Improved free energies for G · C base-pairs☆

Abstract Thermodynamic parameters of helix formation are reported for seven oligoribonucleotides containing only G · C pairs. These data are used with the nearest-neighbor model to calculate enthalpies and free energies of base-pair formation for G · C pairs. For helix initiation, the free energy change at 37 °C, ΔG 37 0 , is + 3.9 kcal/mol; for helix propagation, the ΔG 37 0 values are −2.3, −3.2 and −3.3 kcal/mol for C-G, G-G and G-C neighbors, respectively.