Energy Landscape of The TPP Riboswitch.A: Tertiary structure of an E. coli TPP (or thi-box) riboswitch bound to thiamine pyrophosphate . The image was generated by the Jmol from the PDB:2hoj structure taken from the Rfam website . B: Ligand-bound and unbound secondary structures of a TPP riboswitch in B. subtilis, taken from . C: Energy landscape of the B. subtilis riboswitch taken from . Set-1 and Set-2 clusters correspond to the two mutually exclusive secondary structures of the TPP riboswitch. Pairwise Base-pairing distance used as a measure of distance between two structures. Please refer to  for detailed information about the figure and clustering details.