[gmx-users] Can't unfold the protein

[Hsin-Lin Chiang]

Hi,

I have question about unfolding.
I use three different ways respectively but all failed.
The three way is, 
1. 600K in 20ns, then the system explode.
2. 400K in 10ns, the protein is very stable and the value is almost the same in radius of gyration.
3. heating up from 300K to 400K in 2ns and the other 2ns for 400K only, then the protein is still stable and the value is almost the same in radius of gyration.
Below is the mdp file of the heating.
What's wrong with my system?

regards,
Hsin-Lin
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title        = ttt
cpp                 =  /lib/cpp
constraints         =  hbonds
;define              =  -DFLEX_SPC
integrator          =  md
emtol               =  100.0
emstep              =  0.005
dt                  =  0.002    ; ps !
nsteps              =  2000000  ; total 4 ns
nstcomm             =  500
nstxout             =  500
nstvout             =  500
nstfout             =  500
nstlog              =  500
nstenergy           =  500
nstlist             =  5
ns_type             =  grid
rlist               =  1.
rcoulomb            =  1.
rvdw                =  1.
coulombtype         =  PME
fourierspacing      =  0.12
pme_order           =  4
optimize_fft        =  yes
Tcoupl              =  v-rescale
tc-grps             =  Protein Non-Protein
;tau_t               =  0.1  0.1
tau_t               =  0.2 0.2
ref_t               =  300 300
energygrps          =  A-chain B-chain SOL  NA+
Pcoupl              =  berendsen
Pcoupltype          =  isotropic
;tau_p               =  0.1
tau_p               =  0.25
compressibility     =  5.4e-5
ref_p               =  1.0
gen_vel             =  yes
gen_temp            =  300
gen_seed            =  173529
; Annealing
annealing           =  single single
annealing_npoints   =  21 21
annealing_time      =  0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
annealing_temp      =  300 305 310 315 320 325 330 335 340 345 350 355 360 365 370 375 380 385 390 395 400 300 305 310 315 320 325 330 335 340 345 350 355 360 365 370 375 380 385 390 395 400
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