this work, we have shown that the trinuclear carboxylate-bridged copper(II) complexes \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e cleave (P-DNA) efficiently in the presence/absence of hydrogen peroxide.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. General\u003c/h2\u003e \u003cp\u003eAll reagents were obtained from commercial sources and used as received. 1-Benzyl-[3-(2'-pyridyl)] pyrazole (\u003cb\u003eL\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e) was synthesized via the reported procedure and was used for the reaction [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e], [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. 2-Pyridine carboxylic acid and 2,6-pyridinedicarboxylic acid and [Cu\u003csup\u003eII\u003c/sup\u003e(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e6\u003c/sub\u003e][ClO\u003csub\u003e4\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003e (prepared from CuCO\u003csub\u003e3\u003c/sub\u003e with HClO\u003csub\u003e4\u003c/sub\u003e) [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] were used as commercially available. Triethylamine was used as the base and dimethylformamide (dmf) was used as the solvent. Diethyl ether was used for the vapor diffusion method of crystallization.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Synthesis of complexes\u003c/h2\u003e \u003cp\u003eThe synthesis of complexes [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(L\u003csup\u003e2\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2picolinate)\u003csub\u003e2\u003c/sub\u003e(OClO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026bull;2CH\u003csub\u003e3\u003c/sub\u003eCOCH\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003cp\u003e\u0026bull;2CH\u003csub\u003e3\u003c/sub\u003eOH (\u003cb\u003e1\u003c/b\u003e) and [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(L\u003csup\u003e2\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2,6-dipicolinate)\u003csub\u003e2\u003c/sub\u003e] (ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026bull;6MeOH\u0026bull;2H\u003csub\u003e2\u003c/sub\u003eO (\u003cb\u003e2\u003c/b\u003e) was performed as per the reported procedure, and these complexes were used for the reaction. Full details of the crystal structure refinement have been deposited with the Cambridge Crystallographic Data Center (CCDC). Data collection and refinement details for \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e are provided in (Table. S1, ESI) (CCDC numbers 2308238 and 2308593 for \u003cb\u003e1\u003c/b\u003eand \u003cb\u003e2\u003c/b\u003e, respectively).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Absorption Titration of the Copper Complex Binding to DNA\u003c/h2\u003e \u003cp\u003eAbsorption titration of complexes \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e binding to P\u003cb\u003e-\u003c/b\u003eDNA was performed by monitoring the absorbance spectra of the complex (120 \u003cem\u003e\u0026micro;\u003c/em\u003eM) in dmf solution in the presence of increasing amounts of P-DNA. As both P-DNA and the copper complex have overlapping transitions below 350 nm, metal complex spectroscopic changes are studied above this wavelength are studied [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Cleavage of pMT-puro by Complexes 1\u0026ndash;2\u003c/h2\u003e \u003cp\u003eA typical reaction was carried out by mixing various concentrations of either Complexes \u003cb\u003e1\u003c/b\u003e or \u003cb\u003e2\u003c/b\u003e in dimethylformamide with 1 \u0026micro;L of 1000 ng/\u0026micro;L pMT-puro (Addgene: #17923) in the presence/absence of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and then increasing the volume to 10 \u0026micro;L with Milli-Q H\u003csub\u003e2\u003c/sub\u003eO. The control samples were treated with equal volumes of dmf instead of the abovementioned compounds. For comparison of cleavage activity, CuSO\u003csub\u003e4\u003c/sub\u003e was used to treat the P-DNA in a similar reaction mixture. The samples were then allowed to incubate at 37\u003csup\u003eO\u003c/sup\u003eC for 60 min, followed by the addition of 2 \u0026micro;L of a P-DNA gel loading dye (Thermo Scientific catalogue number: R0611). The entire volume of the mixture was subsequently subjected to electrophoresis on a 0.8% agarose gel in 1X TAE buffer (40 mM Tris, 20 mM acetic acid, and 1 mM EDTA) containing 2 \u0026micro;L/100 ml of ethidium bromide (10 mg/mL) for 30 min at 80 V. The gel was then photographed on a gel documentation system (Syngene Chemi XRQ), and band intensity quantification was performed via Windows software (Gene Tools from Syngene).