Effect of ancillary ligand on DNA and protein interaction of the two Zn (II) and Co (III) complexes: experimental and theoretical study

Abstract

In the present work we have developed one mononuclear Zn(II) complex [Zn(L)(H2O)] (Complex 1) by utilizing a tetracoordinated ligand H₂L, formed by simple condensation of 2, 2 dimethyl 1,3 diamino propane and 3- ethoxy salicylaldehyde and one newly designed mononuclear Co (III) complex [Co(L)(L1)] (complex 2) by utilizing (H₂L) and 3- ethoxy salicylaldehyde(HL1) as an ancillary ligand. The newly developed complex 2 have been spectroscopically characterized. An interesting phenomenon has been noticed that in presence of ancillary ligand, the solubility in buffer solution and the thermal stability of complex 2 comparatively increases than 1. To check the effect of ancillary ligand, present in complex 2 towards the DNA and HSA binding efficacy, both the complexes have been taken into consideration to inspect their binding potentiality with the macromolecules. The ‘on’, ‘off’ fluorescence changes in presence of DNA and HSA, the binding constant values, obtained from electronic spectral titration, iodide induced quenching, competitive binding assay, circular dichroism (CD) spectral titration, time resolved fluorescence experiment unambiguously assure the better binding efficacy of complex 2 with the signal of minor groove binding mode with DNA along with no significant conformational changes of the macromolecules. The strong and spontaneous binding of complex 2 with CT-DNA is further supported by the Isothermal Titration Calorimetry (ITC) study. Furthermore TDDFT calculation of DNA with and without complex 2 significantly authorize the formation of complex 2-DNA adduct during the association. Finally Molecular Docking study properly verifies the experimental findings and provides justified explanation behinds experimental findings.

Graphical abstract

Communicated by Ramaswamy H. Sarma

Keywords:

• Metal complex
• DNA/HSA
• interaction
• fluorescence spectroscopy
• CD spectroscopy
• molecular docking

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors are very much grateful to the ‘Science and Technology Biotechnology Government of West Bengal’ for financial support through the scheme Gabesanay Bangla. Dr. Tithi Maity (T.M.) has also acknowledged DFT FIST for their financial support to Prabhat Kumar College, Contai. Dr. Maity has paid her deep gratitude to the college authority for continuous support to the entire period of work. The author also would like to express deep gratitude to Prof. Debasis Das, and Miss Somali Mukherjee, Department of Chemistry, University of Calcutta for their valuable scientific suggestion. Author SSM gratefully acknowledge SERB for grant in project (Project Number TAR/2019/000030).