Re: [ccp4bb] Fwd: [ccp4bb] Wyckoff positions and protein atoms

2010-12-16 Thread Jon Wright
On 16/12/2010 12:24, Ian Tickle wrote: I think this is how the Oxford CRYSTALS software ( http://www.xtl.ox.ac.uk/crystals.html ), which has been around for at least 30 years, deals with this issue, so I can't accept that it can't be made to work, even if I haven't got all the precise details

Re: [ccp4bb] Fo-Fo Difference Map

2010-05-05 Thread Jon Wright
Ian Tickle replied: (freezing soaking can easily induce 1% and sometimes 5% change), is surely the reason that Fo-Fo maps never caught on! I've been curious about this unit cell constant mis-matching for a while. If I understood well, Perutz tried to exploit the effect

Re: [ccp4bb] Computer hardware and OS survey

2009-05-01 Thread Jon Wright
Link,Todd M wrote: ... I did not find an equal web support page for Windows. It just isn't needed. If there is a windows version of a program you get to download, install, run and then get on with your life. Jon

Re: [ccp4bb] How small is a microbeam?

2009-04-21 Thread Jon Wright
Sanishvili, Ruslan wrote: .. Reasons for discriminating 5-10 micron beams (minibeam) from ca 1 micron (microbeam) might have been not so much their size but what it involved to achieve these sizes. Might I ask - do you really get data from 1 micron protein crystals? The reduction in

Re: [ccp4bb] Reindexing Orthorhombic

2009-04-17 Thread Jon Wright
James Stroud wrote: ... What is the operation to reindex such that real space is rotated 180 about z? These are in P212121. Isn't that the 21 along z in your orthorhomic space group? Just apply it to your MR solution instead, and add an affine normaliser if needed to superpose the

Re: [ccp4bb] Looking for a free program for calculating powder diffraction pattern

2009-02-16 Thread Jon Wright
Dear Owen, The GSAS package can do that: http://www.ccp14.ac.uk/solution/gsas/ It is important to put some values for the solvent contribution if you want to get a meaningful pattern. Shout if you need a hand. Good luck, Jon wob wrote: Hi, I'm looking for a free program for calculating

Re: [ccp4bb] truncate ignorance

2008-09-08 Thread Jon Wright
Borhani, David wrote: ... but I think pretty much everyone has converged on using it for the past many years. Many small molecule crystallographers seem to refine on intensity and so avoid need this procedure. Towards the end of the recent thread Wilson plot from truncated.mtz it had seemed

Re: [ccp4bb] Optimization of needle crystals?

2008-04-16 Thread Jon Wright
You may be able to check whether the cyrstals are protein or detergent this using powder diffraction. (please excuse the shameless plug): Acta Cryst. (2008). A64, 169-180 Powder crystallography on macromolecules I. Margiolaki and J. P. Wright

Re: [ccp4bb] an over refined structure

2008-02-07 Thread Jon Wright
Dear Ed, I don't see how you decouple symmetry mates in the case of a wrong space group. Symmetry mates should agree with each other typically within R_sym or R_merge percent, eg; about 2-5% . Observed and calculated reflections agree within R_Factor of each other, so about 20-30%. The

Re: [ccp4bb] To bathe or not to bathe.

2007-11-25 Thread Jon Wright
It'd be interesting to determine the validity of the assumption that absorption is simply a function of frame number. ... and direction. See, eg: Acta Cryst. (1995). A51, 33-38[ doi:10.1107/S0108767394005726 ] An empirical correction for absorption anisotropy R. H. Blessing Best, Jon

Re: [ccp4bb] The importance of USING our validation tools

2007-08-31 Thread Jon Wright
Think this bounced last time I tried to mail it in, a simulator exists at: http://fable.sourceforge.net/index.php/Farfield_Simulation Jon Eleanor Dodson wrote: ZO has a good point - it is a pain trying to get decent simulated material - maybe there is an employment opportunity here? Eleanor

Re: [ccp4bb] Is anomalous signal a different wavelength?

2007-05-31 Thread Jon Wright
James, At least for diffraction experiments; the photon scatters off of the *crystal lattice*, not any individual electron, so you can conserve the momentum of the photons and the macroscopic crystal without the crystal recoiling too much. Best, Jon Murray, James W wrote: Dear All,

[ccp4bb] Announcement: Workshop on Powder Diffraction with Proteins

2007-04-02 Thread Jon Wright
Workshop on the Development and Direction of Powder Diffraction on Proteins ESRF, Grenoble, France, 22-23 June 2007 http://www.esrf.fr/events/conferences/PowderDiffraction The investigation of protein structures by high-resolution powder X-ray diffraction has been established as a

Re: [ccp4bb] Advice on img proc software

2007-02-19 Thread Jon Wright
The mathcad image processing module is too expensive for my taste. My university has a campus- wide license for Matlab, so it's *free* for me... I have no idea of what it would cost to purchase. [reminder: never compare educational licensing with giving drugs to schoolchildren.] For

Re: [ccp4bb] crytstallographic software

2007-02-19 Thread Jon Wright
Kevin Cowtan wrote: Acta D has for some reason a rather poor impact rating, and J. Appl. Cryst. a rather better one. There is no outlier rejection in the calculations for journal citation reports (eg: impact factors). Congratulations to: Spek AL, Single-crystal structure validation with