Nucleoside-copper(II) system in water and on 13X-zeolite studied by continuous-wave and pulsed-wave ESR

Abstract

In order to study the effects of large-surface-area solids on the formation of biomacromolecules, copper(II)-nucleosides complexes were studied in water at high pH and after contact with the cavity walls of 13X-zeolite. The results were mainly colIected by electron spin resonance in continuous (cw-ESR) and pulsed (ESE) wave. Particular attention was dedicated to adenosine as a nucleoside model for the formation of compounds which were fully characterized in alkaline water solution and after adsorption on commercial 13X-zeolite. In aqueous solution, adenosine was coordinated to copper(II) through deprotonated hydroxyl groups in the 2' and 3' positions of the ribose unit, with the formation of lCu(adenosine)z(HzO)2] 2-. When adsorbed on zeolite, both cw-ESR and ESE showed that a fraetion of the adsorbed complexes did not change their structure and showed high mobility in the zeolite faujasite cavity. The remaining fraction directly interacted with 27A1 nuclei of the zeolite framework. Other copper(lI)-nucleosides behaved in the same manner. Surprisingly enough, alkaline solutions of nuc[eos~des were able to remove copper([l) from zeolite in the forro of [Cu(adenosine)2(H20)2] 2-which free[y moved in the supematant aqueous liquid.