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1. The Complexes and their general characterization\u003c/h2\u003e \u003cp\u003eThe synthesis of complexes \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e was achieved following a straightforward synthetic methodology. To bridge the Cu(II) centers 2-picolinate (for \u003cb\u003e1\u003c/b\u003e) and 2,6-dipicolinate (for \u003cb\u003e2\u003c/b\u003e) were used. Complexes \u003cb\u003e1\u003c/b\u003e\u0026ndash;2 exhibit IR bands (\u003cb\u003eFig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e, ESI\u003c/b\u003e) assignable to bridging benzoate (\u003cem\u003eν\u003c/em\u003e(CO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e)) [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], coordinated dmf (\u003cem\u003eν\u003c/em\u003e(C\u0026thinsp;=\u0026thinsp;O))/MeOH (\u003cem\u003eν\u003c/em\u003e(OH)) and \u003cem\u003eν\u003c/em\u003e(ClO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e). The compositions of [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(\u003cb\u003eL\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2-picolinate)\u003csub\u003e2\u003c/sub\u003e(OClO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026bull;2CH\u003csub\u003e3\u003c/sub\u003eCOCH\u003csub\u003e3\u003c/sub\u003e\u0026bull;2MeOH (\u003cb\u003e1\u003c/b\u003e) and [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(\u003cb\u003eL\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2,6-dipicolinate)\u003csub\u003e2\u003c/sub\u003e](ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026bull;6MeOH\u0026bull;2H\u003csub\u003e2\u003c/sub\u003eO (\u003cb\u003e2\u003c/b\u003e) were confirmed by single-crystal structural analysis.\u003c/p\u003e \u003cp\u003e \u003cem\u003e[Cu\u003c/em\u003e \u003csup\u003e \u003cem\u003eII\u003c/em\u003e \u003c/sup\u003e \u003csub\u003e \u003cem\u003e3\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e(L\u003c/em\u003e \u003csup\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sup\u003e \u003cem\u003e)\u003c/em\u003e \u003csub\u003e \u003cem\u003e4\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e(2-picolinate)\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e(OClO\u003c/em\u003e \u003csub\u003e \u003cem\u003e3\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e)\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e](ClO\u003c/em\u003e \u003csub\u003e \u003cem\u003e4\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e)\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e\u0026bull;2CH\u003c/em\u003e \u003csub\u003e \u003cem\u003e3\u003c/em\u003e \u003c/sub\u003e \u003cem\u003eCOCH\u003c/em\u003e \u003csub\u003e \u003cem\u003e3\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e\u0026bull;2MeOH (\u003c/em\u003e \u003cb\u003e1\u003c/b\u003e \u003cem\u003e)\u003c/em\u003e \u003c/p\u003e \u003cp\u003eA perspective view of the metal coordination environment in \u003cb\u003e1\u003c/b\u003e is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The selected interatomic distances and angles are listed in (\u003cb\u003eTable. S2, ESI\u003c/b\u003e). X-ray structural analysis revealed that \u003cb\u003e1\u003c/b\u003e has a centrosymmetric trinuclear structure and utilizes a 2-pyridinecarboxylate, 2-picolinate (1\u0026ndash;) bridge. The central Cu2 ion sits on a crystallographically imposed inversion center and hence only half of the trimeric unit is unique and the other half is symmetry related. The asymmetric unit of \u003cb\u003e1\u003c/b\u003e contains two acetone and two methanol molecules as solvents for crystallization. The Cu1 and Cu1* centers are coordinated by two pyridine nitrogens (N2 and N3) and two pyrazole nitrogens (N4 and N6). Two 2-pyridinecarboxylates bridge the central and two terminal copper(II) centers in \u003cem\u003esyn\u003c/em\u003e\u0026ndash;\u003cem\u003eanti\u003c/em\u003e mode, completing the fifth coordination to Cu1 and Cu1*. The central copper(II) ion Cu2 is coordinated by two nitrogens (N1 and N1*) and two carboxylate oxygens (O1 and O1*) from two 2-pyridinecarboxylates, 2-picolinate (1\u0026ndash;). Two transcoordinated oxygens from two perchlorates complete sixfold coordination. Thus, the Cu1 and Cu1* centers have N(pyridine)\u003csub\u003e2\u003c/sub\u003eN'(pyrazole)\u003csub\u003e2\u003c/sub\u003eO(carboxylate), and Cu2 center has N(pyridine)\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e(carboxylate)O'\u003csub\u003e2\u003c/sub\u003e(perchlorate) coordination. The terminal Cu1 and Cu1* ions assume distorted trigonal bipyramidal (\u003cem\u003eτ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.52; \u003cem\u003eτ\u003c/em\u003e assumes values of 0 and 1 for ideal square pyramidal and trigonal bipyramidal geometries, respectively) [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e] and the central Cu2 assumes a grossly octahedral geometry.