Heteronuclear NMR spectroscopy has been used to probe the structure and dynamics of a lead-dependent ribozyme known as the leadzyme. The pK(a)’s for all adenine bases in the leadzyme were measured and vary from <3.1 to 6.5. The adenines with the lowest pK(a)’s are involved in Watson-Crick base pairs, and the adenine with the highest pK(a) is thought to form an AH(+)-C wobble base pair at the active site of the leadzyme. The potential structural and functional significance associated with perturbed pK(a)’s in ribozymes is discussed. NMR studies of 5’ AMP, 5’ CMP, 5’ GMP, and 5’ UMP were also used to identify the C-13 resonances that represent the best probes of base protonation for all four bases in RNA. The line width of the C2 resonance of the adenine with a pK(a) of 6.5 was analyzed to probe the dynamics of the catalytically active internal loop in the leadzyme. These results showed that this adenine is undergoing a chemical exchange process with a lifetime of similar to 30 mu s and demonstrate rapid dynamics at the active site of this ribozyme. Thus C-13 NMR can be used to probe dynamic processes in RNA oligomers.