[gmx-users] abnormal flip-flop when embedding cholesterol into DOPC using CG

[Jian Dai]

Hi, all:
I'm trying to embed cholesterol molecules into a DOPC bilayer in a coarse
grained model.
The force field and coordinates for a pure DOPC bilayer and for cholesterol
were obtained on the MARTINI's site. I randomly replace a DOPC molecule with
a cholesterol molecule and do the energy minimization. After embedded a
certain amount of cholesterols, I run the simulation by coupling DOPC and
CHOL together to a thermostat. However, the cholesterols turn to be very
unstable and flip-flop a lot between the monolayers, which I think is not
expected.
Any suggestions will be greatly appreciated.Thank you.
dj
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