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003e[Cu\u003c/em\u003e \u003csup\u003e \u003cem\u003eII\u003c/em\u003e \u003c/sup\u003e \u003csub\u003e \u003cem\u003e3\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e(L\u003c/em\u003e \u003csup\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sup\u003e \u003cem\u003e)\u003c/em\u003e \u003csub\u003e \u003cem\u003e4\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e(2,6-dipicolinate)\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e](ClO\u003c/em\u003e \u003csub\u003e \u003cem\u003e4\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e)\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e\u0026bull;6MeOH\u0026bull;2H\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e \u003cem\u003eO (\u003c/em\u003e \u003cb\u003e2\u003c/b\u003e \u003cem\u003e)\u003c/em\u003e \u003c/p\u003e \u003cp\u003eA perspective view of the metal coordination environment in \u003cb\u003e2\u003c/b\u003e is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The selected interatomic distances and angles are listed in (\u003cb\u003eTable. S2, ESI\u003c/b\u003e). X-ray structural analysis revealed that the structures of \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e are closely related, and the central Cu2 ion sits on a crystallographically imposed inversion center; hence, only half of the trimeric unit is unique and the other half is symmetry related. The asymmetric unit of \u003cb\u003e2\u003c/b\u003e contains six methanol molecules and two water molecules as solvents for crystallization. Like that in \u003cb\u003e1\u003c/b\u003e, \u003cb\u003e2\u003c/b\u003e has a centrosymmetric trinuclear structure, utilizing a carboxylate bridge, but here, it is provided by 2,6-pyridinedicarboxylate 2,6-dipicolinate (2\u0026ndash;). The Cu1 and Cu1* centers are coordinated by two pyridine nitrogens (N3 and N4) and two pyrazole nitrogens (N5 and N6). Two 2,6-dipicolinate (2\u0026ndash;) units coordinate to the central Cu2 differently. One 2,6-dipicolinate (2\u0026ndash;) coordinates as a tridentate ligand utilizing pyridine nitrogen (N1) and two oxygens (O3 and O3*) from carboxylate arms. The other, 2,6-dipicolinate (2\u0026ndash;) coordinates via its pyridine nitrogen (N2) and two carboxylate oxygens (O1 and O1*). These two carboxylate oxygens O1 and O1* bridge (\u003cem\u003e\u0026micro;\u003c/em\u003e\u003csub\u003e1,1\u003c/sub\u003e-mode) the central Cu2 with terminal Cu1 and Cu1* ions. Notably, the carboxylate bridges in \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e are different. In \u003cb\u003e1\u003c/b\u003e, it is \u003cem\u003esyn\u003c/em\u003e\u0026ndash;\u003cem\u003eanti\u003c/em\u003e and in \u003cb\u003e2\u003c/b\u003e it is \u003cem\u003e\u0026micro;\u003c/em\u003e\u003csub\u003e1,1\u003c/sub\u003e-mode. Thus, the Cu1 and Cu1* centers have N(pyridine)\u003csub\u003e2\u003c/sub\u003eN'(pyrazole)\u003csub\u003e2\u003c/sub\u003eO(carboxylate) and the Cu2 center has N(pyridine)\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e(carboxylate) coordination. Notably, the coordination environments around the central Cu2 and the carboxylate bridge in \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e are different. The terminal Cu1 and Cu1* ions assume distorted trigonal bipyramidal (\u003cem\u003eτ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.46) [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], and the central Cu2 assumes a grossly octahedral geometry.