Many thanks to all who responded to my earlier query (Drs. Paul Swepston, Randy
Read and Nicholas Glykos). I am trying to determine the structure of a very
long coiled
coil dimer (roughly 150 residues long) by molecular replacement. I don't know
if it forms a canonical coiled coil from end to end (it probably doesn't). I
seem to get the right solution using
different lengths of polyala (and polygly and modeled ones with side-chains)
coiled coils as my search models (maps show some density for unmodeled parts of
the coiled coil structure). However, building a model accounting for the entire
sequence, getting the correct chain direction and placing residue side-chains
have proved difficult. And my R-facs have never improved beyond the low 50s
during different refinement attempts. At
the moment, I have 3 more or less contiguous 30 residue stretches of coiled
coil found by 3 independent molecular replacement attempts using epmr (This was
done to account for possible bends, stutters in the dimer). I am trying to get
the rest of the model by new rounds of molecular replacement using epmr. I have
carried out exhaustive runs using epmr. But I haven't found the rest of the
model. What are the options available to me
with molecular replacement? I have tried molrep, phaser and amore from the ccp4
suite. My diffraction data is quite good (data between 25 and 2 A with an Rsym
of 8%). I am currently using Qs on Dr. Glykos' advice. Can I run Qs when a
partial structure is available?
Xie
--- On Sat, 1/24/09, Randy J. Read <rj...@cam.ac.uk> wrote:
From: Randy J. Read <rj...@cam.ac.uk>
Subject: Re: [ccp4bb] brute force molecular replacement
To: CCP4BB@JISCMAIL.AC.UK
Date: Saturday, January 24, 2009, 8:37 PM
Hi,
If you were desperate for BRUTE, I could probably dig out the source code. My
somewhat newer program BEAST also does a brute-force search, and you could get
that by downloading an older version of CCP4 or, again, directly from me.
Our new program Phaser also has brute-force rotation and translation search
options, in addition to the faster FFT-based searches. If you wanted to do a
full 6D brute-force search for a molecule, you'd have to use some tricks,
but it would be possible.
However, the reason we suggested to CCP4 that they should deprecate BEAST is
that we haven't found a case where doing a brute-force search solves a
structure that can't be solved faster with Phaser using the fast search
methods. (If anyone has such a case, we'd be delighted to learn what it has
to teach us!)
Is there a particular reason you'd like to try a brute-force search?
Regards,
Randy Read
On Jan 24 2009, Xie Jiabao wrote:
> Dear all,
>
> From where can I download the molecular replacement program BRUTE? What
are the other brute force programs for molecular replacement out there?
>
> Thanks in advance,
>
> Xie
>
>
>
>
