Re: [gmx-users] atom H is missing in the first residue in a chain

2009-01-14 Thread Justin A. Lemkul



Zhong Zheng wrote:

Hi all

I am running Gromacs on a three-chain protein. The program complains 
about atom H is missing in residue ALA 1 in the pdb file, You might 
need to add atom H to the hydrogen database of residue ALA in the file 
ff???.hdb (see the manual). It's a warning message. I can use the 
option -missing to ignore it. However I would like to understand this. 
It's always the first residue in the chain. So I am thinking this is 
because they are the n-terminus. Then why no complain about c-terminus? 
How can I fix this?




Use -ignh to allow the relevant .hdb file to add the appropriate hydrogens.  The 
problem is that, without -ignh, pdb2gmx expects all atoms (including H) to be 
present in the .pdb file.  If you are using a crystal structure, this 
requirement will not be satisfied.


Likely pdb2gmx does not complain about the C-terminus because it is 
unprotonated, or otherwise the program exits after finding a missing N-terminal 
hydrogen.


As an aside, using -missing is generally a very bad idea, unless you have a very 
specific (and anticipated!) reason to use it.


-Justin


Thanks a lot.


Zhong Zheng
Ph.D candidate
Physics Dept., City College-CUNY
Marshak Science Building J-419 , 
160 Convent Ave, 
New York, NY 10031 USA
Tel: (212)650-6079 
MCCE wiki: scratchpad.wikia.com/wiki/MCCE 
http://scratchpad.wikia.com/wiki/MCCE







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--


Justin A. Lemkul
Graduate Research Assistant
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] atom H is missing in the first residue in a chain

2009-01-14 Thread Zhong Zheng

hi

Thanks for your reply. I tried -ignh and it doesn't help. I understand  
-missing is bad but I made sure the only missing atoms the program  
complains are the first residue in each three chains.
 I am using a crystal structure. However the warning messages are  
only for the first residue in each chain.


Zhong

On Jan 14, 2009, at 1:59 PM, Justin A. Lemkul wrote:




Zhong Zheng wrote:

Hi all
I am running Gromacs on a three-chain protein. The program  
complains about atom H is missing in residue ALA 1 in the pdb  
file, You might need to add atom H to the hydrogen database of  
residue ALA in the file ff???.hdb (see the manual). It's a warning  
message. I can use the option -missing to ignore it. However I  
would like to understand this. It's always the first residue in the  
chain. So I am thinking this is because they are the n-terminus.  
Then why no complain about c-terminus? How can I fix this?


Use -ignh to allow the relevant .hdb file to add the appropriate  
hydrogens.  The problem is that, without -ignh, pdb2gmx expects all  
atoms (including H) to be present in the .pdb file.  If you are  
using a crystal structure, this requirement will not be satisfied.


Likely pdb2gmx does not complain about the C-terminus because it is  
unprotonated, or otherwise the program exits after finding a missing  
N-terminal hydrogen.


As an aside, using -missing is generally a very bad idea, unless you  
have a very specific (and anticipated!) reason to use it.


-Justin


Thanks a lot.
Zhong Zheng
Ph.D candidate
Physics Dept., City College-CUNY
Marshak Science Building J-419 , 160 Convent Ave, New York, NY  
10031 USA
Tel: (212)650-6079 MCCE wiki: scratchpad.wikia.com/wiki/MCCE http://scratchpad.wikia.com/wiki/MCCE 



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--


Justin A. Lemkul
Graduate Research Assistant
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] atom H is missing in the first residue in a chain

2009-01-14 Thread Justin A. Lemkul

What is your exact pdb2gmx command line?

-Justin

Zhong Zheng wrote:

hi

Thanks for your reply. I tried -ignh and it doesn't help. I understand 
-missing is bad but I made sure the only missing atoms the program 
complains are the first residue in each three chains.
 I am using a crystal structure. However the warning messages are only 
for the first residue in each chain.


