Combined theoretical and experimental investigation of a DNA interactive poly-hydroxyl enamine tautomer exhibiting turn on sensing for Zn2+ in pseudo-aqueous medium


Crystallographically established (solid state structure at 150 K temperature) enamine ligand 2-((1,3-dihydroxy-2-(hydroxymethyppropan-2-ylamino)methyl)-4-bromo-6-methoxyphenol (H4L) was prepared, which showed interconvertible equilibrium (Delta E = 7.37 kcal) of its tautomers and also found to exhibit DNA binding activity at the minor groove of double-stranded (ds) DNA. Spectroscopic and calorimetric methods were employed to explore the interaction of H4L with DNA. Further, the competitive Hoechst 33258 displacement assay indicated the specific binding site of H4L to be at the minor grooves of DNA. Thermodynamic evaluation from isothermal titration calorimetry (ITC) experiments suggested the association of H4L with DNA to be an enthalpy driven process with an equilibrium binding affinity (K) of (2.50 +/- 0.11) x 10(4) M-1. Molecular docking studies were found to be in good agreement with the experimental results of the DNA interaction of the probe in groove binding mode. The poor emission of H4L in the excited state was due to excited state induced proton transfer (ESIPT), but in the presence of Zn2+, the ESIPT was blocked an chelation-enhanced fluorescence (CHEF) was initiated to exhibit 'turn on' fluorescence upon the coordination of Zn2+. The H4L probe was found to detect Zn2+ selectively among various metal ions and the LOD was calculated to be similar to 1.13 mu M. The coordination of the Zn(II) bound complex and the relative stability of the tautomers of H4L were investigated in detail via spectroscopic and computational studies.



subject category

Chemistry, Multidisciplinary


Saha, U; Mabhai, S; Das, B; Kumar, GS; Brandao, P; Dolai, M

our authors


MD acknowledges Science & Engineering Research Board (SERB), Govt. of India (ref. No. PDF/2016/000334) and US is thankful to the University Grants Commission (Government of India) for providing D.S. Kothari Postdoctoral Fellowship (DSKPDF Ref. No. F.4-2/2006 (BSR)/CH/17-18/0236). Pradip Bera, Kandi Raj College, Murshidabad, India is acknowledged for his cooperation and valuable suggestion toward this work. Mr Sandip Kundu, CSIR-IICB, Kolkata, W.B., India is also acknowledged for the instrumental support.

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