Characterization of the G-Quadruplex Structure of a Catalytic DNA with Peroxidase Activity

It has been reported that the complexes formed by hem in and some G-quadruplexes can be developed as a new class of DNAzyme with peroxidase activity. This kind of DNAzyme has received a great deal of attention. But to date, the actual G-quadruplex structure that can provide hemin with enhanced peroxidase activity is in doubt. Herein, the G-quadruplex structure of CatG4, a 21-nucleotide DNA oligomer which was previously reported to bind hemin and the resulting complex exhibiting enhanced peroxidase activity, was characterized by fluorescence and circular dichroism measurements. The results suggest that the catalytically active form of of CatG4 may be a unimolecular parallel quadruplex rather than a unimolecular chair-type antiparallel quadruplex or a multistranded parallel quadruplex In addition, the fluorescence analysis of labeled oligonucleotides may be developed as a supplementary tool for the study of DNA conformations. (C) 2009 Wiley Periodicals, Inc. Biopolymers 91: 331-339, 2009.