To further our investigation of this model NMR construct, we completed non-exchangeable NMR experiments, including C-1 H heteronuclear single quantum coherence spectroscopy (HSQC), H-1 H 2D NOESY, and double quantum filtered correlation spectroscopy (DFQ COSY) experiments (Figure ), which are not limited by solvent exchange associated with imino proton experiments . These experiments also revealed extensive broadening due to exchange with nucleotides within and neighboring of the 2×2 internal loop, broadening beyond detection.