Abstract
The cleavage of the RNA dimers GpA and ApUp is promoted by the inert cobalt(III) complex [Co(tren)(OH 2 )(OH)] 2+ (tren= N , N -bis(2-aminoethyl)ethane-1,2-diamine) the reactions being followed spectrophotometrically, with rate enhancements comparable to those observed for that complex reacting with the model phosphodiester bis( p -nitrophenyl)phosphate. Likewise, the labile [Cu(tach)(OH 2 )(OH)] + complex (tach=cyclohexane-1,3,5-triamine) promotes cleavage of the RNA dimer ApA and trimer ApCpC, observed using electrospray ionization mass spectrometry (ESIMS). Mixtures of ApCpC or ApA and the copper complex prepared at room temperature and examined immediately exhibit peaks assigned to the phosphodiesters and their copper complexes. After heating at elevated temperature for several hours, the ESIMS show clear evidence of cleavage, with peaks due to the parent phosphodiester and their initial complexes absent. While the metal complex promotes the reaction, cyclic phosphodiester intermediates observed also support a trans-esterification cleavage mechanism with a key role for the 2'-OH group on the ribose unit as well as promotion of reaction by metal ion complexation.