where A is the absorbance value at a given temperature T, A H is the absorbance of the fully helical ssRNA, A C is the absorbance of the fully random coil ssRNA, ÁS and ÁH are the entropy and enthalpy of the melting transition respectively, and R is the gas constant (37, 38) . Absorbance values were fitted to the above equation using the non-linear least squares fitting function in Origin 7 to determine thermodynamic parameters. The melting temperature (T m ) was determined by dividing the enthalpy by the entropy.