RNA folds into 2D structures through Watson-Crick base pairing (A-U, G-C) and wobble pairs (G-U). The minimum free energy structure determines function.
Base pairs:
A-U (2 H-bonds) · G-C (3 H-bonds) · G-U wobble
Each base pair contributes ~-2 to -3 kcal/mol. Loops and bulges destabilize. The minimum free energy structure is found by dynamic programming (Nussinov algorithm).