[gmx-users] Re: PMF of ligand transport

Justin A. Lemkul jalemkul at vt.edu
Mon May 10 18:13:29 CEST 2010

Justin A. Lemkul wrote:
> Aswathy wrote:
>> Hi Justin,
>> I am sorry, i dint understand this point "Your problem was only 
>> related to the actual umbrella sampling itself." ? You meant I just 
>> want to repeat umbrella sampling only?
> Yes.  The manner in which you generate the initial configurations on 
> which you will conduct umbrella sampling is quite irrelevant.
>> In order to further understand that "Distance " problem, May I ask one 
>> more question,( please ignore if its a stupid one..)
>> As Thomas suggested, = is the channel and x the dummy and l the ligand
>> x l =====
>> later time
>> x   ==l==
>> If this is the case, then  there wont be sign problem with "distance", 
>> right???  (Once again forgive me if I am wrong, because I know you 
>> already put your maximum effort to make me understand this thing)
>>  And if we use a dummy particle, will the movement  of that particle 
>> will also matter ? How can we fix that?
> I think this is a rather complicated approach and you will probably 
> spend a lot of unnecessary time troubleshooting it.  It might work, but 
> you don't need it. Your problem is not with the SMD portion of the 
> protocol.  Your problem is with umbrella sampling, which is a separate 
> concept.

I think I mis-read Thomas' post, but I'll agree with Chris that this approach is 
still rather complicated and potentially error-prone.  Using the appropriate 
pull_geometry and a sensible reference group during umbrella sampling is all you 
need to do.



Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080


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