Re: [ccp4bb] Question about R/Rfree value difference

2010-07-08 Thread Anastassis Perrakis
I do agree with Tim's reasoning in general, but as Pavel also implied by offering the statistics, I would not be worried about the difference, but by the unreasonably high absolute value of Free R for 2.0 A resolution. I do not think that its simple 'over-fitting' and my worry would not be

Re: [ccp4bb] Question about R/Rfree value difference

2010-07-08 Thread Tim Gruene
badly built model reminds me of another possible reason: if you have an old version of ccp4 installed (before 6.1??), there is a default weight of 0.3 for refmac between data and restraints. This value is - in my experience - way too high for normal resolution and at the beginning of refinement

Re: [ccp4bb] Question about R/Rfree value difference

2010-07-08 Thread jbosch
Something else to consider is what is your space group ? P212121 but truly P21 with twinning fraction close to 0.5 ? That's one of my recent cases. 1.9 Å data beautifully refined built but the Rwork/Rfree gap was 13 percent. After changing the space group and applying the twin law the gap is 3

[ccp4bb] idiffdisp - two clicks to define a line does not work on a sector ?

2010-07-08 Thread Boaz Shaanan
Hi,  In idiffdisp (v. 6.1.13 and I presume also in earlier versions), if I read in a bunch of images as a sector, the function 'two clicks to define a line' is not working (it's not lit in fact). This function is quite useful for looking into difficult cases e.g. where weak reflections are

Re: [ccp4bb] Calculate the portion of the density within a mask

2010-07-08 Thread Eleanor Dodson
mapmask will do this. Eleanor See the documentation - it is a bit confalued but certainly works.. Hailiang Zhang wrote: Hi, I want to calculate the portion of the noise density with respect to the whole unit cell (assuming the model is good enough). I plan to first calculate the integral

Re: [ccp4bb] Question about R/Rfree value difference

2010-07-08 Thread Tom Oldfield
Sampath With regard to your question on what sort of statistics you should get within structure determination you might find this service at the PDBe useful : http://www.ebi.ac.uk/pdbe-as/pdbestatistics/PDBeStatistics.jsp You can view and manipulate distributions of R, Rfree and R-Rfree along

[ccp4bb] Postdoctoral Opportunity at Pfizer Cambridge, MA

2010-07-08 Thread Bard, Joel
There is a postdoctoral position in Structural Biology available at the Pfizer site in Cambridge, Massachusetts. The project involves solving the structures of related signalling protein/receptor complexes and then using computational modeling to design new molecules with enhanced specificity.

Re: [ccp4bb] Twin questions: is my crystals twinned or not?

2010-07-08 Thread Anastassis Perrakis
Hi Partha - A few thoughts: 1. If you attach logs, at least gzip them ... 2. From the fact that Rfree goes down when twinning is switched off, I would think there is no twining. 3. The intensity distribution (moment of E, etc) suggest no twining. The twining operator you use is the

Re: [ccp4bb] Twin questions: is my crystals twinned or not?

2010-07-08 Thread Ethan Merritt
On Thursday 08 July 2010 11:03:30 am Parthasarathy Sampathkumar wrote: Dear All, Back ground: This is my first experience with a twined dataset. Crystals belong to a small domain of 132 aa, out of which ~40 residues appears to be disordered (~30 of those from C-terminal and C-term His6

[ccp4bb] Beginning crystallography text

2010-07-08 Thread Peter Hsu
Hi all, I haven't gotten past the phase of growing the crystal, but I'd certainly still like to learn the actual theories of crystallography. Can anyone recommend a good beginner to mid-level text on macromolecular crystallography? Thanks, Peter

Re: [ccp4bb] Beginning crystallography text

2010-07-08 Thread Thomas Juettemann
This book worked great for me: http://www.amazon.com/Crystallography-Made-Crystal-Clear-Third/dp/0125870736/ref=sr_1_3?ie=UTF8s=booksqid=1278618216sr=1-3 Cheers, Thomas On Thu, Jul 8, 2010 at 12:35, Peter Hsu hsuu...@u.washington.edu wrote: Hi all, I haven't gotten past the phase of growing

Re: [ccp4bb] Beginning crystallography text

2010-07-08 Thread Patrick Loll
At the risk of appearing immodest: http://www.amazon.com/Protein-Crystallography-Eaton-E-Lattman/dp/0801888069/ref=sr_1_10?ie=UTF8s=booksqid=1278618335sr=1-10 On 8 Jul 2010, at 3:35 PM, Peter Hsu wrote: Hi all, I haven't gotten past the phase of growing the crystal, but I'd certainly

[ccp4bb] RES: [ccp4bb] Beginning crystallography text

2010-07-08 Thread Júlio César
Hi Peter, I understood your situation and I believe the best literature for you is the Dr. Rupp's Book: Biomolecular Crystallography: Principles, Practice, and Application to Structural Biology Author: Benhard Rupp. Good luck in your studies. Best regards, Júlio César -Mensagem

Re: [ccp4bb] Beginning crystallography text

2010-07-08 Thread Prince, D Bryan
Having recently completed the CSHL Macromolecular crystallography course, I can recommend Introduction to Macromolecular Crystallography by Alexander McPherson (ISBN 987-0-470-18590-2). I am posting the link below:

Re: [ccp4bb] Beginning crystallography text

2010-07-08 Thread Robert Sweet
I like David Blow's book for beginners -- one can get the gist of things without having much math: http://www.abebooks.com/servlet/SearchResults?an=blowsts=ttn=crystallographyx=35y=6 Bernhard Rupp's book, mentioned earlier, is the current gold standard, in my view. Bob On Thu, 8 Jul 2010,

[ccp4bb] Computational Crystallography Newsletter - Issue 1

2010-07-08 Thread Paul Adams
Dear Colleagues, I am pleased to announce the publication of the first issue of the Computational Crystallography Newsletter: http://www.phenix-online.org/newsletter/ It features articles, meeting announcements and reports, information on research and other items of interest

[ccp4bb] How to make fft-map more physically meaningful?

2010-07-08 Thread Hailiang Zhang
Hi there: I found that the grid values in the map file generated by CCP4-fft generally has a mean value of ~0, and of course there will be lots of negative values. This apparently is not the real physics, since the electron density has to be positive everywhere (hope I am right). Can somebody

Re: [ccp4bb] Beginning crystallography text

2010-07-08 Thread Ho Leung Ng
Back when I was a graduate student, my favorite book was Drenth. However, that book was never a favorite with most students, who preferred Crystallography Made Crystal Clear. I also think the Blow book is good. I'm not familiar with the newer books written by our mailing list colleagues. ho

Re: [ccp4bb] How to make fft-map more physically meaningful?

2010-07-08 Thread Edward A. Berry
Hailiang Zhang wrote: Hi there: I found that the grid values in the map file generated by CCP4-fft generally has a mean value of ~0, and of course there will be lots of negative values. This apparently is not the real physics, since the electron density has to be positive everywhere (hope I am

Re: [ccp4bb] How to make fft-map more physically meaningful?

2010-07-08 Thread Dale Tronrud
Edward A. Berry wrote: Hailiang Zhang wrote: Hi there: I found that the grid values in the map file generated by CCP4-fft generally has a mean value of ~0, and of course there will be lots of negative values. This apparently is not the real physics, since the electron density has to be

Re: [ccp4bb] Beginning crystallography text

2010-07-08 Thread Bernhard Rupp
The question of what textbook to use is very much context sensitive, that is, it depends on what the reader wants and needs to know. Unfortunately, this question us easy to answer with hindsight, but not so obvious to the person looking for answers. Having said that, I declare a conflict of