For an example protein 1TQG, the plots show how the initial O-N distances for a SB forming residue pair may exist in a closed (formed) or open (broken) configurations in the ensemble. The figures indicate a) O-N distance of GLU32 and LYS79 in ITQG in the in vacuo EM structure, b) GBIS EM structure, c) The O-N distance observed in the MD generated ensemble (horizontal broken lines indicate the corresponding distance in vacuo EM and GBIS EM structures, respectively), d) the distribution of the O-N distance in MD generated ensemble (vertical broken lines indicate the corresponding distance in vacuo EM and GBIS EM structures, respectively).