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e\u003cem\u003e3.2 Absorption spectra\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eAbsorption spectra of \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e were recorded in dmf. Complexes display crystal-field transitions at 725 nm (\u003cb\u003e1\u003c/b\u003e) and 745 nm (\u003cb\u003e2\u003c/b\u003e) due to their distorted TBP geometry [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e], [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e] and ligand-to-metal charge-transfer (LMCT) transitions in the range 360\u0026ndash;390 nm (\u003cb\u003eFig. S2, ESI\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Interactions between P-DNA and copper(II) complexes\u003c/h2\u003e \u003cp\u003eThe absorption spectra of the complexes \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e in the absence and in the presence of P-DNA, at various concentrations were obtained with the aim of studying the binding of complexes with P-DNA. Interactions between P-DNA and the trinuclear complexes \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e can be observed through hyperchromic data and the shorter-wavelength shift of the d-d maxima of the complexes (\u003cb\u003eFig. S3. ESI\u003c/b\u003e). The interaction of P-DNA with [Cu(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e leads to a small shift to shorter wavelengths and an increase in the absorption intensity of the d-d maxima. This type of change can be explained by the fact that a small percentage of [Cu(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e6\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e is bound in the inner-sphere by the substitution of coordinated water molecules by N donors of P-DNA. Therefore, on the basis of the spectroscopic data, such a binding to P-DNA could be proposed.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.4. P-DNA Cleavage by Complexes 1 and 2\u003c/h2\u003e \u003cp\u003eThe ability of the title compounds to cleave P-DNA has been studied by treating P- DNA with pMT-puro followed by gel electrophoresis and image analysis. Complex \u003cb\u003e2\u003c/b\u003e [Lane 5] presented some degree of P-DNA cleavage even in the absence of a reducing agent, whereas complex \u003cb\u003e1\u003c/b\u003e did not [Lane 4] (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). To identify the concentration at which \u003cb\u003e2\u003c/b\u003e is most efficient, equal amounts of DNA were treated with a gradually increasing concentration (9.5 \u0026micro;M \u0026minus;\u0026thinsp;76 \u0026micro;M) of the complex (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The concentration of 76 \u0026micro;M Cu\u003csub\u003e3\u003c/sub\u003e-2,6-dipicolinate (\u003cb\u003e2\u003c/b\u003e) in dmf [Lane 8] was determined to be the minimum required concentration at which the complex effectively cleaves P-DNA. The control sample treated with equal volumes of dmf [Lane 4] showed no degradation of P-DNA, confirming that it is indeed Cu\u003csub\u003e3\u003c/sub\u003e-2,6-dipicolinate (\u003cb\u003e2\u003c/b\u003e) that cleaves the P-DNA. Cu\u003csub\u003e3\u003c/sub\u003e-2,6-dipicolinate (\u003cb\u003e2\u003c/b\u003e) could also effectively degrade P-DNA at concentrations higher than the identified value of 76 \u0026micro;M (data not shown).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe ability of these two complexes to degrade P-DNA at various concentrations in the presence of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e was then evaluated (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The concentrations of 19 \u0026micro;M and 38 \u0026micro;M Cu\u003csub\u003e3\u003c/sub\u003e-2,6-dipicolinate (\u003cb\u003e2\u003c/b\u003e), which cannot degrade P-DNA otherwise, were found to effectively do so now, in the presence of 1 \u0026micro;L H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. In addition, 76 \u0026micro;M of Cu\u003csub\u003e3\u003c/sub\u003e-2,6-dipicolinate (\u003cb\u003e2\u003c/b\u003e) conceivably could degrade P-DNA completely in the presence of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e [Lanes 8\u0026ndash;10]. Surprisingly, Cu3-2-picolinate (\u003cb\u003e1\u003c/b\u003e), which was unable to degrade DNA previously (Fig.