Preparation of Artificial nuclease and creation of new-biotechnology

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Non-enzymatic hydrolysis of DNA has been one of the most significant targets for chemists. Several years ago, the remarkable catalysis by the lanthanide ions was found, and highly stable phosphodiester linkages in DNA were hydrolyzed at pH 7. The Ce (IV) ion is especially active. However, the Ce (IV) easily forms a gel of metal hydroxide, and this feature imposes limitations to the scope of its application. Homogeneous and catalytically active Ce (IV) complexes are required for more versatile applications. In this research, we fourcused on the development of (1) catalytically active Ce (IV) complexes, and (2) the methods of the activation of the target phosphodiesters in nucleic acids.(1) Homogeneous Ce (IV) complex of EDTA promptly hydrolyzes oligonucleotides under physiological conditions. In contrast, dinucleotides are not hydrolyzed to measurable extents. The degree of polymerization of DNA substrate is crucial for the present catalysis. The activity of this complex is significantly increased by the cooperation with selected oligoamines. The reaction in the presence of spermine (10 μmol dm^<-3>) is about 5O times as fast as that in its absence.(2) Non-covalent systems (ternary system), composed of (i) DNA oligomer bearing an acridine, (ii) unmodified DNA, and (iii) free lanthanide (III) ion, selectively and efficiently hydrolyse RNA at the target pohosphodiester. The corresponding phosphodiester linkage is notably activated by non-covalent interactions with the DNAs ((i) and (ii)), and thus the site-selective scission by the metal ion promptly proceeds under physiological conditions. The sequence-selective RNA scission is also achieved by non-covalent combinations of lanthanide (III) ion and one DNA bearing an acridine in its intern al position (binary system). The target phosphodiester linkage is also activated by the modified DNA, and preferentially hydrolyzed. The DNA-Acr/Lu (III) binary system is still more (about 20%) active than the ternary system.