Anomalous signal even with room temperature capillary data was measurable on diffractometers and early area detectors. However there were misspellings in software packages such as sending anomalous phase 90deg into the wrong direction in one of them or others. After in-house editing, anomalous signal contributed significantly. It was also very instrumental in discovering mis-setings in formats of area detectors. We have used a method as appeared in Tom Blundell and Louise Johnson unrivaled book Protein Crystallography ( I own one!) by checking the peaks of the second derivatives with the phases of the first derivative with the contribution of correct or inverted anomalous signal contribution to get correct detector format or space group or else. I still have a logbook that keep records of getting out correct Xentronics format. So no fiction, just errors… Physics works!!! FF
Dr Felix Frolow Professor of Structural Biology and Biotechnology Department of Molecular Microbiology and Biotechnology Tel Aviv University 69978, Israel Acta Crystallographica F, co-editor e-mail: [email protected] Tel: ++972-3640-8723 Fax: ++972-3640-9407 Cellular: 0547 459 608 On Jun 6, 2012, at 18:02 , Dyda wrote: >> I suspect that pure MIR (without anomalous) was always a fiction. I doubt >> that anyone has ever used it. Heavy atoms always give >> an anomalous signal > >> Phil > > I suspect that there was a time when the anomalous signal in data sets was > fictional. > Before the invent of flash freezing, systematic errors due to decay and the > need > of scaling together many derivative data sets collected on multiple crystals > could render > weak anomalous signal useless. Therefore MIR was needed. Also, current > hardware/software > produces much better reduced data, so weak signals can become useful. > > Fred > > [32m******************************************************************************* > Fred Dyda, Ph.D. Phone:301-402-4496 > Laboratory of Molecular Biology Fax: 301-496-0201 > DHHS/NIH/NIDDK e-mail:[email protected] > Bldg. 5. Room 303 > Bethesda, MD 20892-0560 URGENT message e-mail: [email protected] > Google maps coords: 39.000597, -77.102102 > http://www2.niddk.nih.gov/NIDDKLabs/IntramuralFaculty/DydaFred > *******************************************************************************[m
