Re: [gmx-users] g_wham problem with negative COM differences

2012-04-18 Thread Anni Kauko
 Anni Kauko wrote:
  
   Date: Wed, 11 Apr 2012 08:38:05 -0400
   From: Justin A. Lemkul jalem...@vt.edu mailto:jalem...@vt.edu
 
   Subject: Re: [gmx-users] g_wham problem with negative COM
 differences
   To: Discussion list for GROMACS users gmx-users@gromacs.org
   mailto:gmx-users@gromacs.org
   Message-ID: 4f857b2d.3050...@vt.edu
 mailto:4f857b2d.3050...@vt.edu
   Content-Type: text/plain; charset=ISO-8859-1; format=flowed
  
  
  
   Anni Kauko wrote:
 Hi!

 I try to perform pmf calculations for case where a peptide
 shifts
 through the membrane. My COM differences should vary from 2.3 to
   -2.5.

 My problem is that g_wham plots negative COM difference as they
   would be
 positive.  In pullx-files the COM differences are treated
 correctly
 (look below). My peptide is not symmetric, so profile curves
 are not
 symmetric, so loosing the sign for COM difference screws my
 profile
 curve completely.

 I did not manage to find any pre-existing answers to this
 problem
   from
 internet.

 First datalines from pullx files:
 (sorry for strange file names...)

 pull_umbr_0.xvg:
 0.  6.26031 2.27369

 pullz_umbr_23.xvg:
 0.  6.09702 0.0233141

 pullz_umbr_50.xvg:
 0.  6.02097 -2.50088

 g_wham command:
 g_wham -b 5000 -it tpr_files.dat  -ix pullz_files.dat -o
 profile_test.xvg -hist histo_test.xvg  -unit kCal

 My pull code:

 pull= umbrella
 pull_geometry   = distance
 pull_dim= N N Y
 pull_start  = yes
 pull_ngroups= 1
 pull_group0 = POPC_POPS ; reference group is bilayer
 pull_group1 = C-alpha__r_92-94 ; group that is actually
 pulled
 pull_init1  = 0
 pull_rate1  = 0.0
 pull_k1 = 1000 ; kJ mol-1 nm-2

  
   Your problem stems from the use of distance geometry.  This
 method
   assumes the
   sign along the reaction coordinate does not change, i.e. always
   positive or
   always negative.  If the sign changes, this simple method fails.
You should be
   using something like position to allow for a vector to be
   specified.  Perhaps
   you can reconstruct the PMF by separately analyzing the positive
   restraint
   distances and negative restraint distances (note here that
   distance really
   refers to a vector quantity, and thus it can have a sign), or
   otherwise create
   new .tpr files using position geometry, though I don't know if
   g_wham will
   accept them or not.
  
   -Justin
  
   --
   
  
   Justin A. Lemkul
   Ph.D. Candidate
   ICTAS Doctoral Scholar
   MILES-IGERT Trainee
   Department of Biochemistry
   Virginia Tech
   Blacksburg, VA
   jalemkul[at]vt.edu http://vt.edu | (540) 231-9080
   tel:%28540%29%20231-9080
   http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
  
   
  
  
   Thank's!
  
   I managed to solve my g_wham problem by doing two things:
  
   1. New tpr-files with proper pull code for g_wham.
   2. I also needed to modify signs of pullf values: If value for pullx
   distance was negative, I reversed the sign of corresponding pullf
 value.
   I did that by my own script.
  
   The new pull code:
  
   ; Pull code
  
   pull= umbrella
   pull_geometry   = direction
   pull_vec1   = 0 0 1
   pull_start  = yes
   pull_ngroups= 1
   pull_group0 = POPC_POPS ; reference group is bilayer
   pull_group1 = C-alpha__r_92-94 ; group that is actually pulled
   pull_init1  = 0
   pull_rate1  = 0.0
   pull_k1 = 1000 ; kJ mol-1 nm-2
  
   I am little bit confuced, why I needed to tweak signes of pullf
 values.
   But like that I got the curve that resembles two half curve made for
   positive and negative pullx distances separately. That curve also
 makes
   sense from biochemical point of view.
  
