Chris, > On Jan 19, 2014, at 11:30 AM, Chris Fage <cdf...@gmail.com> 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.
You'll probably get a lot of (good) suggestions on the ccp4bb, but being new to structure solving by anomalous methods, you should seek out someone who can walk with you through low resolution structure solution. As you may have learned, when working at these resolutions, structures just don't 'pop' out. [advertisement] I'd recommend the Rapidata course at BNL, which meets in the spring. When I last spoke with Bob recently, I had the impression there were open positions. You can bring your data and challenge the "experts" (many of whom are directly involved in the crystallography software development). http://www.bnl.gov/RapiData/ Disclaimer: I am not affiliated with the course :) Just an alum. [/advertisement] Cheers, F > 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 <cdf...@gmail.com> 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 >
