Self cleavage of C8-histamino-r (UpA) promoted by ZnCl₂: mechanistic studies on a designed ribonuclease mimic

Abstract

Studies on self cleavage of dinucleotides (2-5) containing conjugated imidazole and ethylenediamine chains indicated that the imidazole conjugated ribodinucleotide 4 hydrolyzed in presence of ZnCl₂, whereas other dinucleotides 2, 3 and 5 were inert. An acceleration of 10-15 times in rate of hydrolysis of 4 was observed as compared to the unmodified dinucleotide 6. The product analysis by HPLC suggested that the reaction involves cleavage of P-O5' bond with the formation of C8-histamino dA 9 and 2',3'-cUMP 10 which subsequently hydrolyzed to a mixture of 2' and 3' UMP by a slower reaction. The mechanism of hydrolysis of designed model compound 4 is similar to that of the first step of hydrolysis of RNA by RNase A.