Tetsuro Shiiba

Lanthanide metal complexes for the hydrolysis of linear DNAs

Abstract Lanthanum (III) and cerium (III) complexes of macrocyclic ligands efficiently hydrolyze the phosphodiester linkages in linear DNAs at pH 7.2 and 30–50°C. Both single-stranded and double-stranded DNAs are hydrolysed without specific base preference, yielding predominantly 3′-phosphate termini. The potential of these complexes as the catalytic centers of artificial hydrolytic nucleases are indicated.

Rare Earth Metal Ions for DNA Hydrolyses and Their Use to Artificial Nuclease1

Abstract Phosphodiester linkages in linear DNAs are efficiently hydrolyzed by rare earth metal salts. The activities of CeCl3 and Ce(NH4)2(NO3)6 are especially large. Artificial hydrolytic nuclease for highly selective scission of DNA has been prepared by the attachment of Ce(IV) ion to a DNA oligomer as a sequence recognizing moiety.

Efficient and oxygen-independent hydrolysis of single-stranded DNA by cerium(IV) ion

Cerium(IV) ion efficiently hydrolyses the phosphodiester linkages in DNAs, even in the absence of molecular oxygen. The pseudo first-order rate constant for the hydrolysis of thymidylyl(3′,5′)thymidine (TpT) by Ce(NH4)2(NO3)6(0.01 mol dm–3) at pH 7 and 50 °C is 1.9 × 10–1 h–1(the half-life is 3.6 h), either with or without molecular oxygen. DNA hydrolysis by CeCl3 requires molecular oxygen to convert the CeIII ion to CeIV. Addition of hydrogen peroxide causes various side-reactions rather than accelerating the hydrolysis. The hydrolysis by CeIV proceeds via P–O scission, as confirmed by the absence of 18O incorporation into thymidine (T) during the reaction in an H218O–H216O mixture. There exists no specific base-preference in the scission, and concurrent oxidative cleavage of the deoxyribose is nil. The activity of CeIV is more than 200 fold greater than those of trivalent lanthanide ions and of other tetravalent ions. A significant D2O solvent isotope effect and the pH independence of the hydrolysis rate indicate that the hydrolysis proceeds via an intramolecular attack by the CeIV-bound hydroxide ion and that the reaction is further assisted by the general acid catalysis of another water bound to the CeIV ion.

Phenyl ester of adenosine 3′-Phosphate as a novel probe for the rate-limiting step in RNA hydrolysis

Abstract Phenyl ester of adenosine 3′-phosphate is synthesized as a probe for the rate-limiting steps in enzymatic and non-enzymatic RNA hydrolyses.