Experimental and Computational Evidence on the Interaction of Cycloalkyl α-Aminobisphosphonates with Calf Thymus DNA

Fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, circular dichroism spectroscopy, viscometry, cyclic voltammetry, and differential pulse voltammetry were applied to investigate the competitive interaction of DNA with the three new cycloalkyl α-aminobisphosphonates (D₁-D₃) and spectroscopic probe, neutral red dye, and Hoechst (HO), in a Tris-hydrogen chloride buffer (pH 7.4). The spectroscopic and voltammetric studies showed that the groove binding mode of interaction is predominant in the solution containing DNA and α-aminobisphosphonates. Furthermore, the results indicated that α-aminobisphosphonate with the lengthy N alkyl chains and larger heterocyclic ring size had a stronger interaction. The principal component analysis and theoretical quantum mechanical and molecular mechanics (QM-DFT B3LYP/6-31+G* and MM-SYBYL) methods were also applied to determine the number of chemical components presented in complexation equilibrium and identify the structure complexes of DNA with the three new cycloalkyl α-aminobisphosphonates (D₁-D₃), respectively.