Zhong

On Jan 14, 2009, at 1:59 PM, Justin A. Lemkul wrote:




Zhong Zheng wrote:

Hi all
I am running Gromacs on a three-chain protein. The program complains 
about atom H is missing in residue ALA 1 in the pdb file, You might 
need to add atom H to the hydrogen database of residue ALA in the 
file ff???.hdb (see the manual). It's a warning message. I can use 
the option -missing to ignore it. However I would like to understand 
this. It's always the first residue in the chain. So I am thinking 
this is because they are the n-terminus. Then why no complain about 
c-terminus? How can I fix this?


Use -ignh to allow the relevant .hdb file to add the appropriate 
hydrogens.  The problem is that, without -ignh, pdb2gmx expects all 
atoms (including H) to be present in the .pdb file.  If you are using 
a crystal structure, this requirement will not be satisfied.


Likely pdb2gmx does not complain about the C-terminus because it is 
unprotonated, or otherwise the program exits after finding a missing 
N-terminal hydrogen.


As an aside, using -missing is generally a very bad idea, unless you 
have a very specific (and anticipated!) reason to use it.


-Justin


Thanks a lot.
Zhong Zheng
Ph.D candidate
Physics Dept., City College-CUNY
Marshak Science Building J-419 , 160 Convent Ave, New York, NY 10031 USA
Tel: (212)650-6079 MCCE wiki: scratchpad.wikia.com/wiki/MCCE 
http://scratchpad.wikia.com/wiki/MCCE


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--


Justin A. Lemkul
Graduate Research Assistant
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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--


Justin A. Lemkul
Graduate Research Assistant
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] atom H is missing in the first residue in a chain

2009-01-14 Thread Justin A. Lemkul



Zhong Zheng wrote:

I tried this: pdb2gmx -f prot.pdb -ignh, not working
What I am using is : pdb2gmx -f prot.pdb -missing



Does the behavior occur when you process each chain separately?

Which force field are you using?  Which version of Gromacs are you using, and 
how was it compiled?  I experienced the same behavior in version 3.3.1, 
resulting from a broken Ubuntu package.


-Justin



On Jan 14, 2009, at 2:16 PM, Justin A. Lemkul wrote:


What is your exact pdb2gmx command line?

-Justin

Zhong Zheng wrote:

hi
Thanks for your reply. I tried -ignh and it doesn't help. I 
understand -missing is bad but I made sure the only missing atoms the 
program complains are the first residue in each three chains.
I am using a crystal structure. However the warning messages are only 
for the first residue in each chain.

Zhong
On Jan 14, 2009, at 1:59 PM, Justin A. Lemkul wrote:



Zhong Zheng wrote:

Hi all
I am running Gromacs on a three-chain protein. The program 
complains about atom H is missing in residue ALA 1 in the pdb 
file, You might need to add atom H to the hydrogen database of 
residue ALA in the file ff???.hdb (see the manual). It's a warning 
message. I can use the option -missing to ignore it. However I 
would like to understand this. It's always the first residue in the 
chain. So I am thinking this is because they are the n-terminus. 
Then why no complain about c-terminus? How can I fix this?


Use -ignh to allow the relevant .hdb file to add the appropriate 
hydrogens.  The problem is that, without -ignh, pdb2gmx expects all 
atoms (including H) to be present in the .pdb file.  If you are 
using a crystal structure, this requirement will not be satisfied.


Likely pdb2gmx does not complain about the C-terminus because it is 
unprotonated, or otherwise the program exits after finding a missing 
N-terminal hydrogen.


As an aside, using -missing is generally a very bad idea, unless you 
have a very specific (and anticipated!) reason to use it.


-Justin


Thanks a lot.
Zhong Zheng
Ph.D candidate
Physics Dept., City College-CUNY
Marshak Science Building J-419 , 160 Convent Ave, New York, NY 
10031 USA
Tel: (212)650-6079 MCCE wiki: scratchpad.wikia.com/wiki/MCCE 
http://scratchpad.wikia.com/wiki/MCCE
 


___
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--


Justin A. Lemkul
Graduate Research Assistant
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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--


Justin A. Lemkul
Graduate Research Assistant
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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--


Justin A. Lemkul
Graduate Research Assistant
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] atom H is missing in the first residue in a chain

2009-01-14 Thread Justin A. Lemkul


Please keep all correspondence on the list.

