Double difference anomalous maps
I tried the "Isomorphous difference map” action and specified a file for input 1 containing F1+, F1– at one wavelength, and the file input 2 containing F2+,F2– at another wavelength. I selected the appropriate Labels for the columns containing the anomalous data. I then specified in "Advanced Options” to use anomalous differences instead of amplitudes. Will this procedure use the following coefficients for the difference Fourier? ( F1(+) – F1(–) ) – ( F2(+) – F2(–) ), alpha(calc) Can someone confirm if this is indeed what is calculated? Many thanks, Mark Saper __________________ Mark A. Saper, Ph.D. Visiting Professor at the Faculty of Medicine Hebrew University of Jerusalem Ein Kerem Jerusalem ISRAEL [email protected] mobile +972 52 815-0480 Powered by Mailbutler https://www.mailbutler.io/?utm_source=watermark&utm_medium=email&utm_campaign=watermark-variant-primary, the email extension that does it all
Hi Mark,
I tried the "Isomorphous difference map” action and specified a file for input 1 containing F1+, F1– at one wavelength, and the file input 2 containing F2+,F2– at another wavelength. I selected the appropriate Labels for the columns containing the anomalous data. I then specified in "Advanced Options” to *use anomalous differences instead of amplitudes*. Will this procedure use the following coefficients for the difference Fourier?
( F1(+) – F1(–) ) – ( F2(+) – F2(–) ), alpha(calc)
Can someone confirm if this is indeed what is calculated?
no, not quite.. Given two data sets, Fobs1 and Fobs2, and a phase source (eg., atomic model), it computes (Fobs1-scale*Fobs2, Phase) Fourier map. Both data sets are assumed to be collected from isomorphous crystals (same space groups, unit cells can deviate up to a small tolerance). Phenix treats Fobs(+) and Fobs(-) as individual data points, so in the map above they will participate as, for example (Fobs1(+)-scale*Fobs2(+), Phase) (Fobs1(-)-scale*Fobs2(-), Phase) Pavel
participants (2)
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Mark Saper -
Pavel Afonine