 Such changes do not seem appropriate to me.  If you change the sign of
 the
 pulling force, you change the implication of what that value means.
 What
 happens if you run your simulations with the new (more appropriate)
 .mdp file?
 Do the forces have the same magnitude, but opposite sign?

 I don't think that the problem is so easy fixed. I had with another
 person about a month ago a lengthy discussion on the list.

 The problem is the following:
 If you use 'distance' as pull_geometry the position of the minimum of
 the umbrella potential is determined by the vector connecting the ref-
 and pulled group, but there is no information about the direction

Re: [gmx-users] g_wham problem with negative COM differences

2012-04-18 Thread Justin A. Lemkul



Anni Kauko wrote:


Anni Kauko wrote:
  
   Date: Wed, 11 Apr 2012 08:38:05 -0400
   From: Justin A. Lemkul jalem...@vt.edu
mailto:jalem...@vt.edu mailto:jalem...@vt.edu
mailto:jalem...@vt.edu
   Subject: Re: [gmx-users] g_wham problem with negative COM
differences
   To: Discussion list for GROMACS users
gmx-users@gromacs.org mailto:gmx-users@gromacs.org
   mailto:gmx-users@gromacs.org mailto:gmx-users@gromacs.org
   Message-ID: 4f857b2d.3050...@vt.edu
mailto:4f857b2d.3050...@vt.edu
mailto:4f857b2d.3050...@vt.edu mailto:4f857b2d.3050...@vt.edu
   Content-Type: text/plain; charset=ISO-8859-1; format=flowed
  
  
  
   Anni Kauko wrote:
 Hi!

 I try to perform pmf calculations for case where a peptide
shifts
 through the membrane. My COM differences should vary
from 2.3 to
   -2.5.

 My problem is that g_wham plots negative COM difference
as they
   would be
 positive.  In pullx-files the COM differences are treated
correctly
 (look below). My peptide is not symmetric, so profile curves
are not
 symmetric, so loosing the sign for COM difference screws my
profile
 curve completely.

 I did not manage to find any pre-existing answers to this
problem
   from
 internet.

 First datalines from pullx files:
 (sorry for strange file names...)

 pull_umbr_0.xvg:
 0.  6.26031 2.27369

 pullz_umbr_23.xvg:
 0.  6.09702 0.0233141

 pullz_umbr_50.xvg:
 0.  6.02097 -2.50088

 g_wham command:
 g_wham -b 5000 -it tpr_files.dat  -ix pullz_files.dat -o
 profile_test.xvg -hist histo_test.xvg  -unit kCal

 My pull code:

 pull= umbrella
 pull_geometry   = distance
 pull_dim= N N Y
 pull_start  = yes
 pull_ngroups= 1
 pull_group0 = POPC_POPS ; reference group is
bilayer
 pull_group1 = C-alpha__r_92-94 ; group that is actually
pulled
 pull_init1  = 0
 pull_rate1  = 0.0
 pull_k1 = 1000 ; kJ mol-1 nm-2

  
   Your problem stems from the use of distance geometry.  This
method
   assumes the
   sign along the reaction coordinate does not change, i.e. always
   positive or
   always negative.  If the sign changes, this simple method
fails.
You should be
   using something like position to allow for a vector to be
   specified.  Perhaps
   you can reconstruct the PMF by separately analyzing the
positive
   restraint
   distances and negative restraint distances (note here that
   distance really
   refers to a vector quantity, and thus it can have a sign), or
   otherwise create
   new .tpr files using position geometry, though I don't
know if
   g_wham will
   accept them or not.
  
   -Justin
  
   --
   
  
   Justin A. Lemkul
   Ph.D. Candidate
   ICTAS Doctoral Scholar
   MILES-IGERT Trainee
   Department of Biochemistry
   Virginia Tech
   Blacksburg, VA
   jalemkul[at]vt.edu http://vt.edu http://vt.edu | (540)
231-9080 tel:%28540%29%20231-9080
   tel:%28540%29%20231-9080
   http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
  
   
  
  
   Thank's!
  
