[Helix-coil transition in the simplest models of large native RNA. II. Consideration of nonspecific interactions]

A simple model of secondary structure of large native RNAs is proposed which makes allowance for the formation of week non-specific helices in addition to the formation of strong helices. It is shown that in this model, the same as in the one investigated earlier [1], cooperative melting of helices formed by interactions between remote parts of chain by the mechanism of the second order phase transition is observed upon changing the stability of helices.