Re: [AMBER] pbsa: how to increase the sampling volume (grid dimensions)?

From: Ray Luo, Ph.D. <ray.luo.uci.edu>
Date: Wed, 12 Sep 2012 10:39:02 -0700

Jan-Philip,

If you want absolute control of the grid dimension in the final
fine-grid calculation, you have to set nfocus to 1, i.e. no focusing
should be used. Since fillratio only applies to the dimension of the
first grid, i.e. the coarse grid, when nfocus = 2.

Ray

On Wed, Sep 12, 2012 at 10:32 AM, Jan-Philip Gehrcke
<jgehrcke.googlemail.com> wrote:
> Ray,
>
> Actually I missed your answer below. Excuse me. I will look into how
> nfocus changes the behavior I observed. Do you expect fillratio to have
> no effect with nfocus=2?
>
> Thank you!
>
> Jan-Philip
>
>
>
> On 08/22/2012 04:25 PM, Ray Luo wrote:
>> I think fill ratio is the only thing you need to worry about. Of course you don't want to turn on electrostatic focusing, ie nfocus should be set to 1.
>>
>> Ray Luo, Ph.D.
>>
>> On Aug 20, 2012, at 6:24 AM, Jan-Philip Gehrcke <jgehrcke.googlemail.com> wrote:
>>
>>> Let me try to put my question in simpler words:
>>>
>>> I use pbsa for calculating the electrostatic potential of proteins. How
>>> can I enlarge the sampling volume (the absolute grid dimensions) for
>>> this type of calculation? I tried `fillratio`, but failed.
>>>
>>> Any suggestions would be helpful.
>>>
>>> Thanks,
>>>
>>> Jan-Philip
>>>
>>>
>>>
>>> On 07/24/2012 07:13 PM, Jan-Philip Gehrcke wrote:
>>>> Hello,
>>>>
>>>> I'd like to increase the grid dimensions in a PBSA run while keeping the
>>>> spacing constant (just to see more of the distribution of the potential
>>>> in space). I figured that this should be possible through the
>>>> `fillratio` parameter. I did not find any other relevant parameter while
>>>> browsing the documentation.
>>>>
>>>> Hence, I increased fillratio -- however, I did not observe a change in
>>>> the grid dimensions in the DX output file. For my system, I get 55x69x63
>>>> gridpoints in the DX file independent of the fillratio setting.
>>>>
>>>> So, my question is: how do I increase the grid dimensions in a way that
>>>> a *larger* volume is sampled and that the data of the entire sampled
>>>> volume is actually written to the volumetric data file?
>>>>
>>>> What follows now are some more details. I have played around a bit with
>>>> the fillratio setting and used npbverb=1. What I've seen in the pbsa
>>>> output file was the following:
>>>>
>>>> - "Grid dimension at level 2 55 69 63" did not change in
>>>> dependence of fillratio. The data of this grid seems to end up in the DX
>>>> file.
>>>>
>>>> - "Grid dimension at level 1 11 15 13" changes in dependence
>>>> of fillratio (1.0 in this case).
>>>>
>>>> What are the two grid levels good for? Can you help me out here? The
>>>> code in subroutine `pb_setgrd` is way too unstructured for me to follow
>>>> its logic within a reasonable amount of time.
>>>>
>>>> Thanks,
>>>>
>>>> Jan-Philip
>>>>
>>>
>>>
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Received on Wed Sep 12 2012 - 11:00:05 PDT
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