Efficient RNA hydrolysis by lanthanide(III)–hydrogen peroxide combinations. Novel aggregates as the catalytic species1

Abstract

Combinations of lanthanum(III) ion and hydrogen peroxide efficiently hydrolyze RNA under physiological conditions, because of a synergetic cooperation. The rate constant for the hydrolysis of adenylyl(3′-5′)adenosine at pH 7.2 and 30 °C is 7.7 × 10^–2 min^–1, when [La^III]₀ = 10 and [H₂O₂]₀ = 100 mM. This value is 460 times as great as that for the ApA hydrolysis by La^III alone (1.7 × 10^–4 min^–1). Hydrogen peroxide is inactive when used separately. A similar synergism operates between Nd^III and H₂O₂. According to the kinetic analysis and the potentiometric titration, a trimeric aggregate of [La(O–O)₃La] complex is responsible for the RNA hydrolysis. This result is in contrast with the previous proposal on the hydrolysis of bis(4-nitrophenyl)phosphate that monomeric species of [La(O–O)₂La]²⁺ is the active species (B. K. Takasaki and J. Chin, J. Am. Chem. Soc., 1995, 117, 8582). The discrepancy is ascribed to the difference in the basicities of the leaving groups in the substrates.