Hydrolytic activity of a crown ether-lanthanum complex in the phosphate diester and DNA cleavage

Abstract

This study mainly reported the catalytic activity, the catalytic trend and the catalytic mechanism of a crown ether-lanthanum complex in the phosphoester and the DNA hydrolysis. The catalytic capacity of the lanthanum complexes was investigated under different pH and the concentrations. The rate of the phosphoester hydrolysis was measured kinetically with Uv-vis spectrophotometric method, and the first-order rate constant k_cat for the phosphoester catalytic hydrolysis was obtained through a double-reciprocal method. The results indicated that the title complex exhibited relatively high catalytic function, and the reaction rate of the phosphoester catalytic hydrolysis was about 10⁸ -fold faster than that of its spontaneous hydrolysis. A pH-dependence of the reaction rate indicated that the active species as real catalyst come from the deprotonation of the water-coordinated molecules in the complex. The pUC19 DNA cleavage was completed by the gel electrophoresis. The results showed that the title complex can accelerated the breakage of supercoiled DNA at the almost physiological conditions, and both DNA and the phosphoester catalytic hydrolysis followed the same qualitative trends, and the supercoiled DNA (form I)was thoroughly cleaved to the nicked form (form II) under the appropriate conditions.