Morio Yashiro

Conjugates of a Dinuclear Zinc(II) Complex and DNA Oligomers as Novel Sequence‐Selective Artificial Ribonucleases

Even in the presence of a large excess of ZnII ions, sequence-selective RNA hydrolysis is achieved by DNA conjugates involving a dinuclear ZnII complex (shown schematically). This is because the cooperation of two ZnII ions is essential for the RNA scission.

Metal-ion-assisted hydrolysis of dipeptides involving a serine residue in a neutral aqueous solution

Dipeptides having a serine residue at the C-terminus, X-Ser, where X is an appropriate amino acid residue, were efficiently hydrolyzed in the presence of ZnCl2 at pH 7.0. The rapid hydrolysis of X-Ser is due to an autocatalysis of the hydroxy group in the serine residue, and is found to be accelerated by a metal ion, in particular by ZnCl2. Roles of the metal ion in the hydrolysis of peptides involving a serine residue, in relation to the recently reported protein cleavages, are discussed.

Remarkably fast hydrolysis of 3′,5′-cyclic adenosine monophosphate by cerium(III) hydroxide cluster

Cerium(III) hydroxide cluster hydrolyses 3′,5′-cyclic adenosine monophosphate at an unprecedentedly large rate (half-life 35 s at pH 8.0; 30°C).

Cerium(IV)–cyclodextrin complex for peptide hydrolysis in neutral homogeneous solutions

Di- and tri-peptides are efficiently hydrolysed by the cerium(IV)–γ-cyclodextrin complex in neutral and homogeneous solutions.

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.

Efficient and unique cooperation of three zinc(ii) ions in the hydrolysis of diribonucleotides by a trinuclear zinc(ii) complex

A trinuclear Zn 2+ complex is prepared using a ligand having six pyridine moieties, N,N,N′,N′,N″,N″ -hexakis(2-pyridylmethyl)[tris(2-aminoethyl)amine] (L 3 ), and efficiently hydrolyses diribonucleotides at pH 7 and 50 °C, showing much greater activity than a dinuclear Zn 2 L 2 complex.

Solubilization of lanthanide ions by cyclodextrins in basic aqueous solutions

Cyclodextrins form complexes with lanthanide ions in basic aqueous solutions. This complex formation in basic solution dramatically enhances the solubility of lanthanide ions, which are otherwise insoluble due to the formation of hydroxide gels. Solutions of the γ-cyclodextrin-Ce3+ complex effectively hydrolyze 2′-deoxyadenosine-5′-monophosphate to 2′-deoxyadenosine.

Lanthanide ion-induced hydrolyses of alkyl esters and amides of α-amino acids†

Lanthanide ion-induced hydrolyses of methyl esters, ethyl esters, and amides of α-amino acids were systematically studied. In the hydrolysis of the alkyl esters, all the lanthanide ions are effective and the catalytic activities decrease in the order Ce(III), Nd(III) > Sm(III) > Eu(III) > Gd(III), Ce(IV) > Pr(III) > Dy(III), Tb(III), Er(III), Ho(III), Tm(III) > La(III), Lu(III), Yb(III). For the hydrolysis of the amides, however, the Ce(IV) ion is overwhelmingly more active than other lanthanide(III) and non-lanthanide ions. The results are interpreted in terms of the difference in the rate-limiting step for these two reactions.