The results indicate that unfolding occurs on a fast timescale on the

order of tens of picoseconds once initiated. For comparison, such timescales have been observed AZD0156 datasheet on local/partial unfolding events of larger protein structures [66, 67]. Figure 3 Simulation snapshots and root mean square displacement (or rmsd; see Equation 1) trajectories. Structures for n = 144 during low- and high-temperature simulations. For low temperature (300 K, bottom), the folded three-loop structure remains stable and is an equilibrated state (indicated by the relatively constant RMSD). Increasing the temperature (750 K, top) induces unfolding, after which the unfolded structure equilibrates (larger variation in RMSD due to the oscillations induced by the momentum LY2835219 of unfolding). Adhesion and torsional barriers A recent macroscale investigation has determined that the way these rings behave depends on a single characteristic known as overcurvature [68] or how much more curved the three-loop configuration is than a flat circle of the same circumference. Here, each structure has the same initial overcurvature (equal to three). However, at the molecular scale, where temperature and self-adhesion effects are on the same energetic scale as strain energy, the relationship between curvature and stability is more complex. Indeed, due

to the imposed overcurvature of the three-loop conformation, it could be anticipated that a relaxation of bending strain learn more energy results in the necessary energy to unfold, assuming that Thiamine-diphosphate kinase the energy is sufficient to overcome the energy barrier due to adhesion and/or torsion (a full twist/rotation is necessary to unfold a looped chain). Beyond the RMSD calculation, we track the associated potential energy of the carbyne system at a given temperature as it either remains stable (and in a three-loop configuration) or unfolds. Representative results are plotted in Figure 4. The given example indicates an energy barrier in the order of 200 kcal mol-1 (for n = 126 and an unfolding temperature of 575 K). For all systems (54 to 180 atoms), the energy barriers were approximately 40 kcal mol-1 (n = 54) to 400 kcal mol-1 (n = 180), indicating a

clear length dependence on the unfolding energy. To explore the magnitude of the absolute energy barrier due to torsion and adhesion, small simulations to explicitly quantify the energy of each contribution were undertaken independently (Figure 5). Figure 4 Representative potential energy evolution for various temperatures ( T  = 100, 300, and 575 K) for n  = 126. Initial heating phase (10 ps) increases energy due to temperature until either the structure remains in a folded, stable equilibrium (100, 300 K) or unfolding is triggered (575 K). Unfolding at the critical temperature is characterized by a drop in energy due to the release of bending strain energy and global increase in curvature. Here, the critical unfolding energy barrier is approximately 217 kcal mol-1.