On 4/29/12 4:46 AM, J B wrote:
 > Is the problem specific to cylinder geometry? Do other settings work? Does it
 > make a difference if you set values for pull_r0 and pull_r1?
 >
 > -Justin

I would think that it is the cylinder geometry that creates the problem.

If I use

pull = umbrella
pull_geometry = distance
pull_dim = N N Y
pull_start = yes
pull_init1= 0.0
pull_ngroups = 1
pull_group0 = DPPC
pull_group1 = drug
pull_rate1 = 0.0

The molecules stays in place. But pull_geometry=distance is what I would prefer
due to the undulations.

Changing pull_r0 and pull_r1 still makes the drug molecule move down towards the
membrane...


Does the cylinder geometry work if you use "pull_start = no" and pull_init1 equal to your starting (restraint) distance? I'm just trying to go through all of the iterations of what might be failing. In theory, what you're doing is fine but I'd be interested to know if there was something failing in the input parsing such that pull_start is not being properly applied. The screen output of grompp will also tell you what it believes the restraint distance is. If it prints 0, then there's a problem with input processing.

If the problem is reproducible in the latest Gromacs version (4.5.5), please file a bug report on redmine.gromacs.org so that it can be investigated. Please provide .tpr file of the system so that the developers can run what you are trying to do and see.

-Justin

--
========================================

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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