Placing positional restraints with a force constant of 1 kcal mol -1 Å -2 on the backbone atoms, first, the system was heated to 100 K in 50 ps of NVT MD and further heated to 300 K in 5 ps of NPT MD. Further 65 ps of NPT MD were performed for density equilibration, still applying the backbone restraints. Afterward, over the course of further 300 ps of NPT MD, the backbone restraints were gradually reduced to a force constant of 0.2 kcal mol -1 Å -2 .