*** For details on how to be removed from this list visit the *** *** CCP4 home page http://www.ccp4.ac.uk ***
Hello, scenario 2) would be possible if the smaller fragment(s) have the same packing and still provide the same crystal contacts as the original fragment. In that case, the crystals might diffract nicely and you would have to refine the partially missing parts with reduced occupancy. However, given that you can see the fragments on SDS-PAGE, this is nearly as unlikelky as you sofa getting stuck in your staircase the way it did for Dirk Gently. Any case, I would a) get N-terminal sequencing from the bands you see on the gel. b) try to get a mass spec from your crystals in order to know what's in there and whether it is a degradation product or contamination. Tim -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen GPG Key ID = A46BEE1A On Wed, 15 Mar 2006, Debanu Das wrote: > *** For details on how to be removed from this list visit the *** > *** CCP4 home page http://www.ccp4.ac.uk *** > > > Hi, > This is a non-CCP4 question, but I hope to receive some comments and > guidance from the bb members: > > SDS-PAGE analysis on multiple small crystals (~30x30x30 microns) > possibly indicates the presence of 3 species: intact target and two > other bands that could be degraded portion of the target or impurities > from the purification. > > Both native and SeMet data have been collected on these crystals > (3.2-3.4A) which take 15-60 days to appear/grow. They belong to R32 > space group with cell dimensions of ~145x145x515 A. Data can be > processed without any trouble and Rsyms are ~3-5% in lowest shell, > 10-13% overall (for the native). Diffraction spots are good. Most of the > data sets collected do not indicate twinning. > > 1) If there are multiple proteins in the crystal, are they likely to be > in a "complex"? > > OR > > 2) Can the individual species have different compositions in different > regions of the crystal, i.e., they are not really a "complex" but are > present in one asu and not in another (Is that possible,since by > definition, the asu should be the repeating unit and thus have to be of > unique composition)? If that were the case, would such small crystals > still diffract reasonably well? > > If it is most likely to be case (1), I suppose the structure of this > "complex" can be solved in order to get the structure of the actual > target, but it may not be possible to solve if it is case (2). > I would appreciate any comments or pointers to related/similar reports > in the literature or from anecdotal evidence. > > Thanks, > Debanu. >
