THE ASSOCIATION OF COMPLEMENTARY RIBONUCLEIC-ACIDS CAN BE STRONGLY INCREASED WITHOUT LOWERING ARRHENIUS ACTIVATION-ENERGIES OR SIGNIFICANTLY ALTERING STRUCTURES

The association rates of complementary nucleic acids can be increased by 2-3 orders of magnitude in vitro by cellular proteins and low molec ular weight compounds including cetyltrimethylammonium bromide (CTAB). In this work, we provide experimental evidence that the CTAB-mediated enhancement of RNA-RNA annealing by approximately 3 orders of magnitu de is due to a favorable activation entropy (Delta S double dagger) an d not due to a decrease of the Arrhenius activation energy (E-a) nor t o major structural changes of the RNA. Two alternative models for the CTAB-facilitated RNA-RNA annealing will be discussed. First, CTAB coul d form a positively charged liquid matrix which could steer complement ary RNA molecules and thereby increase their collision frequency and a nnealing rate. Second, increased annealing rates could be explained by stabilization of a non-base-specific precomplex of both complementary RNA molecules in solution.