Zhong Zheng wrote:

Yes.

Amber. Gromacs Version 4.0.2. It's compiled on my computer, macbook. I 
followed standard procedure,nothing special.




The Amber force fields use their own special nomenclature, so N-terminal alanine 
would actually be called NALA.  You will have to modify your .pdb file to 
correspond with Amber naming conventions before this step will complete properly.


-Justin



On Jan 14, 2009, at 2:28 PM, Justin A. Lemkul wrote:




Zhong Zheng wrote:

I tried this: pdb2gmx -f prot.pdb -ignh, not working
What I am using is : pdb2gmx -f prot.pdb -missing


Does the behavior occur when you process each chain separately?

Which force field are you using?  Which version of Gromacs are you 
using, and how was it compiled?  I experienced the same behavior in 
version 3.3.1, resulting from a broken Ubuntu package.


-Justin


On Jan 14, 2009, at 2:16 PM, Justin A. Lemkul wrote:

What is your exact pdb2gmx command line?

-Justin

Zhong Zheng wrote:

hi
Thanks for your reply. I tried -ignh and it doesn't help. I 
understand -missing is bad but I made sure the only missing atoms 
the program complains are the first residue in each three chains.
I am using a crystal structure. However the warning messages are 
only for the first residue in each chain.

Zhong
On Jan 14, 2009, at 1:59 PM, Justin A. Lemkul wrote:



Zhong Zheng wrote:

Hi all
I am running Gromacs on a three-chain protein. The program 
complains about atom H is missing in residue ALA 1 in the pdb 
file, You might need to add atom H to the hydrogen database of 
residue ALA in the file ff???.hdb (see the manual). It's a 
warning message. I can use the option -missing to ignore it. 
However I would like to understand this. It's always the first 
residue in the chain. So I am thinking this is because they are 
the n-terminus. Then why no complain about c-terminus? How can I 
fix this?


Use -ignh to allow the relevant .hdb file to add the appropriate 
hydrogens.  The problem is that, without -ignh, pdb2gmx expects 
all atoms (including H) to be present in the .pdb file.  If you 
are using a crystal structure, this requirement will not be 
satisfied.


Likely pdb2gmx does not complain about the C-terminus because it 
is unprotonated, or otherwise the program exits after finding a 
missing N-terminal hydrogen.


As an aside, using -missing is generally a very bad idea, unless 
you have a very specific (and anticipated!) reason to use it.


-Justin


Thanks a lot.
Zhong Zheng
Ph.D candidate
Physics Dept., City College-CUNY
Marshak Science Building J-419 , 160 Convent Ave, New York, NY 
10031 USA
Tel: (212)650-6079 MCCE wiki: scratchpad.wikia.com/wiki/MCCE 
http://scratchpad.wikia.com/wiki/MCCE
 


___
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--


Justin A. Lemkul
Graduate Research Assistant
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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--


Justin A. Lemkul
Graduate Research Assistant
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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--


Justin A. Lemkul
Graduate Research Assistant
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] atom H is missing in the first residue in a chain

2009-01-14 Thread Justin A. Lemkul



Zhong Zheng wrote:
You mean rename ALA as NALA in the .pdb for the n-terminus Ala? If so, i 
tried already and still not working.




Yes, you would have to rename all N-terminal ALA as NALA, as well as specify the 
correct Amber residue names for all other amino acids in your structure (i.e., 
C-terminal residues, histidines, etc).  An easy way might be to process your 
.pdb with xLeap (now free as part of AmberTools), and use the output .pdb as 
your input into pdb2gmx.


Have you carefully followed all instructions here:

http://chemistry.csulb.edu/ffamber/#usage

Have you updated your aminoacids.dat appropriately (see above link)?

