[gmx-users] Question about annealing and thermostat

[Leonardo Sepulveda Durán]

hello!!

I am making high temperature simulations (500 K) and to avoid abrupt
disruption of structure I use

Tcoupl                  = berendsen
tau_t                   = 0.1     0.1
tc-grps                 = Protein SOL
ref_t                   = 498     498

Pcoupl                 = berendsen
tau_p                   = 0.5
compressibility         = 4.5e-5        ; compresibilidad del H2O a
300K y 1 atm (en bar-1);
ref_p                   = 1.0

annealing               = single single
annealing_npoints       = 2      2
annealing_time          = 0 50   0 50
annealing_temp          = 1 500  1 500

the last annealing command make a linear increase of temperature from
1 to 500 K in 50 ps.  I have found that just after reach equilibrium
temperature my protein unfolds, but in a unexpected way. It seems
extrange to me this behaviour, so I though I would be having a problem
with temperature copntrol with berendsen and annealing. With that
.mdp, what does the program exactly? rises temperature and then leaves
the berendsen coupling  at 500? or it uses another method? I am
confused.

Leonardo