Spectroscopic study on the interaction of ct-DNA with manganese Salen complex containing triphenyl phosphonium groups

The DNA binding properties of a bulky and hydrophobic Schiff base complex of manganese(III) [N,N′-bis(5-(triphenyl phosphonium methyl)salicylidene)-1,2-ethylene diamine chloride Mn(III) acetate] was examined by spectroscopic techniques. UV–vis titration data indicate both hypo and hyperchromic effect with addition of DNA to complex. A competitive binding study showed that the enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by adding Mn Salen complex. This finding indicates that Mn Salen complex displaces EB from its binding site in DNA. Helix melting studies indicate improvement in the helix stability, and an increase in the melting temperature. The analysis of CD spectra represents the structural changes in DNA due to the binding of Mn Salen complex. The binding constant has been calculated using absorbance and fluorescence data. The results also represent that the binding process proceeds by strong electrostatic and hydrophobic interactions.

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► Mn Salen complex interacts with DNA.
► The Scatchard plots shows that type B and D are dominating in the system.
► Thermal plot shows two phase transition after adding Mn Salen to the DNA.
► An induced CD shows that the electronic transition moment of Mn Salen is directed along a groove of the DNA.