-Justin



On Jan 14, 2009, at 2:38 PM, Justin A. Lemkul wrote:



Please keep all correspondence on the list.

Zhong Zheng wrote:

Yes.
Amber. Gromacs Version 4.0.2. It's compiled on my computer, macbook. 
I followed standard procedure,nothing special.


The Amber force fields use their own special nomenclature, so 
N-terminal alanine would actually be called NALA.  You will have to 
modify your .pdb file to correspond with Amber naming conventions 
before this step will complete properly.


-Justin


On Jan 14, 2009, at 2:28 PM, Justin A. Lemkul wrote:



Zhong Zheng wrote:

I tried this: pdb2gmx -f prot.pdb -ignh, not working
What I am using is : pdb2gmx -f prot.pdb -missing


Does the behavior occur when you process each chain separately?

Which force field are you using?  Which version of Gromacs are you 
using, and how was it compiled?  I experienced the same behavior in 
version 3.3.1, resulting from a broken Ubuntu package.


-Justin


On Jan 14, 2009, at 2:16 PM, Justin A. Lemkul wrote:

What is your exact pdb2gmx command line?

-Justin

Zhong Zheng wrote:

hi
Thanks for your reply. I tried -ignh and it doesn't help. I 
understand -missing is bad but I made sure the only missing atoms 
the program complains are the first residue in each three chains.
I am using a crystal structure. However the warning messages are 
only for the first residue in each chain.

Zhong
On Jan 14, 2009, at 1:59 PM, Justin A. Lemkul wrote:



Zhong Zheng wrote:

Hi all
I am running Gromacs on a three-chain protein. The program 
complains about atom H is missing in residue ALA 1 in the pdb 
file, You might need to add atom H to the hydrogen database of 
residue ALA in the file ff???.hdb (see the manual). It's a 
warning message. I can use the option -missing to ignore it. 
However I would like to understand this. It's always the first 
residue in the chain. So I am thinking this is because they are 
the n-terminus. Then why no complain about c-terminus? How can 
I fix this?


Use -ignh to allow the relevant .hdb file to add the appropriate 
hydrogens.  The problem is that, without -ignh, pdb2gmx expects 
all atoms (including H) to be present in the .pdb file.  If you 
are using a crystal structure, this requirement will not be 
satisfied.


Likely pdb2gmx does not complain about the C-terminus because it 
is unprotonated, or otherwise the program exits after finding a 
missing N-terminal hydrogen.


As an aside, using -missing is generally a very bad idea, unless 
you have a very specific (and anticipated!) reason to use it.


-Justin


Thanks a lot.
Zhong Zheng
Ph.D candidate
Physics Dept., City College-CUNY
Marshak Science Building J-419 , 160 Convent Ave, New York, NY 
10031 USA
Tel: (212)650-6079 MCCE wiki: scratchpad.wikia.com/wiki/MCCE 
http://scratchpad.wikia.com/wiki/MCCE
 


___
gmx-users mailing listgmx-users@gromacs.org
http://www.gromacs.org/mailman/listinfo/gmx-users
Please search the archive at http://www.gromacs.org/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/mailing_lists/users.php


--


Justin A. Lemkul
Graduate Research Assistant
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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Please search the archive at http://www.gromacs.org/search 
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--


Justin A. Lemkul
Graduate Research Assistant
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] atom H is missing in the first residue in a chain

2009-01-14 Thread Zhong Zheng
You mean rename ALA as NALA in the .pdb for the n-terminus Ala? If so,  
i tried already and still not working.



On Jan 14, 2009, at 2:38 PM, Justin A. Lemkul wrote:



Please keep all correspondence on the list.

Zhong Zheng wrote:

Yes.
Amber. Gromacs Version 4.0.2. It's compiled on my computer,  
macbook. I followed standard procedure,nothing special.


The Amber force fields use their own special nomenclature, so N- 
terminal alanine would actually be called NALA.  You will have to  
modify your .pdb file to correspond with Amber naming conventions  
before this step will complete properly.


