Relaxation kinetics of the helix-coil transition of a self-complementary ribo-oligonucleotide: A7U7.

Relaxation measurements on the kinetics of the double helix to coil transition for the self-complementary ribo-oligonucleotide A7U7 are reported over a concentration range of 6.9 micrometer to 19.6 micrometer in single strand in 1 M NaCl. The rate constants for helix formation are about 2 X 10(6) M-1 s-1 and decrease with increasing temperature yielding an activation enthalpy of -6 kcal/mole. The rate constants for helix dissociation range from 3 to 250 s-1 and increase with increasing temperature yielding an activation enthalpy of +45 kcal/mole. The kinetic data reported here for 1 M NaCl is compared with previously published results obtained at lower salt concentrations. These data are discussed in terms of the quantitative effect of ionic strength on the kinetics of helix-coil transitions in oligo- and polynucleotides.