\u0026nbsp;10), could do so in the presence of 1 \u0026micro;L H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, at all three concentrations of (21 \u0026micro;M, 42 \u0026micro;M and 84 \u0026micro;M [Lanes 5\u0026ndash;7] (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). To compare the ability of \u003cb\u003e1\u003c/b\u003e and \u003cb\u003e2\u003c/b\u003e to that of CuSO\u003csub\u003e4\u003c/sub\u003e.5H\u003csub\u003e2\u003c/sub\u003eO, its ability to degrade P-DNA in the presence/absence of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e was checked. Although 320 \u0026micro;M CuSO\u003csub\u003e4\u003c/sub\u003e.5H\u003csub\u003e2\u003c/sub\u003eO could not degrade P-DNA effectively but 1280 \u0026micro;M CuSO\u003csub\u003e4\u003c/sub\u003e.5H\u003csub\u003e2\u003c/sub\u003eO could degrade P-DNA at both these concentrations in the presence of 1 \u0026micro;L H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eTwo trinuclear Cu(II) complexes [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(\u003cb\u003eL\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2-picolinate)\u003csub\u003e2\u003c/sub\u003e(OClO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.2CH\u003csub\u003e3\u003c/sub\u003eCOCH\u003csub\u003e3\u003c/sub\u003e.2MeOH (\u003cb\u003e1\u003c/b\u003e) and [Cu\u003csup\u003eII\u003c/sup\u003e \u003csub\u003e3\u003c/sub\u003e\u003csup\u003eII\u003c/sup\u003e(\u003cb\u003eL\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2,6-dipicolinate)\u003csub\u003e2\u003c/sub\u003e](ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.6MeOH.2H\u003csub\u003e2\u003c/sub\u003eO (\u003cb\u003e2\u003c/b\u003e) have been synthesized and structurally characterized. Herein, we describe cleavage and interaction experiments of these complexes with P-DNA, with the aim of obtaining information about the mechanisms of action involved. The P-DNA cleavage and binding properties of the complexes were investigated via gel electrophoresis and UV\u0026ndash;Vis spectroscopy. The experimental results indicate that all the complexes interact with P-DNA and that Cu(II) complexes also cleave P-DNA, probably via an oxidative mechanism. P-DNA cleavage is concentration-dependent. For example, at low concentrations, complex 2 can only undergo scission, but at high concentrations, both complexes degrade the P-DNA into small pieces.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of Interest Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the authors in this manuscript, titled \u0026lsquo;\u003cstrong\u003eDNA cleavage activity of linear trinuclear copper(II) complexes\u003c/strong\u003e\u0026rsquo; declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eArup Kumar Das synthesized complexes 1 and 2 and solved crystal structures also prepared figures. Arup Kumar Das and Susnata Karmakar performed the P-DNA cleavage experiments and manuscript preparation. All the authors were involved in discussing the results and writing the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe submitted work should be original and should not have been published elsewhere in any form or language\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent was obtained from all individual participants included in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe participant has consented to the submission of the case report to the journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded by [CSIR]\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFinancial assistance received from the Council of Scientific \u0026amp; Industrial Research (CSIR), Government of India is gratefully acknowledged. We acknowledge Prof. R. N. Mukherjee (former Prof, of IIT KANPUR and former director of IISER KOLKATA) and Prof. Tapas Kumar Sengupta (IISER KOLKATA) for their valuable suggestions and help.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ea) Elena Salvadeo, Lionel Dubois, Jean-Marc Latour. Coordination Chemistry Reviews. 2018, 374, 345\u0026ndash;375 b) Jingwen Chen, Xiaoyong Wang, Ying Shao, Jianhui Zhu, Yangguang Zhu, Yizhi Li, Qiang Xu, Zijian Guo, Inorg. Chem. 2007, 46, 8, 3306\u0026ndash;3312\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMar\u0026iacute;a R. Rodr\u0026iacute;guez, Mart\u0026iacute;n J. Lavecchia, Beatriz S. Parajon-Costa, Ana C. Gonzalez Baro, Mar\u0026iacute;a R. Gonzalez Baro, Elizabeth R. Cattaneo, Biochimie, 2021, 186, 43\u0026ndash;50\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS.Y. Yu, S.X. Wang, Q.H. Luo, L.F. Wang, Polyhedron 12 (1993) 1093\u0026ndash;1096.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eY. Li, J. Zhao, C.C. He, L. Zhang, S.R. Sun, G.C. Xu, J. Inorg. Biochem. 2015, 150, 28\u0026ndash;37\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eC.H. Ng, K.C. Kong, S.T. Von, P. Balraj, P. Jensen, E. Thirthagiri, H. Hamada, M. Chikira, Nucl. Acids Res. 2000, 28, 4856\u0026ndash;4864.