[ccp4bb] off topic

2009-06-18 Thread Kn Ly
Hello everyone, I am trying to purify a 13 KDa membrane protein using Ni NTA. The protein is solubilised in Triton X 100, 20 mM phosphate buffer, 150 mM NaCl and binds very well to the column. However, it also turns the column brownish. The protein contains 4 cysteine residues so I suspect that th

Re: [ccp4bb] Phantom Crystals

2009-06-18 Thread V. Nagarajan
Is there some sort of consensus on what properties make a crystal diffract well or poorly? For example, solvent content is assumed to be critical. What else? Can crystals even grow if there is short-range (less than beam radius) disorder? Thanks, V. Nagarajan JAN Scientific, Inc. http://janscient

Re: [ccp4bb] Difference Map images

2009-06-18 Thread Tim Gruene
Hello Doug, I understand your arguing, although I do not understand why Fo contains a contribution from the model(led structure). My idea was only supposed to be a backup in case the apo-form had not been measuredcor could not be used. I agree the Fo(complex)-Fo(apo) gives a much more realisti

Re: [ccp4bb] Phantom Crystals

2009-06-18 Thread James Holton
"Phantom Crystals" can easily be achieved by failing to cryoprotect most any crystal, or by a few other common crystal handling methods, but I don't think this is what you were asking about. I do have users bring in what I call "plastic crystals" from time to time, but these crystals that don'

Re: [ccp4bb] Difference Map images

2009-06-18 Thread Doug Ohlendorf
Tim, Not really. Fo's can be viewed as having 3 parts. 1) F from our modeled structure, 2) F from what we can't model. This can be bulk solvent, partial or multiple occupancies in low resolution structures, thermal anisotropy , etc. 3) F from random errors in measuring data. The first F is what we

Re: [ccp4bb] Phantom Crystals

2009-06-18 Thread Martin.Caffrey
A few more examples of what Daniel refers to can be seen in Figure 11 - Nature Protocols 4:706-731, 2009. We encounter them from time to time using the in meso (lipidic cubic phase) method. With experience you get to recognize them for what they are. Martin -Original Message- From: C

[ccp4bb] PhD Position in Structural Biology, Wuerzburg, Germany

2009-06-18 Thread Clemens Grimm
A PhD position in structural biology is available in the group of Prof. Utz Fischer at the Institute of Biochemistry, Biocentre of the Julius Maximilans-University, Wuerzburg/Germany. The successful applicant will work on the crystallographic structure determination of the Survival Motor Ne

Re: [ccp4bb] Phantom Crystals

2009-06-18 Thread Clemens Grimm
Zitat von George DeTitta : I'd appreciate it if people could tell me their experiences with what I would call "phantom crystals", or "ghost crystals". These are objects that display the seeming morphology of crystals (clear facets, sharp edges) ... There is also a second type of "ghost crysta

Re: [ccp4bb] [COOT] Novel maps...

2009-06-18 Thread Ian Tickle
The SIGMAA program has since it was written in the 80's (mainly by Randy of course, but also in part by Eleanor I believe?) used only 1 phase column (= PHIC) for the case where the phases of FWT & DELFWT are equal to PHIC: obviously if they are unequal (e.g. as a result of phase combination) then a

Re: [ccp4bb] [COOT] Novel maps...

2009-06-18 Thread Eleanor Dodson
Well, it makes for consistency between the output when there is not, and is, exptl phase information - in the 2nd case the PHWT is a weighted derivative of the two phase estimates. You could get away with just one of PHWT and PHDELWT since they can only differ bu 180, but that would require wr

Re: [ccp4bb] [COOT] Novel maps...

2009-06-18 Thread Dirk Kostrewa
Dear Eleaonor and CCP4ers, I always wondered, why there are phase columns PHWT, PHDELWT (Refmac) or PH2FOFCWT, PHFOFCWT (phenix.refine) in addition to the PHIC column of the atomic model. In absence of other phase information, the phase should come from the atomic model, only. Best regard

Re: [ccp4bb] Phantom Crystals

2009-06-18 Thread Daniel Picot
The object that approaches the most a ghost to my mind is a picture of a bubble trapped into a lipidic cubic phase of the detergent beta-octyl-glucoside, it can be found in the article from P. Sakya, J.M. Seddon & R. Templer (1994) J.Phys II France 4:1311. I got also crystals of membrane prote