Re: [ccp4bb] Stuck rfree - possible non merohedral twinning ?

Hi Juergen other experts Thanks for the suggestions. I was under the impression that the twin laws/operators are to be used if the twinning is merohedral. In my case, it appears as if the twinning is non-merohedral and more over the data i have is processed as P422 which does not have twin

Re: [ccp4bb] Stuck rfree - possible non merohedral twinning ?

Hi Mahesh You might find this paper useful for some background on types of twinning. It explains the difference between merohedral and non-merohedral twinning. http://journals.iucr.org/d/issues/2003/11/00/ba5036/index.html Alice -- Alice Dawson WNH Lab Division of Biological Chemistry and Drug

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Re: [ccp4bb] Purification of a protein

The polybasic head indicative of your protein to have some possible membrane association? Try a detergent in your buffers might help. Also some of the polybasic head for protein need lipid association to be happy (PI and PCh)? Padayatti On Fri, Aug 23, 2013 at 6:27 PM, Jahan Alikhajeh

Re: [ccp4bb] Stuck rfree - possible non merohedral twinning ?

Dear Mahesh, from the images you showed a few days ago I am not convinced the issue is twinning, just overlaps due to the long c-axis. But of course, I do not have have as much info as you, just those images. Unless you are really convinced you have twinning, if you can see what you want to

[ccp4bb] Resolution, R factors and data quality

Hi All, I have collected diffraction images to 1 Angstrom resolution to the edge of the detector and 0.9A to the corner.I collected two sets, one for low resolution reflections and one for high resolution reflections. I get 100% completeness above 1A and 41% completeness in the 0.9A-0.95A

[ccp4bb] Insertion of a Tag protein in of the molecules of a Dimer protein complex

Dear All, I need to insert a tag protein of ~5 kDa in one of the molecules of a dimer protein (size is ~100kDa). To be more precise - The tag need to get itself attached only on one of the dimer molecules. My expertise are not in Cell biology and therefore any suggestion in this regard

Re: [ccp4bb] Stuck rfree - possible non merohedral twinning ?

Hi Mahesh, First of all, I risk going out on a limb here since I have no demonstrable experience concerning your topic. I was trying to solve a non-merohedral dataset for years, and I failed (like failure as defined in the dictionary). That is hardly a reference, but I got to read a little on

Re: [ccp4bb] Resolution, R factors and data quality

Hi Emily, I get 100% completeness above 1A and 41% completeness in the 0.9A-0.95A shell. However, my Rmerge in the highest shelll is not good, ~80%. The Rfree is 0.17 and Rwork is 0.16 but the maps look very good. If I cut the data to 1 Angstrom the R factors improve but I feel the maps

Re: [ccp4bb] Resolution, R factors and data quality

Thanks Yuriy and Pavel, at this resolution one would expect R/Rfree to be ~ 10-11%/12-13% assuming you applied anisotropic B-factor refinement ( and probably having a low symmetry SG). R merge of 80% may be OK if I/sig for high res shell is 2. Yes, I used anisotropic Bfactors and the space