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<p>Hi Mark,<br>
</p>
<blockquote type="cite"
cite="mid:BB56CA56-0157-48F3-931F-7AFA4C77B6A3@umich.edu">
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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 <b class="">use
anomalous differences instead of amplitudes</b>. Will this
procedure use the following coefficients for the difference
Fourier?
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre">        </span>( F1(+)
– F1(–) ) – ( F2(+) – F2(–) ), alpha(calc)</div>
<div class=""><br class="">
</div>
<div class="">Can someone confirm if this is indeed what is
calculated?</div>
</blockquote>
<p>no, not quite.. Given two data sets, Fobs1 and Fobs2, and a phase
source (eg., atomic model), it computes <br>
</p>
<p>(Fobs1-scale*Fobs2, Phase) <br>
</p>
<p>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).</p>
<p>Phenix treats Fobs(+) and Fobs(-) as individual data points, so
in the map above they will participate as, for example<br>
</p>
<p>(Fobs1(+)-scale*Fobs2(+), Phase) <br>
</p>
<p>(Fobs1(-)-scale*Fobs2(-), Phase) </p>
<p>Pavel</p>
<p><br>
</p>
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