[gmx-users] RMSF calculations

2011-10-10 Thread Gurunath Katagi
Dear all,
I have a set of proteins(in pdb format) in which some are solved by X-ray
diffraction and some by NMR.
I have done the md simulation of these proteins using gromacs for 30ns [For
NMR structures, i have taken the first model as the starting structure]

Now, that i want to calculate the RMSF value from the simulations and
compare with the RMSF values from experimental structures [X-ray/NMR]
For the proteins with crystal structures , calculation is done using using
g_rmsf function and the comparison is done.

and  for protein from NMR structure , the RMSF values are calculated from
the simulation trajectory. But in order to compare these, how does one get
the RMSF values ? ,since
 the pdb file doesn't have the b-factors ..

Is it a good idea to use the  NMR ensembles ( usually 20 models from NMR) to
derive the RMSF  and compare these with simulation results ..?
or is there any other parameter that i can calculate from NMR models, which
is similar to RMSF ..?

Thanksin advance ..

Thanking You
Gurunath
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Re: [gmx-users] RMSF calculations

2011-10-10 Thread Tsjerk Wassenaar
Hi Gurunath,

Each structure in the NMR ensemble is a fit to the experimental data.
Unlike an MD trajectory, you can not assume that the set of structures
is a proper sample from the Boltzmann distribution, and therefore, the
RMSF can not be expected to correspond to the RMSF of the system. Now,
on a more qualitative level, it is likely that the parts that are less
defined in the NMR ensemble will also have larger RMSFs than the rest,
and could do for a rough comparison.

Hope it helps,

Tsjerk

On Mon, Oct 10, 2011 at 12:22 PM, Gurunath Katagi gurukat...@gmail.com wrote:
 Dear all,
 I have a set of proteins(in pdb format) in which some are solved by X-ray
 diffraction and some by NMR.
 I have done the md simulation of these proteins using gromacs for 30ns [For
 NMR structures, i have taken the first model as the starting structure]

 Now, that i want to calculate the RMSF value from the simulations and
 compare with the RMSF values from experimental structures [X-ray/NMR]
 For the proteins with crystal structures , calculation is done using using
 g_rmsf function and the comparison is done.

 and  for protein from NMR structure , the RMSF values are calculated from
 the simulation trajectory. But in order to compare these, how does one get
 the RMSF values ? ,since
  the pdb file doesn't have the b-factors ..

 Is it a good idea to use the  NMR ensembles ( usually 20 models from NMR) to
 derive the RMSF  and compare these with simulation results ..?
 or is there any other parameter that i can calculate from NMR models, which
 is similar to RMSF ..?

 Thanksin advance ..

 Thanking You
 Gurunath

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-- 
Tsjerk A. Wassenaar, Ph.D.

post-doctoral researcher
Molecular Dynamics Group
* Groningen Institute for Biomolecular Research and Biotechnology
* Zernike Institute for Advanced Materials
University of Groningen
The Netherlands
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