   I managed to solve my g_wham problem by doing two things:
  
   1. New tpr-files with proper pull code for g_wham.
   2. I also needed to modify signs of pullf values: If value for
pullx
   distance was negative, I reversed the sign of corresponding pullf
value.
   I did that by my own script.
  
   The new pull code:
  
   ; Pull code
  
   pull= umbrella
   pull_geometry   = direction
   pull_vec1   = 0 0 1
   pull_start  = yes
   pull_ngroups= 1
   pull_group0 = POPC_POPS ; reference group is bilayer
   pull_group1 = C-alpha__r_92-94 ; group that is actually pulled
   pull_init1  = 0
   pull_rate1  = 0.0
   pull_k1 = 1000 ; kJ mol-1 nm-2
  
   I am little bit confuced, why I needed to tweak signes of pullf
values.
   But like that I got the curve that resembles two half

Re: Re: [gmx-users] g_wham problem with negative COM differences

2012-04-13 Thread Anni Kauko
 Date: Wed, 11 Apr 2012 08:38:05 -0400
 From: Justin A. Lemkul jalem...@vt.edu
 Subject: Re: [gmx-users] g_wham problem with negative COM differences
 To: Discussion list for GROMACS users gmx-users@gromacs.org
 Message-ID: 4f857b2d.3050...@vt.edu
 Content-Type: text/plain; charset=ISO-8859-1; format=flowed



 Anni Kauko wrote:
  Hi!
 
  I try to perform pmf calculations for case where a peptide shifts
  through the membrane. My COM differences should vary from 2.3 to -2.5.
 
  My problem is that g_wham plots negative COM difference as they would be
  positive.  In pullx-files the COM differences are treated correctly
  (look below). My peptide is not symmetric, so profile curves are not
  symmetric, so loosing the sign for COM difference screws my profile
  curve completely.
 
  I did not manage to find any pre-existing answers to this problem from
  internet.
 
  First datalines from pullx files:
  (sorry for strange file names...)
 
  pull_umbr_0.xvg:
  0.  6.26031 2.27369
 
  pullz_umbr_23.xvg:
  0.  6.09702 0.0233141
 
  pullz_umbr_50.xvg:
  0.  6.02097 -2.50088
 
  g_wham command:
  g_wham -b 5000 -it tpr_files.dat  -ix pullz_files.dat -o
  profile_test.xvg -hist histo_test.xvg  -unit kCal
 
  My pull code:
 
  pull= umbrella
  pull_geometry   = distance
  pull_dim= N N Y
  pull_start  = yes
  pull_ngroups= 1
  pull_group0 = POPC_POPS ; reference group is bilayer
  pull_group1 = C-alpha__r_92-94 ; group that is actually pulled
  pull_init1  = 0
  pull_rate1  = 0.0
  pull_k1 = 1000 ; kJ mol^-1 nm^-2
 

 Your problem stems from the use of distance geometry.  This method
 assumes the
 sign along the reaction coordinate does not change, i.e. always positive or
 always negative.  If the sign changes, this simple method fails.  You
 should be
 using something like position to allow for a vector to be specified.
  Perhaps
 you can reconstruct the PMF by separately analyzing the positive restraint
 distances and negative restraint distances (note here that distance
 really
 refers to a vector quantity, and thus it can have a sign), or otherwise
 create
 new .tpr files using position geometry, though I don't know if g_wham
 will
 accept them or not.

 -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

 


Thank's!

I managed to solve my g_wham problem by doing two things:

1. New tpr-files with proper pull code for g_wham.
2. I also needed to modify signs of pullf values: If value for pullx
distance was negative, I reversed the sign of corresponding pullf value. I
did that by my own script.

The new pull code:

; Pull code

pull= umbrella
pull_geometry   = direction
pull_vec1   = 0 0 1
pull_start  = yes
pull_ngroups= 1
pull_group0 = POPC_POPS ; reference group is bilayer
pull_group1 = C-alpha__r_92-94 ; group that is actually pulled
pull_init1  = 0
pull_rate1  = 0.0
pull_k1 = 1000 ; kJ mol^-1 nm^-2

I am little bit confuced, why I needed to tweak signes of pullf values. But
like that I got the curve that resembles two half curve made for positive
and negative pullx distances separately. That curve also makes sense from
biochemical point of view.

