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Check solvent % - as suggested low solvent content means tight packing means poor signal. Check matthews coefficient ? Do you expect several molecules? As suggested - does the model form an oligamer? ( You need to be careful with these - sometimes you generate thm using both crystal and non-crystallographic symmetry.. Check possible alternate SGs. Try pruning your model - look at it in CCP4MG and see if there are extruded loops.. And good luck! Eleanor PS - by the way - you are cutting your data very savagely.. CC1/2 > 0.5 acceptable. On 9 February 2017 at 08:20, <[log in to unmask]> wrote: > Dear Madhurima, > > > > Small protein structures can be very difficult to solve by MR due to an > unfavorable ratio between inter- and intra-molecular vectors in the > pattersons. I am currently also struggling with some data sets myself. > > > > However, there are things you could (and should) try: > > 1) If your search protein forms an oligomer, e.g. dimer, trimer etc., > generate this oligomer and use this as a search model. Having a bigger > search model will significantly increase your signal to noise ratio. > > 2) Try as many different MR programs as you can lay your hand on. > Sometimes one succeeds, where others fail. I would at least try phaser. > > 3) Do not run the program(s) using the default parameters, but > carefully read the manual and adjust the parameters based on the size and > shape of your search protein. If your protein contains cysteines and/or > methionines, you could look if there is any anomalous signal in your home > source data. Getting higher resolution synchrotron data may not hurt as > well. > > > > Good luck! > > Herman > > > > > > *Von:* CCP4 bulletin board [mailto:[log in to unmask]] *Im Auftrag von > *Madhurima Roy > *Gesendet:* Donnerstag, 9. Februar 2017 05:18 > *An:* [log in to unmask] > *Betreff:* [ccp4bb] Problem with MolRep > > > > Hi all, > > I have a small protein which is of 6 kDa including six histidine tag. The > protein crystallized in the conditions given bellow : > > a) 0.1M Sodium acetate trihydrate pH 4.6, 3M NaCl. > > b) 0.1 M Bis-tris pH 5.5, 2M Ammonium sulphate. > > The crystals are plate shaped in both conditions.We collected diffraction > data at our home source using Rigaku RaxisIV and processed the data using > XDS. > > > In spite of good homology, the protein structure cannot be solved by > MolRep , the contrast is very low approx 1.65. The PDB Blast result is > given below: > > > 38.1(total score), 70%(query coverage) 1e-05 (E-value) and 50%(Identity) . > > The screen shot of the statistics showing R factor and quality of fit in > CORRECT.LP file is enclosed below. > > > > Kindly help. > > Thanks in advance. > > Madhurima > > > > > > > > > > >