Atomistic details of the unfolding mechanism of AH1 in the SDM (AP in for v = 0.1 m/s). (A) Atomistic representation of the rupture dynamics. The time interval between these snapshots is 20 ps (between I and II) and 40 ps (between II and III). After 20 ps (I to II), all three HBs have ruptured simultaneously, leading to local unfolding of the protein in the next 40 ps (II to III). These snapshots strongly support the concept of cooperative bond rupture in the SDM. Surrounding water molecules are not shown for reasons of clarity. (B) Rupture sequence of the first four HBs as a function of the applied strain [residue number represents the amino acid of the O atom (H acceptor)]. In the FDM, HBs rupture one by one, whereas in the SDM, several HBs rupture almost simultaneously, within 20 ps. In the FDM, the unfolding wave runs from the pulled residue in the direction of the fixed residue, whereas in the SDM, the unfolding “wave” runs in the opposite direction, nucleating at a random residue within the protein sequence.