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eP. Kumar, B. Baidya, S.K. Chaturvedi, R.H. Khan, B. Mondal, D. Manna, Inorg. Chim. Acta. 2011, 376, 264\u0026ndash;270\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eC. Metcalfe, J.A. Thomas, Chem. Soc. Rev. 2003, 32, 215\u0026ndash;224\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eK.E. Erkkila, D.T. Odom, J.K. Barton, Chem. Rev. 1999, 99, 2777\u0026ndash;2796\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM.A. Fuertes, C. Alonso, J.M. Perez, Chem. Rev. 2003, 103, 645\u0026ndash;662\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eY. Sun, S. Gou, R. Yin, P. Jiang, Eur. J. Med. Chem. 2011, 46, 5146\u0026ndash;5153\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eE.P. Swindell, P.L. Hankins, H. Chen, D.U. Miodragovic, T.V. O'Halloran, Inorg. Chem. 2013, 52, 12292\u0026ndash;12304\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eN. Cutillas, G.S. Yellol, C. de Haro, C. Vicente, V. Rodr\u0026iacute;guez, J. Ruiz, Coord. Chem. Rev. 2013, 257, 2784\u0026ndash;2797\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eR.A. Steiner, D. Foreman, H.X. Lin, B.K. Carney, K.M. Fox, L. Cassimeris, J.M. Tanski, L.A. Tyler, J. Inorg. Biochem. 2014, 137, 1\u0026ndash;11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKahn, O. Molecular Magnetism; VCH: New York, 1993.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSuh, M. P.; Han, M. Y.; Lee, J. H.; Min K. S.; Hyeon, C. J. Am. Chem. Soc. 1998, 120, 3819\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ. Suh, Acc. Chem. Res. 2003, 36, 562\u0026ndash;570.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA. Sreedhara, J.A. Cowan, J. Biol. Inorg. Chem. 2001, 6, 337\u0026ndash;347\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eF. Mancin, P. Scrimin, P. Tecilla, U. Tonellato, Chem. Commun. 2005, 2540\u0026ndash;2548.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. Brannum, A.K. Tipton, S. Zhu, L.J. Que, J. Am. Chem. Soc. 2001, 123, 1898\u0026ndash;1904\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eF. Medrano, A. Calderon, A.K. Yatsimirsky, Chem. Commun. 2003, 1968\u0026ndash;1970\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. Kathryn, T. Deck, A. Tseng, J.N. Burstyn, Inorg. Chem. 2002, 41 669\u0026ndash;677\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA. Sreedhara, J.D. Freed, J.A. Cowan, J. Am. Chem. Soc. 2000, 122, 8814\u0026ndash;8824\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eR. Ren, P. Yang, W.-J. Zheng, Z.-C. Hua, Inorg. Chem. 2000, 39, 5454\u0026ndash;5463\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eD. Montagner, V. Gandin, C. Marzano, A. Erxleben, J. Inorg. Biochem. 2015, 145, 101\u0026ndash;107\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eD. Gambino, Coord. Chem. Rev. 2011, 255, 2193\u0026ndash;2203\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eD. Crespy, K. Landfester, U.S. Schubert, A. Schiller, Chem. Commun. 2010, 46, 6651\u0026ndash;6662\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eB. Gyurcsik, A. Czene, Future Med. Chem. 2011, 3, 1935\u0026ndash;1962\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA. Meenongwa, R.F. Brissos, C. Soikum, P. Chaveerach, P. Gamez, Y. Trongpanich, New J. Chem. 2016, 40, 5861\u0026ndash;5876\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA. Tarushi, J. Kljun, I. Turel, A.A. Pantazaki, G. Psomas, D.P. Kessissoglou, New J.Chem. 2013, 37, 342\u0026ndash;355\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eG.R. Reddy, S. Balasubramanian, K. Chennakesavulu, J. Mater. Chem. A 2014, 2, 15598\u0026ndash;15610\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eN. Chitrapriya, J.H. Shin, I.H. Hwang, Y. Kim, C. Kim, S.K. Kim, RSC Adv. 2015, 5, 68067\u0026ndash;68075\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. Gonzalez, Alvarez, G. Alzuet, J. Borras, B. Macıas, and A. Castin eiras. Inorg. Chem. 2003, 42, 2992\u0026ndash;2998\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePratviel; G.; Bernadou; J.; Meunier, B. Angew. Chem., Int. Ed. Engl. 1995, 34, 746\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePogozelski, W. K.; Tullius, T. D. Chem. ReV. 1998, \u003cem\u003e98\u003c/em\u003e, 1089\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurrows, C. J.; Muller, J. G. Chem. ReV. 1998, \u003cem\u003e98\u003c/em\u003e, 1109\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJulian Heinricha, Niklas F. Koniga,b, Sebastian Sobottkaa, Biprajit Sarkara, Nora Kulaka, Journal of Inorganic Biochemistry, 2019, 194, 223\u0026ndash;232\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA.K. Das, A. De, P. Yadav, F. Lloret, R. Mukherjee, Polyhedron. 