Hi,
Using the radius of gyration restraint is similar to using an
experimental term.
First, you need to set up the restraint, and then you have to turn on
its flag.
To set up the restraint, use the COLLapse statement at the top of your
script, near where you read in the NOEs:
collapse
assign (aSelection) 100.0 aTargetValue
scale 1.0
end
To turn it on, include COLL in your flags statement:
flags exclude * include bond angle improper ... noe coll end
You need to keep in mind a few things in order to set up the restraint
properly:
1. The selections should not include any flexible regions.
2. The target value (in Angstroms) should be (2.2 * Nresidues^0.38) - 1
where Nresidues is the number of residues in the selection.
3. For anisotropic structures, you need to divide up your structure
into several roughly spherical pieces and create a separate COLLapse
ASSIgn
statement for each.
Other than those caveats, the Rgyr restraint is relatively
bulletproof--it's
not particularly sensitive to the force constant or whatever. And it
doesn't
affect sampling or convergence.
Share and Enjoy,
JK
On Saturday, February 8, 2003, at 10:02 PM, Mike Mesleh wrote:
> Hi there--
> I am wondering how to incorporate a simple radius of gyration
> restraint into the structure calculation. Can I just turn it on by
> adding a flag?
>
> Mike Mesleh
>
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