Figure 2. αLP unfolds significantly and reproducibly at high temperature but is stable at 298K.
(a) At 500K, αLP unfolds quickly and fully in the five 8.1 ns unfolding simulations while it remains native-like at 298K as measured by Cα RMSD (black, 298K; red, 500K1; green, 500K2; blue, 500K3; orange, 500K4; purple, 500K5). (b,c,d) Colors used are the same as in (a). 500K1 and 500K3 were chosen due to the relatively large difference in their unfolding times. (b) Cα RMSD for the first 4 ns of 298K, 500K1, and 500K3 indicates unfolding occurs early at high temperature. (c) The NPSASA for the first 4 ns of 500K1, 500K3, and 298K is shown. After a short thermal equilibration, both 500K1 and 500K3 reach values ∼5000 Å2 and level off until exposing much more non-polar surface at 1.3 and 1.8 ns, respectively. At 298K, very little increase is seen in NPSASA. (d) ALF measures short-term fluctuations in structure and is an indicator of conformational flexibility of the molecule's current state. For both 500K1 and 500K3, conformational flexibility is low and then suddenly rises concurrently with NPSASA. ALF is low and stable at 298K. For all but (d), the data is smoothed with a 0.019 ns running average.