Quantitative study of As (V) and As (III) interaction with mangrove DNA by molecular fluorescence spectroscopy

This study describes the in vitro study of (1:1) one step nucleophilic displacement ([Formula: see text]) of phosphate by heavier anion arsenate and arsenite in the DNA of arsenic ridden Sundarban mangroves. Mangrove DNA was found to give rise to a broad fluorescence and its integrated fluorescence intensity was enhanced on addition of As (V) and As (III), respectively. Analyses of the fluorescence parameter showed adequacy of 1:1 model to describe substitution of phosphate of mangrove DNA chain exiplex by arsenate and arsenite with equilibrium constant (log Kc) ranging between 4.19 and 4.32 for As (V), and between 3.77 and 3.89 for As (III) at pH 7 and 25°C. In the cases, the melting temperature (Tm) and reassociation rate constant of mangrove DNA was increased on treatment with As (V) and As (III). It is suggested that heavier ion arsenate and arsenite may substitute phosphate in natural DNA.