TOF-TOF data of the Cx43 peaks at m/z 1716.84 and m/z 1748.91. The peptides 1716.84 (upper) and 1748.91 (lower) are from rat and Chinese hamster Cx43, respectively. Note that the y2-ion at m/z 303.2 had higher intensity than all other ions. In both panels, the upper sequence is read from the b-ions, and the lower sequence is read from the y-ions. Further note that also the a5- to a8-ions can be distinguished in the upper panel, and the a5- and a6-ions in the lower panel. See text for more explanation.