>I think there is a misconception floating around that processing your >data with "anomalous turned on" will somehow degrade the quality of >"normal" intensity data.
I can think of very few circumstances when I would NOT want anomalous data, yet for many data processing pipelines, it is the default not to give you the I+ and I- separately. Anomalous data are very useful for locating metal ions that you might not even have suspected to exist in your structure. Can I make a plea that all data processing packages/pipelines give you anomalous data by default? Can anyone think of a good reason why they shouldn't? James -- Dr. James W. Murray David Phillips Research Fellow Division of Molecular Biosciences Imperial College, LONDON Tel: +44 (0)20 759 48895 ________________________________________ From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of James Holton [jmhol...@lbl.gov] Sent: Wednesday, June 13, 2012 3:47 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Fun Question - Is multiple isomorphous replacement an obsolete technique? I think there is a misconception floating around that processing your data with "anomalous turned on" will somehow degrade the quality of "normal" intensity data. I'm not exactly sure where this rumor comes from, but I imagine it has something to do with confusion about all the various "anomalous" options different scaling programs have. For example, some programs offer the option to treat all I+ and all I- as completely separate data sets, scaled and merged independently. I think this is called "scale anomalous" in SCALEPACK and "intensities anomalous" in SCALA. Neither of these is the default because such treatment is only helpful if the anomalous signal is absolutely huge (I have only seen this once). So, I imagine people who have never done experimental phasing (there are lots of them!) might read things like "Switching ANOMALOUS ON does affect the statistics and the outlier rejection" in the SCALA manual and decide that they had better turn off all those evil "anomalous" things. Then they tell their students to do the same, etc. -James Holton MAD Scientist On Tue, Jun 12, 2012 at 3:17 AM, Eleanor Dodson <eleanor.dod...@york.ac.uk> wrote: > Why would anyone ignore the anomalous data they had collected? It will always > help the phasing, and decide the hand for you.. > Eleanor > On 6 Jun 2012, at 03:55, Stefan Gajewski wrote: > >> 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? Is there a way to look up the answer >> (e.g. filter settings in the RCSB) I am not aware of? >> >> Thanks, >> S. >> >> (Disclaimer: I am aware that isomorpous data is a valuable source of >> information)
