An ionic liquid form of DNA: Redox-active molten salts of nucleic acids

Ionic liquids are described that contain duplex DNA as the anion and polyet her-decorated transition metal complexes based on M(MePEG-bpy)(3)(2+) as th e cation (M = Fe, Co; MePEG-bpy = 4,4'-(CH3(OCH2CH2)(7)OCO)(2)-2,2'-bipyrid ine). When the undiluted liquid DNA-or molten salt-is interrogated electroc hemically by a microelectrode, the molten salts exhibit cyclic voltammogram s due to the physical diffusion (D-PHYS) Of the polyether-transition metal complex. When M = Co(II), the cyclic voltammogram of the melt shows an oxid ative wave due to the co(mm) couple at E-1/2 = 0 40 V (versus Ag/AgCl) and a DPHYS Of 6 x 10(-12) cm(2)/s, which is significantly lower than that for Co(MePEG-bpy)(3)(ClO4)(2) (D-PHYS = 2.6 x 10(-10) cm(2)/s) due to greater v iscosity provoked by the DNA polymer. When a 1:1 mixture is made of the Co( MePEG-bpy)(3). DNA and Fe(MePEG-bpy)(3)(ClO4)(2) melts, two redox waves are observed. The first is due to the Co(III/II) couple, and the second is a c atalytic wave due to oxidation of guanine in DNA by electrogenerated Fe(III ) in the undiluted melt. Independent experiments show that the Fe(III) form of the complex selectively oxidizes guanine in duplex DNA. These DNA molte n salts constitute a new class of materials whose properties can be control led by nucleic acid sequence and that can be interrogated in undiluted form on microelectrode arrays.