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Hi--

Well I'm glad we seem to get the right answer some of the time...

> I have been using a standard annealing script with TAD from CNS 1.0 that
> included sani restraints (only 1 class, HN). Most of the structures had
> no sani violations larger than 1 nor 0.1, as listed in the header of pdb
> file. However, when I loaded the structures in vmd-xplor and displayed
> the dipolar couplings (using the same DFS, Da and R values as for the
> calculations), there were usually several violations larger than 1 or
> even 2. I was quite surprised by this discrepancy. :( I listed all the
> rdc, as calculated by CNS, using the sani print statement (with
> threshhold = 0) and indeed, the values differed quite a bit between CNS
> and vmd-xplor. I thought that this was perhaps some peculiarity of CNS,
> but a sani print statement in xplor-nih (version 2.9.2) gave me
> calculated values of rdcs identical to those from CNS, and different
> from vmd-xplor!!!

the SANI code in Xplor-NIH and CNS is pretty much identical, so it's
not surprising that they give the same answer.

> This does not look quite right, does it? Since I was getting two
> different sets of calculated rdcs, I wrote my own program to calculate
> them from pdb files with ANI residue. My calculated values agree very
> well with vmd-xplor values. This suggests that rdcs calculated by the
> sani statement in xplor are not quite correct - which makes my very
> suspicious about any sani calculations!!! 

Another option for you would be to use the DIPO term in Xplor-NIH- you
might see how that does.

Of course we'd like to fix any bugs in the SANI term. If you could
send me psf, pdb files and a table of SANI assignments which differ I
will look into this. It's best if you could tar these up and ftp them
to dcb.cit.nih.gov/pub/incoming

regards--
Charles

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