-Justin


On Jan 14, 2009, at 2:28 PM, Justin A. Lemkul wrote:



Zhong Zheng wrote:

I tried this: pdb2gmx -f prot.pdb -ignh, not working
What I am using is : pdb2gmx -f prot.pdb -missing


Does the behavior occur when you process each chain separately?

Which force field are you using?  Which version of Gromacs are you  
using, and how was it compiled?  I experienced the same behavior  
in version 3.3.1, resulting from a broken Ubuntu package.


-Justin


On Jan 14, 2009, at 2:16 PM, Justin A. Lemkul wrote:

What is your exact pdb2gmx command line?

-Justin

Zhong Zheng wrote:

hi
Thanks for your reply. I tried -ignh and it doesn't help. I  
understand -missing is bad but I made sure the only missing  
atoms the program complains are the first residue in each three  
chains.
I am using a crystal structure. However the warning messages  
are only for the first residue in each chain.

Zhong
On Jan 14, 2009, at 1:59 PM, Justin A. Lemkul wrote:



Zhong Zheng wrote:

Hi all
I am running Gromacs on a three-chain protein. The program  
complains about atom H is missing in residue ALA 1 in the  
pdb file, You might need to add atom H to the hydrogen  
database of residue ALA in the file ff???.hdb (see the  
manual). It's a warning message. I can use the option - 
missing to ignore it. However I would like to understand  
this. It's always the first residue in the chain. So I am  
thinking this is because they are the n-terminus. Then why no  
complain about c-terminus? How can I fix this?


Use -ignh to allow the relevant .hdb file to add the  
appropriate hydrogens.  The problem is that, without -ignh,  
pdb2gmx expects all atoms (including H) to be present in  
the .pdb file.  If you are using a crystal structure, this  
requirement will not be satisfied.


Likely pdb2gmx does not complain about the C-terminus because  
it is unprotonated, or otherwise the program exits after  
finding a missing N-terminal hydrogen.


As an aside, using -missing is generally a very bad idea,  
unless you have a very specific (and anticipated!) reason to  
use it.


-Justin


Thanks a lot.
Zhong Zheng
Ph.D candidate
Physics Dept., City College-CUNY
Marshak Science Building J-419 , 160 Convent Ave, New York,  
NY 10031 USA
Tel: (212)650-6079 MCCE wiki: scratchpad.wikia.com/wiki/MCCE http://scratchpad.wikia.com/wiki/MCCE 



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Department of Biochemistry
Virginia Tech
Blacksburg, VA
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http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin


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Graduate Research Assistant
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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Virginia Tech
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Re: [gmx-users] atom H is missing in the first residue in a chain

2009-01-14 Thread Zhong Zheng
Thanks Justin. I fixed it this time. I basically renamed the terminal  
residues. The reason it didn't work last time is probably because some  
format problem. Thanks again.




On Jan 14, 2009, at 2:50 PM, Justin A. Lemkul wrote:




Zhong Zheng wrote:
You mean rename ALA as NALA in the .pdb for the n-terminus Ala? If  
so, i tried already and still not working.


Yes, you would have to rename all N-terminal ALA as NALA, as well as  
specify the correct Amber residue names for all other amino acids in  
your structure (i.e., C-terminal residues, histidines, etc).  An  
easy way might be to process your .pdb with xLeap (now free as part  
of AmberTools), and use the output .pdb as your input into pdb2gmx.


Have you carefully followed all instructions here:

http://chemistry.csulb.edu/ffamber/#usage

Have you updated your aminoacids.dat appropriately (see above link)?

-Justin


On Jan 14, 2009, at 2:38 PM, Justin A. Lemkul wrote:


Please keep all correspondence on the list.

Zhong Zheng wrote:

Yes.
Amber. Gromacs Version 4.0.2. It's compiled on my computer,  
macbook. I followed standard procedure,nothing special.