2019, 171, 365\u0026ndash;373\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ. Mukherjee, A. Sengupta, R. Mukherjee, Inorg. Chem. Acta. 2020, 513, 119899\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ. Mukherjee, R. Mukherjee, Dalton Trans. 2006, 1611\u0026thinsp;\u0026ndash;\u0026thinsp;1621\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYan An, Si-Dong Liu, Shu-Yi Deng, Liang-Nian Ji, Zong-Wan Mao Journal of Inorganic Biochemistry. 2006, 100, 1586\u0026ndash;1593\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSigman D. S.; Chen, C.-H. B. Chemical Nuclease Activity of 1,10- Phenantrolinecopper. In Metal-DNA Chemistry; Tullius, T. D., Ed.; ACS Symposium Series 402; American Chemical Society: Washington, DC, 1989; Chap. 2\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArup Kumar Das, Sukanta Mandal, Narottam Mukhopadhyay, Francesc Lloret and Rabindranath Mukherjee, ICA, 2025, 577, 122501.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eT.D. Smith, J.R. Pilbrow, Coord. Chem. Rev. 1974, 13, 173\u0026ndash;278\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eB.J. Hathaway, Copper, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehensive Coordination Chemistry, vol. 5, Pergamon, Oxford, 1987, pp. 533\u0026ndash;594.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"CuII complexes: trinuclear 1-benzyl-[3-(2'-pyridyl)] pyrazole as the terminal ligand, Gel electrophoresis, DNA cleavage","lastPublishedDoi":"10.21203/rs.3.rs-5698961/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5698961/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMetal ions and metal complexes are important components of nucleic acid biochemistry, participating both in the regulation of gene expression and as therapeutic agents. Cu(II) complexes are important for DNA cleavage, which is essential for the development of anticancer drugs and chemotherapeutic agents. For example, a study revealed that a Cu(II) complex caused double-strand DNA nicks, destabilized the DNA molecule, and disrupted the phosphodiester bonds. Here two trinuclear copper (II) complexes ware synthesized and structurally characterized: [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(\u003cstrong\u003eL\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2picolinate)\u003csub\u003e2\u003c/sub\u003e(OClO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e•2CH\u003csub\u003e3\u003c/sub\u003eCOCH\u003csub\u003e3\u003c/sub\u003e•2CH\u003csub\u003e3\u003c/sub\u003eOH (\u003cstrong\u003e1\u003c/strong\u003e) and [Cu\u003csup\u003eII\u003c/sup\u003e\u003csub\u003e3\u003c/sub\u003e(\u003cstrong\u003eL\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sup\u003e)\u003csub\u003e4\u003c/sub\u003e(2,6-dipicolinate)\u003csub\u003e2\u003c/sub\u003e] (ClO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e•6MeOH•2H\u003csub\u003e2\u003c/sub\u003eO (\u003cstrong\u003e2\u003c/strong\u003e) (\u003cstrong\u003eL\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sup\u003e = 1-benzyl-[3-(2'-pyridyl)] pyrazole; 2-picolinate = 2-pyridinecarboxylic acid; 2,6-dipicolinate = 2,6-pyridinedicarboxylic acid). The binding of copper complexes to plasmid DNA (P-DNA) has been investigated via UV-Visible spectroscopy, which revealed that P-DNA can covalently bind to the complexes. P-DNA cleavage was also investigated via agarose gel electrophoresis in the presence and absence of an oxidative agent (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e). The effect of the complex concentration on the P-DNA cleavage reaction has also been studied. Both copper complexes show nuclease activity, which significantly depends on the concentrations of the complexes, in the presence of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2,\u003c/sub\u003e likely through an oxidative mechanism whereas they slightly cleave P-DNA in the absence of an oxidative agent.\u003c/p\u003e","manuscriptTitle":"DNA cleavage activity of linear trinuclear copper(II) complexes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-15 09:35:46","doi":"10.21203/rs.3.rs-5698961/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"355f49df-6fbc-44dc-a439-2d58507b52c3","owner":[],"postedDate":"January 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-01-15T09:35:46+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-15 09:35:46","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5698961","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5698961","identity":"rs-5698961","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}