-Anni

PS. Thank's for your excellent tutorials. They have been indispensable help
for me to get started with gromacs!

-- 

Anni Kauko, Ph.D.
Post Doctoral Researcher

Structural Bioinformatics Laboratory
Dept. of Biosciences, Biochemistry
Åbo Akademi University
20520 Turku, Finland
phone:  +358 (0)2 215 4006
mobile: +358 (0)50-576 8656


-- 
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http://lists.gromacs.org/mailman/listinfo/gmx-users
Please search the archive at 
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Re: [gmx-users] g_wham problem with negative COM differences

2012-04-13 Thread Justin A. Lemkul



Anni Kauko wrote:


Date: Wed, 11 Apr 2012 08:38:05 -0400
From: Justin A. Lemkul jalem...@vt.edu mailto:jalem...@vt.edu
Subject: Re: [gmx-users] g_wham problem with negative COM differences
To: Discussion list for GROMACS users gmx-users@gromacs.org
mailto:gmx-users@gromacs.org
Message-ID: 4f857b2d.3050...@vt.edu mailto:4f857b2d.3050...@vt.edu
Content-Type: text/plain; charset=ISO-8859-1; format=flowed



Anni Kauko wrote:
  Hi!
 
  I try to perform pmf calculations for case where a peptide shifts
  through the membrane. My COM differences should vary from 2.3 to
-2.5.
 
  My problem is that g_wham plots negative COM difference as they
would be
  positive.  In pullx-files the COM differences are treated correctly
  (look below). My peptide is not symmetric, so profile curves are not
  symmetric, so loosing the sign for COM difference screws my profile
  curve completely.
 
  I did not manage to find any pre-existing answers to this problem
from
  internet.
 
  First datalines from pullx files:
  (sorry for strange file names...)
 
  pull_umbr_0.xvg:
  0.  6.26031 2.27369
 
  pullz_umbr_23.xvg:
  0.  6.09702 0.0233141
 
  pullz_umbr_50.xvg:
  0.  6.02097 -2.50088
 
  g_wham command:
  g_wham -b 5000 -it tpr_files.dat  -ix pullz_files.dat -o
  profile_test.xvg -hist histo_test.xvg  -unit kCal
 
  My pull code:
 
  pull= umbrella
  pull_geometry   = distance
  pull_dim= N N Y
  pull_start  = yes
  pull_ngroups= 1
  pull_group0 = POPC_POPS ; reference group is bilayer
  pull_group1 = C-alpha__r_92-94 ; group that is actually pulled
  pull_init1  = 0
  pull_rate1  = 0.0
  pull_k1 = 1000 ; kJ mol^-1 nm^-2
 

Your problem stems from the use of distance geometry.  This method
assumes the
sign along the reaction coordinate does not change, i.e. always
positive or
always negative.  If the sign changes, this simple method fails.
 You should be
using something like position to allow for a vector to be
specified.  Perhaps
you can reconstruct the PMF by separately analyzing the positive
restraint
distances and negative restraint distances (note here that
distance really
refers to a vector quantity, and thus it can have a sign), or
otherwise create
new .tpr files using position geometry, though I don't know if
g_wham will
accept them or not.

-Justin

--


Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu http://vt.edu | (540) 231-9080
tel:%28540%29%20231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin




Thank's!

I managed to solve my g_wham problem by doing two things:

1. New tpr-files with proper pull code for g_wham.
2. I also needed to modify signs of pullf values: If value for pullx 
distance was negative, I reversed the sign of corresponding pullf value. 
I did that by my own script.


The new pull code:

; Pull code

pull= umbrella
pull_geometry   = direction
pull_vec1   = 0 0 1
pull_start  = yes
pull_ngroups= 1
pull_group0 = POPC_POPS ; reference group is bilayer
pull_group1 = C-alpha__r_92-94 ; group that is actually pulled
pull_init1  = 0
pull_rate1  = 0.0
pull_k1 = 1000 ; kJ mol^-1 nm^-2
   
I am little bit confuced, why I needed to tweak signes of pullf values. 
But like that I got the curve that resembles two half curve made for 
positive and negative pullx distances separately. That curve also makes 
sense from biochemical point of view.




