title: A self-cleaving DNA enzyme modified with amines, guanidines and imidazoles operates independently of divalent metal cations (M2+).
abstract: The selection of modified DNAzymes represents an important endeavor in expanding the chemical and catalytic properties of catalytic nucleic acids. Few examples of such exist and to date, there is no example where three different modified bases have been simultaneously incorporated for catalytic activity. Herein, dCTP, dATP and dUTP bearing, respectively, a cationic amine, an imidazole and a cationic guanidine, were enzymatically polymerized on a DNA template for the selection of a highly functionalized DNAzyme, called DNAzyme 9-86, that catalyzed (M(2+))-independent self-cleavage under physiological conditions at a single ribo(cytosine)phosphodiester linkage with a rate constant of (0.134 +/- 0.026) min(-1). A pH rate profile analysis revealed pK(a)'s of 7.4 and 8.1, consistent with both general acid and base catalysis. The presence of guanidinium cations permits cleavage at significantly higher temperatures than previously observed for DNAzymes with only amines and imidazoles. Qualitatively, DNAzyme 9-86 presents an unprecedented ensemble of synthetic functionalities while quantitatively it expresses one of the highest reported values for any self-cleaving nucleic acid when investigated under M(2+)-free conditions at 37 degrees C.
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver BC, V6T 1Z1, Canada.
authors.forename: Marcel
authors.initials: M
authors.lastname: Hollenstein
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hipolito
authors.forename: Curtis H
authors.initials: CH
authors.lastname: Lam
authors.forename: David M
authors.initials: DM
authors.lastname: Perrin
mesh_terms: D000588:Amines / Q000737:chemistry*; D001483:Base Sequence; D002413:Cations, Divalent / Q000737:chemistry; D004247:DNA / Q000378:metabolism; D021881:DNA, Catalytic / Q000737:chemistry* / Q000378:metabolism; D003838:Deoxyadenine Nucleotides / Q000737:chemistry; D003845:Deoxycytosine Nucleotides / Q000737:chemistry; D003856:Deoxyuracil Nucleotides / Q000737:chemistry; D006146:Guanidines / Q000138:chemical synthesis / Q000737:chemistry*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry*; D007700:Kinetics; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D012313:RNA / Q000378:metabolism; D013696:Temperature
chemical_list: D000588:Amines; D002413:Cations, Divalent; D021881:DNA, Catalytic; D003838:Deoxyadenine Nucleotides; D003845:Deoxycytosine Nucleotides; D003856:Deoxyuracil Nucleotides; D006146:Guanidines; D007093:Imidazoles; D012313:RNA; D006160:Guanosine Triphosphate; D004247:DNA