The dipolar and exchange contributions to the spin-lattice relaxation of the imino protons in poly(rA)*poly(rU).
01 January 1987
Selective, semiselective, and biselective excitation has been used to study the spin-lattice relaxation of the hydrogen bonded imino protons in the sonicated, double-stranded RNA polymer poly(rA)*poly(rU). The spin-lattice relaxation of the imino protons has contributions from both dipolar interactions and exchange with the solvent and the relative contribution of each to the observed rate depends on temperature. When exchange is slow compared to the dipolar contribution, the two components can be resolved by measuring the relaxation rate with and without prior inversion of the solvent peak. When exchange is fast, the contributions can be resolved by comparing the initial selective relaxation rate with the rate of saturation transfer when the solvent peak is inverted. This allows the exchange and dipolar contributions to be separated at temperatures well below the duplex melting temperatures and provides an easy way to study the mechanism of proton exchange with the solvent.