Such changes do not seem appropriate to me.  If you change the sign of the 
pulling force, you change the implication of what that value means.  What 
happens if you run your simulations with the new (more appropriate) .mdp file? 
Do the forces have the same magnitude, but opposite sign?



-Anni

PS. Thank's for your excellent tutorials. They have been indispensable 
help for me to get started with gromacs!


Glad to hear it :)

-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


--
gmx-users mailing listgmx-users@gromacs.org
http://lists.gromacs.org/mailman/listinfo/gmx-users
Please search the archive at 
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Please don't post (un)subscribe requests to the list. Use

[gmx-users] g_wham problem with negative COM differences

2012-04-13 Thread Thomas Schlesier

New try, think last time message didn't reached the list :(

 Original-Nachricht 
Betreff: Re: g_wham problem with negative COM differences
Datum: Fri, 13 Apr 2012 14:55:15 +0200
Von: Thomas Schlesier schl...@uni-mainz.de
An: gmx-users@gromacs.org

Anni Kauko wrote:


 Date: Wed, 11 Apr 2012 08:38:05 -0400
 From: Justin A. Lemkul jalem...@vt.edu mailto:jalem...@vt.edu
 Subject: Re: [gmx-users] g_wham problem with negative COM

differences

 To: Discussion list for GROMACS users gmx-users@gromacs.org
 mailto:gmx-users@gromacs.org
 Message-ID: 4f857b2d.3050...@vt.edu

mailto:4f857b2d.3050...@vt.edu

 Content-Type: text/plain; charset=ISO-8859-1; format=flowed



 Anni Kauko wrote:
   Hi!
  
   I try to perform pmf calculations for case where a peptide

shifts

   through the membrane. My COM differences should vary from 2.3 to
 -2.5.
  
   My problem is that g_wham plots negative COM difference as they
 would be
   positive.  In pullx-files the COM differences are treated

correctly

   (look below). My peptide is not symmetric, so profile curves

are not

   symmetric, so loosing the sign for COM difference screws my

profile

   curve completely.
  
   I did not manage to find any pre-existing answers to this

problem

 from
   internet.
  
   First datalines from pullx files:
   (sorry for strange file names...)
  
   pull_umbr_0.xvg:
   0.  6.26031 2.27369
  
   pullz_umbr_23.xvg:
   0.  6.09702 0.0233141
  
   pullz_umbr_50.xvg:
   0.  6.02097 -2.50088
  
   g_wham command:
   g_wham -b 5000 -it tpr_files.dat  -ix pullz_files.dat -o
   profile_test.xvg -hist histo_test.xvg  -unit kCal
  
   My pull code:
  
   pull= umbrella
   pull_geometry   = distance
   pull_dim= N N Y
   pull_start  = yes
   pull_ngroups= 1
   pull_group0 = POPC_POPS ; reference group is bilayer
   pull_group1 = C-alpha__r_92-94 ; group that is actually

pulled

   pull_init1  = 0
   pull_rate1  = 0.0
   pull_k1 = 1000 ; kJ mol-1 nm-2
  

 Your problem stems from the use of distance geometry.  This

method

 assumes the
 sign along the reaction coordinate does not change, i.e. always
 positive or
 always negative.  If the sign changes, this simple method fails.
  You should be
 using something like position to allow for a vector to be
 specified.  Perhaps
 you can reconstruct the PMF by separately analyzing the positive
 restraint
 distances and negative restraint distances (note here that
 distance really
 refers to a vector quantity, and thus it can have a sign), or
 otherwise create
 new .tpr files using position geometry, though I don't know if
 g_wham will
 accept them or not.

 -Justin

 --
 

 Justin A. Lemkul
 Ph.D. Candidate
 ICTAS Doctoral Scholar
 MILES-IGERT Trainee
 Department of Biochemistry
 Virginia Tech
 Blacksburg, VA
 jalemkul[at]vt.edu http://vt.edu | (540) 231-9080
 tel:%28540%29%20231-9080
 http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

 


 Thank's!

