Binding, Electrochemical Activation, and Cleavage of DNA by Cobalt(II) Tetrakis-<i>N</i>-methylpyridyl Porphyrin and Its β-Pyrrole Brominated Derivative Shivaraj Yellappa Jaldappagari Seetharamappa Lisa M. Rogers Raghu Chitta Ram P. Singhal Francis D'Souza 10.1021/bc060153x.s001 https://acs.figshare.com/articles/journal_contribution/Binding_Electrochemical_Activation_and_Cleavage_of_DNA_by_Cobalt_II_Tetrakis_i_N_i_methylpyridyl_Porphyrin_and_Its_Pyrrole_Brominated_Derivative/3047482 The binding of nucleic acids by water-soluble cobalt(II) tetrakis-<i>N</i>-methylpyridyl porphyrin, (TMPyP)Co, and its highly electron-deficient derivative cobalt(II) tetrakis-<i>N</i>-methyl pyridyl-β-octabromoporphyrin, (Br<sub>8</sub>TMPyP)Co, was investigated by UV−visible absorption, circular dichroism (CD), and electrochemical and gel electrophoresis methods. The changes of the absorption spectra during the titration of these complexes with polynucleotides revealed a shift in the absorption maxima and a hypochromicity of the porphyrin Soret bands. The intrinsic binding constants were found to be in the range of 10<sup>5</sup>−10<sup>6</sup> M<sup>-1</sup>. These values were higher for the more electron-deficient (Br<sub>8</sub>TMPyP)Co. Induced CD bands were noticed in the Soret region of the complexes due to the interaction of these complexes with different polynucleotides, and an analysis of the CD spectra supported a mainly external mode of binding. Electrochemical studies revealed the cleavage of polynucleotides by (TMPyP)Co and (Br<sub>8</sub>TMPyP)Co in the presence of oxygen preferentially at the A−T base pair region. Gel electrophoresis experiments further supported the cleavage of nucleic acids. The results indicate that the β-pyrrole brominated porphyrin, (Br<sub>8</sub>TMPyP)Co, binds strongly and cleaves nucleic acids efficiently as compared with (TMPyP)Co. This electrolytic procedure offers a unique tool in biotechnology for cleaving double-stranded DNA with specificity at the A−T regions. 2006-11-15 00:00:00 porphyrin Soret bands cobalt Br 8TMPyP Induced CD bands absorption gel electrophoresis methods Electrochemical cleavage acid region UV Br 8TMPyP gel electrophoresis experiments DNA binding complex spectra polynucleotide