Hello Mario, at 1.9A you might even give S-SAD a try, especially if you have access to an inhouse source with the flexibility to collect data with a (real) high multiplicity.
Tim On Thu, Sep 30, 2010 at 02:40:26PM +0200, Mario Milani wrote: > Thank you for the suggestions. The data resolution is 1.9 so i can try > different heavy atoms techniques ... anyway i am really puzzled by the > peculiar assembly in the crystal and on the possible causes... does anyone > know about similar cases? > mario > > > > > Mario, > > beside what you were mentioning, I would definitely try a quick soak > > (10-30 seconds) of the crystals in cryo conditions supplemented with > > halides such as NaBr, or NaI, at pretty high concentrations (say 0.5 M), > > then directly freezing without backsoak. > > If the crystals survive the treatment, with that amount of mols per unit > > cells and surely some good NCS, you should be able to phase pretty easily. > > Well, of course SeMet would be the other option... > > ciao, > > s > > > > On Sep 30, 2010, at 1:54 PM, Mario Milani wrote: > > > >> Dear all, > >> i have a 30 kDa protein that crystallize so far in three different > >> conditions but with the same space group. It initially looks like > >> tetragonal (I4, a=141, b=141, c=208) and then results triclinic (P1, > >> a=141, b=141 c=144, alpha=119, beta=119, gamma=90), hosting about 24 > >> mol. in the unit cell. Other data: self rotation shows the presence of 4 > >> peaks with chi=180; molecular replacement shows the presence of a > >> pseudo-translation peak; DLS made at protein concentration close to > >> crystal growth conditions shows a Rh compatible with something like a > >> tetramer with low polydispersity (about 15%). Do you have any experience > >> with similar asymmetric associations? Do you have any suggestions, > >> beside the addition of ligands to the crystal growth conditions, in > >> order to get a simpler crystallographic assembly? I have some models > >> (with sequence identity less than 25%) in order to try MR but all trials > >> so far did not solve the structure (using balbes, molrep, phaser and > >> epmr). Any suggestion is welcome. > >> Thank you, > >> > >> Mario Milani > > > > > > -- > > Sebastiano Pasqualato, PhD > > IFOM-IEO Campus > > Dipartimento di Oncologia Sperimentale > > Istituto Europeo di Oncologia > > via Adamello, 16 > > 20139 - Milano > > Italy > > > > tel +39 02 9437 5094 > > fax +39 02 9437 5990 > > > > -- -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen phone: +49 (0)551 39 22149 GPG Key ID = A46BEE1A
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