 I managed to solve my g_wham problem by doing two things:

 1. New tpr-files with proper pull code for g_wham.
 2. I also needed to modify signs of pullf values: If value for pullx
 distance was negative, I reversed the sign of corresponding pullf

value.

 I did that by my own script.

 The new pull code:

 ; Pull code

 pull= umbrella
 pull_geometry   = direction
 pull_vec1   = 0 0 1
 pull_start  = yes
 pull_ngroups= 1
 pull_group0 = POPC_POPS ; reference group is bilayer
 pull_group1 = C-alpha__r_92-94 ; group that is actually pulled
 pull_init1  = 0
 pull_rate1  = 0.0
 pull_k1 = 1000 ; kJ mol-1 nm-2

 I am little bit confuced, why I needed to tweak signes of pullf

values.

 But like that I got the curve that resembles two half curve made for
 positive and negative pullx distances separately. That curve also

makes

 sense from biochemical point of view.

Such changes do not seem appropriate to me.  If you change the sign of
the
pulling force, you change the implication of what that value means.
What
happens if you run your simulations with the new (more appropriate)
.mdp file?
Do the forces have the same magnitude, but opposite sign?


I don't think that the problem is so easy fixed. I had with another
person about a month ago a lengthy discussion on the list.

The problem is the following:
If you use 'distance' as pull_geometry the position of the minimum of
the umbrella potential is determined by the vector connecting the ref-
and pulled group, but there is no information about

[gmx-users] g_wham problem with negative COM differences

2012-04-11 Thread Anni Kauko
Hi!

I try to perform pmf calculations for case where a peptide shifts through
the membrane. My COM differences should vary from 2.3 to -2.5.

My problem is that g_wham plots negative COM difference as they would be
positive.  In pullx-files the COM differences are treated correctly (look
below). My peptide is not symmetric, so profile curves are not symmetric,
so loosing the sign for COM difference screws my profile curve completely.

I did not manage to find any pre-existing answers to this problem from
internet.

First datalines from pullx files:
(sorry for strange file names...)

pull_umbr_0.xvg:
0.  6.26031 2.27369

pullz_umbr_23.xvg:
0.  6.09702 0.0233141

pullz_umbr_50.xvg:
0.  6.02097 -2.50088

g_wham command:
g_wham -b 5000 -it tpr_files.dat  -ix pullz_files.dat -o profile_test.xvg
-hist histo_test.xvg  -unit kCal

My pull code:

pull= umbrella
pull_geometry   = distance
pull_dim= N N Y
pull_start  = yes
pull_ngroups= 1
pull_group0 = POPC_POPS ; reference group is bilayer
pull_group1 = C-alpha__r_92-94 ; group that is actually pulled
pull_init1  = 0
pull_rate1  = 0.0
pull_k1 = 1000 ; kJ mol^-1 nm^-2


I would appreciate help very much.

-Anni

-- 

Anni Kauko, Ph.D.
Post Doctoral Researcher

Structural Bioinformatics Laboratory
Dept. of Biosciences, Biochemistry
Åbo Akademi University
20520 Turku, Finland
phone:  +358 (0)2 215 4006
mobile: +358 (0)50-576 8656


-- 
gmx-users mailing listgmx-users@gromacs.org
http://lists.gromacs.org/mailman/listinfo/gmx-users
Please search the archive at 
http://www.gromacs.org/Support/Mailing_Lists/Search before posting!
Please don't post (un)subscribe requests to the list. Use the 
www interface or send it to gmx-users-requ...@gromacs.org.
Can't post? Read http://www.gromacs.org/Support/Mailing_Lists

Re: [gmx-users] g_wham problem with negative COM differences

2012-04-11 Thread Justin A. Lemkul



Anni Kauko wrote:

Hi!

I try to perform pmf calculations for case where a peptide shifts 
through the membrane. My COM differences should vary from 2.3 to -2.5.


