Dear Charles,

Thank you very much for your reply.
Following your suggestion I used a histogram method to estimate Da and 
rhombicity. I also included RDCs corresponding only to  well-structured 
regions of the protein for now. Structures and energies look a little 
better. One thing I am noticing is that Da value in all calculated 
structures hits the maximum of -50. Why this value has been selected as 
DaMax? Is it unrealistic to have Da larger than that?
Thank you,
Irina.



Hello Irina--

>
> I would greatly appeciate your helpful suggestions. We would like to use 
> RDCs
> (only HN) in addition to NOEs to calculate the structure of symmetric 
> dimer. I
> have already calculated NOE-based structures, and use them to estimate Da 
> and
> R parameters using gridsearch.inp. However, the values I get depend very 
> much
> on the starting values of Da and R. calcTensor.py gives me numbers 
> different
> from those that I get by using gridsearch.inp. None of those numbers give 
> me
> an improved structures, when I input them in anneal.py and energies 
> increase
> significantly (up to 12000-20000 kcal/M). What can be the reason for this
> behavior?

my guess is that your structure is not well-enough defined to be able to
be able to determine Da and rhombicity. You will need tp use an
alternate method- like
JOURNAL OF MAGNETIC RESONANCE 133, 216-221 (1998)
or
JOURNAL OF MAGNETIC RESONANCE 149, 271-275 (2001)

I plan on releasing a script which implements one of these algorithms
sometime in the near future.

best regards--
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