The Amber force fields use their own special nomenclature, so N- 
terminal alanine would actually be called NALA.  You will have to  
modify your .pdb file to correspond with Amber naming conventions  
before this step will complete properly.


-Justin


On Jan 14, 2009, at 2:28 PM, Justin A. Lemkul wrote:



Zhong Zheng wrote:

I tried this: pdb2gmx -f prot.pdb -ignh, not working
What I am using is : pdb2gmx -f prot.pdb -missing


Does the behavior occur when you process each chain separately?

Which force field are you using?  Which version of Gromacs are  
you using, and how was it compiled?  I experienced the same  
behavior in version 3.3.1, resulting from a broken Ubuntu package.


-Justin


On Jan 14, 2009, at 2:16 PM, Justin A. Lemkul wrote:

What is your exact pdb2gmx command line?

-Justin

Zhong Zheng wrote:

hi
Thanks for your reply. I tried -ignh and it doesn't help. I  
understand -missing is bad but I made sure the only missing  
atoms the program complains are the first residue in each  
three chains.
I am using a crystal structure. However the warning messages  
are only for the first residue in each chain.

Zhong
On Jan 14, 2009, at 1:59 PM, Justin A. Lemkul wrote:



Zhong Zheng wrote:

Hi all
I am running Gromacs on a three-chain protein. The program  
complains about atom H is missing in residue ALA 1 in the  
pdb file, You might need to add atom H to the hydrogen  
database of residue ALA in the file ff???.hdb (see the  
manual). It's a warning message. I can use the option - 
missing to ignore it. However I would like to understand  
this. It's always the first residue in the chain. So I am  
thinking this is because they are the n-terminus. Then why  
no complain about c-terminus? How can I fix this?


Use -ignh to allow the relevant .hdb file to add the  
appropriate hydrogens.  The problem is that, without -ignh,  
pdb2gmx expects all atoms (including H) to be present in  
the .pdb file.  If you are using a crystal structure, this  
requirement will not be satisfied.


Likely pdb2gmx does not complain about the C-terminus  
because it is unprotonated, or otherwise the program exits  
after finding a missing N-terminal hydrogen.


As an aside, using -missing is generally a very bad idea,  
unless you have a very specific (and anticipated!) reason to  
use it.


-Justin


Thanks a lot.
Zhong Zheng
Ph.D candidate
Physics Dept., City College-CUNY
Marshak Science Building J-419 , 160 Convent Ave, New York,  
NY 10031 USA
Tel: (212)650-6079 MCCE wiki: scratchpad.wikia.com/wiki/ 
MCCE http://scratchpad.wikia.com/wiki/MCCE


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--


Justin A. Lemkul
Graduate Research Assistant
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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Graduate Research Assistant

Re: [gmx-users] atom H is missing in the first residue in a chain

2009-01-14 Thread Tsjerk Wassenaar
Hi Justin/Zhong Zheng,


 Use -ignh to allow the relevant .hdb file to add the appropriate hydrogens.
  The problem is that, without -ignh, pdb2gmx expects all atoms (including H)
 to be present in the .pdb file.  If you are using a crystal structure, this
 requirement will not be satisfied.


It's actually almost opposite: -ignh ignores all hydrogens present,
thus stripping them from the .pdb file. The relevant ones are then
added back from the .hdb database. When you don't use -ignh pdb2gmx
expects all hydrogens in the .pdb file to correspond to atoms listed
for a residue in the .rtp file. If a hydrogen is not present it will
be rebuilt anyway, otherwise the position given will be used. The use
of -ignh is when you have hydrogen atoms listed that are not in the
force field description, like in an NMR file, processed for a united
atom force field. Crystal structures will usually process well without
-ignh, since no hydrogens are present to ignore in the first place :)

Cheers,

Tsjerk

-- 
Tsjerk A. Wassenaar, Ph.D.
Junior UD (post-doc)
Biomolecular NMR, Bijvoet Center
Utrecht University
Padualaan 8
3584 CH Utrecht
The Netherlands
P: +31-30-2539931
F: +31-30-2537623
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