Study of the G-quadruplex Forming Peroxidase-like DNAzyme by Spectroscopy Methods

DNA molecules contain nitrogenous bases that look like fluorophores; however they are weakly or non-fluorescent. Hence، it is important to identify DNA binding-ligands that do not show fluorescence emission in the Free State، though their fluorescence intensity increases upon binding to DNA. Here،we report metal ions (either K and Na) induced guanine quadruplex formation with PS2. M، d (GTG3TAG3CG3T2G2)، which shows peroxidase function when complexed with hemin. Ultravioletvisible absorption spectroscopy revealed activity of the PS2. M oligomer as DNAzyme، and Circular Dichroism spectroscopy showed the formation of G-quadruplex structure of PS2. M. We also studied the intrinsic fluorescence of G-quadruplex forming peroxidase-like DNAzyme. The fluorescence spectra showed increment in the intrinsic fluorescence of folded DNA in comparison with its unfolded structure of the same sequence. Moreover، unsymmetrical cyanine dye (SYBR gold) was utilized as a probe for the study of the extrinsic fluorescence of G-quadruplex DNA، where it could discriminate between the single and four-stranded structures of DNA. Also the G-quadruplex dye interaction was also investigated using Circular Dichroism and Fluorescence spectroscopies.