Is the monomer the biggest unit you have to search with? If there is a
dimer, tetramer, etc. that is conserved, you could try searching with that.
On 01/19/14 14:30, Chris Fage wrote:
Thank you all for your responses. I already have a few ideas about how
to approach the problem.
One of my concerns with so monomers per asymmetric unit at lower
resolution was the failure of MR software. Neither PHENIX nor Phaser
MR have made progress. I am fairly new to anomalous methods, having
solved only two structures by SeMet-based SAD. I've certainly picked
up on a number of tricks from the recent messages on heavy atoms, but
I thought my case might be a little unusual. I am confident the space
group is P1, as it was the only viable option when I indexed four
clean albeit low-res datasets.
The monomers are ~38 kDa, and the crystals diffracted to 3.4-3.0 at a
synchrotron.
The conditions for both native and SeMet crystals are:
8-12% PEG 2000 MME, 0.2 M ammonium sulfate, 0.1 M sodium acetate pH 5.5.
Macromolecular seeding of native crystals into SeMet drops yields the
needle-like crystals.
Any further input is greatly appreciated!
Regards,
Chris
On Sat, Jan 18, 2014 at 11:14 AM, Chris Fage <[email protected]
<mailto:[email protected]>> wrote:
Hello Everyone,
I am currently trying to phase a structure with an asymmetric unit
predicted to contain 20-24 monomers (space group P1). The native
crystals, while beautiful in appearance (see attached), only
diffract to ~3.4-3.0 angstroms at best, and SeMet-derived crystals
grow with poor morphology (small needles). Also, based a
fluorescence scan, I know that mercury does not bind appreciably.
Other than screening for a new space group, what options might I
have for phasing this many monomers at lower resolution? Is there
any real chance of solving the structure in this space group?
Thank you in advance for any suggestions!
Regards,
Chris
--
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All Things Serve the Beam
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David J. Schuller
modern man in a post-modern world
MacCHESS, Cornell University
[email protected]