My problem is that g_wham plots negative COM difference as they would be 
positive.  In pullx-files the COM differences are treated correctly 
(look below). My peptide is not symmetric, so profile curves are not 
symmetric, so loosing the sign for COM difference screws my profile 
curve completely.


I did not manage to find any pre-existing answers to this problem from 
internet.


First datalines from pullx files:
(sorry for strange file names...)

pull_umbr_0.xvg:
0.  6.26031 2.27369

pullz_umbr_23.xvg:
0.  6.09702 0.0233141

pullz_umbr_50.xvg:
0.  6.02097 -2.50088

g_wham command:
g_wham -b 5000 -it tpr_files.dat  -ix pullz_files.dat -o 
profile_test.xvg -hist histo_test.xvg  -unit kCal


My pull code:

pull= umbrella
pull_geometry   = distance
pull_dim= N N Y
pull_start  = yes
pull_ngroups= 1
pull_group0 = POPC_POPS ; reference group is bilayer
pull_group1 = C-alpha__r_92-94 ; group that is actually pulled
pull_init1  = 0
pull_rate1  = 0.0
pull_k1 = 1000 ; kJ mol^-1 nm^-2



Your problem stems from the use of distance geometry.  This method assumes the 
sign along the reaction coordinate does not change, i.e. always positive or 
always negative.  If the sign changes, this simple method fails.  You should be 
using something like position to allow for a vector to be specified.  Perhaps 
you can reconstruct the PMF by separately analyzing the positive restraint 
distances and negative restraint distances (note here that distance really 
refers to a vector quantity, and thus it can have a sign), or otherwise create 
new .tpr files using position geometry, though I don't know if g_wham will 
accept them or not.


-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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Re: [gmx-users] g_wham problem

2009-08-04 Thread accomp lin

Oh, that would be convenient.
 
Thanks.
 

--- 09年8月3日,周一, Justin A. Lemkul jalem...@vt.edu 写道:


发件人: Justin A. Lemkul jalem...@vt.edu
主题: Re: [gmx-users] g_wham problem
收件人: Discussion list for GROMACS users gmx-users@gromacs.org
日期: 2009年8月3日,周一,上午9:01




accomp lin wrote:
  Dear all
  Gromacs 3.3.3 seems to have a problem with g_wham and there is a fixed 
version from David Bostick of Scripps. So, does anybody has this fixed version 
of g_wham or is there anybody know that where I can find it?
  My email address is  accomp...@student.dlut.edu.cn 
mailto:accomp...@student.dlut.edu.cn 
  

The Gromacs 4.0.x series contains a fixed g_wham that can handle the .pdo 
output of Gromacs 3.3.x.  Using this official version might make it easier to 
get technical support, should you need it.

-Justin

 Thanks a lot
 Jiaqi
 
 
 
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-- 

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
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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[gmx-users] g_wham problem

2009-08-02 Thread accomp lin
 
Dear all
 
Gromacs 3.3.3 seems to have a problem with g_wham and there is a fixed version 
from David Bostick of Scripps. So, does anybody has this fixed version of 
g_wham or is there anybody know that where I can find it?
 
My email address is  accomp...@student.dlut.edu.cn 
 
Thanks a lot

Jiaqi



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Re: [gmx-users] g_wham problem

2009-08-02 Thread Justin A. Lemkul



accomp lin wrote:
 
Dear all
 
Gromacs 3.3.3 seems to have a problem with g_wham and there is a fixed 
version from David Bostick of Scripps. So, does anybody has this fixed 
version of g_wham or is there anybody know that where I can find it?
 
My email address is  accomp...@student.dlut.edu.cn 
mailto:accomp...@student.dlut.edu.cn 
 


The Gromacs 4.0.x series contains a fixed g_wham that can handle the .pdo output 
of Gromacs 3.3.x.  Using this official version might make it easier to get 
technical support, should you need it.


-Justin


Thanks a lot
Jiaqi



好玩贺卡等你发,邮箱贺卡全新上线! 
http://cn.rd.yahoo.com/mail_cn/tagline/card/*http://card.mail.cn.yahoo.com/ 






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--


Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
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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