Re: [ccp4bb] SeMet data

2019-08-28 Thread Stefan Gajewski
Hi Lindsey, I do agree with the others on improving your experimental strategy to enhance the anomalous signal in your data, but did you try to solve the structure with the data you already have? I have seen cases where there is only a pathetic anomalous signal from fully Se-Met incorporated

Re: [ccp4bb] align structure in Pymol based on dsDNA helix

2017-05-15 Thread Stefan Gajewski
Dear Xiao Lei, You might want to consider UCSF Chimera for this task https://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/matchalign/matchalign.html Best, Stefan

Re: [ccp4bb] Interesting DNA contamination

2015-06-26 Thread Stefan Gajewski
Pramod, You already got good suggestions on how to handle DNA contamination in protein preparations. Let me point out briefly that you haven't demonstrated yet that your contamination is DNA. I had the same observation when purifying UvsX. A very persistent and strong contamination in all

Re: [ccp4bb] Interesting DNA contamination

2015-06-26 Thread Stefan Gajewski
Correction, I meant to say 0.5kb, not 500kb sorry for that. S.

Re: [ccp4bb] experimental phasing at low resolution

2015-04-28 Thread Stefan Gajewski
Hi, I doubt you have a TaBr cluster bound in your soaks. You'd expect a strong anomalous signal from cluster compounds (that's what they are made for) and you can easily get a low resolution anomalous signal from a few dislocated HA in the solvent channels, especially if you don't counter

[ccp4bb] A crystal symmetry broken beyond repair?

2014-02-22 Thread Stefan Gajewski
I have three brief questions (number two should be the easy one). 1. Where could an extra electron density of an (physically impossible) additional molecule in an otherwise perfect map come from? (even in a wrong solution in a {probably} too high space group?) 2. I would like to see how my data

[ccp4bb] Triclinic solution for a dataset with pseudo-translational symmetry, possible pseudo-centering and possible pseudo-merohedral twinning. How to proceed?

2013-10-18 Thread Stefan Gajewski
back the resolution to preserve the weak reflections on the original scale? feeling a little lost here with all the pseudo symmetries , Stefan Gajewski

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

2013-08-28 Thread Stefan Gajewski
Jim, This is coming from someone who just got enlightened a few weeks ago on resolution cut-offs. I am asked often: What value of CC1/2 should I cut my resolution at? The KD paper mentioned that the CC(1/2) criterion loses its significance at ~9 according to student test. I doubt that this

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

2013-08-26 Thread Stefan Gajewski
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] Where to cut the data in this medium resolution dataset

2013-07-23 Thread Stefan Gajewski
Nat, What do correct B-factors look like? What refinement strategy did you use for them? 1) If I see strong positive density in the Fo-Fc map along the backbone of two turns of an correctly placed alpha helix, therefore the B-factors are too high in that region. The model after refinement

[ccp4bb] Where to cut the data in this medium resolution dataset

2013-07-22 Thread Stefan Gajewski
. Thank you for your input, Stefan Gajewski

[ccp4bb] Fun Question - Is multiple isomorphous replacement an obsolete technique?

2012-06-05 Thread Stefan Gajewski
Hey! I was just wondering, do you know of any recent (~10y) publication that presented a structure solution solely based on MIR? Without the use of any anomalous signal of some sort? When was the last time you saw a structure that was solved without the use of anomalous signal or homology model?

Re: [ccp4bb] Expression of Viral proteins for crystallography

2012-01-24 Thread Stefan Gajewski
Rubén, the previous answer probably addresses your problem accurately. However. If your protein of interest modifies DNA/RNA, it is quite common that your pET constructs will mutate rapidly in E.coli. Lac operons tend to leak quite a bit, which is not enough to detect the protein prior to

Re: [ccp4bb] very strange lattice: high anisotropy, 78% solvent content and maybe merohedral twinning

2011-12-14 Thread Stefan Gajewski
Jürgen, Have you checked a simple selfrotation function in your currently favored space group ? Yes, both selfrotation function and patterson map do not look suspicious in I422. Do you have sufficient data collected to start out in P1 or C2 ? Then I would start there and systematically

[ccp4bb] very strange lattice: high anisotropy, 78% solvent content and maybe merohedral twinning

2011-12-13 Thread Stefan Gajewski
is the recommended protocol when dealing with many and very strongly correlated NCS units, putative twinning and severe anisotropy all at the same time? Stefan Gajewski