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    Hi Jason,<br>
    <br>
    Oleg is correct, you can assign the ligand and PHE different
    non-blanc altlocs (say A and B). In this case PHE and ligand will
    not 'see' each other via repulsion term of restraints. Also, their
    occupancies will be refined independently and will be constrained to
    be within 0 and 1, but it will not make sure that they add up to 1.
    If you want them to add up to 1, then make a parameter file with a
    constrained group as described in one of examples here:<br>
    <br>
    "13 typical occupancy refinement scenarios and available options in
    phenix.refine"<br>
    <a class="moz-txt-link-freetext" href="http://phenix-online.org/newsletter/">http://phenix-online.org/newsletter/</a><br>
    <br>
    You can do it in the GUI too.<br>
    <br>
    Let us know if you more questions or problems!<br>
    <br>
    Pavel<br>
    <br>
    <div class="moz-cite-prefix">On 3/2/18 02:57, Oleg Sobolev wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CADd3otGuVs-pmOoSsTeO6kSZM91g5ZVn8YnQkFUCNdW2KNA72w@mail.gmail.com">
      <div dir="ltr">Hi Jason,
        <div><br>
        </div>
        <div class="gmail_extra">
          <div class="gmail_quote">
            <blockquote class="gmail_quote" style="margin:0 0 0
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                <div>The ligand and APHE got pushed away from one
                  another and off of their respective densities.
                  Occupancies for both were reduced to 0.5 for the
                  refinement. What am I doing wrong here? Does the
                  ligand need to have an altloc as well? But I don’t see
                  an alternative conformation. </div>
              </div>
            </blockquote>
            <div><br>
            </div>
            <div>Yes, the ligand also needs an altloc, and it should be
              different from PHE altloc. This way the refinement will
              know that these atoms don't see each other. You don't have
              to put two alternative conformations for the ligand, you
              can have just one with partial occupancy (&lt;1.0) which
              will mean that the ligand is not always there.</div>
            <div> </div>
            <div>Best regards,</div>
            <div>Oleg Sobolev.</div>
            <blockquote class="gmail_quote" style="margin:0px 0px 0px
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                <br>
                <div>
                  <blockquote type="cite">
                    <div>On Feb 28, 2018, at 5:35 PM, van den Bedem,
                      Henry &lt;<a
                        href="mailto:vdbedem@slac.stanford.edu"
                        target="_blank" moz-do-not-send="true">vdbedem@slac.stanford.edu</a>&gt;
                      wrote:</div>
                    <br
                      class="m_8858005827093028639Apple-interchange-newline">
                    <div>
                      <div class="m_8858005827093028639WordSection1"
style="font-family:Helvetica;font-size:14px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
                        <div style="margin:0in 0in
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                          If the phe is a gatekeeper, shouldn’t the
                          ligand be refined at partial occupancy; i.e.
                          occupancies not necessarily have to ‘add up’
                          as you suggest? Maybe this link is helpful
                          too:<span
                            class="m_8858005827093028639Apple-converted-space"> </span><a
href="http://www.biorxiv.org/content/early/2018/01/24/253419"
                            style="color:rgb(149,79,114);text-decoration:underline"
                            target="_blank" moz-do-not-send="true">www.biorxiv.org/content/<wbr>early/2018/01/24/253419</a></div>
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                           </div>
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                          H</div>
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                            <b><span style="font-size:12pt">From:<span
                                  class="m_8858005827093028639Apple-converted-space"> </span></span></b><span
                              style="font-size:12pt">&lt;<a
                                href="mailto:phenixbb-bounces@phenix-online.org"
style="color:rgb(149,79,114);text-decoration:underline" target="_blank"
                                moz-do-not-send="true">phenixbb-bounces@<wbr>phenix-online.org</a>&gt;
                              on behalf of "Phan, Jason" &lt;<a
                                href="mailto:jason.phan@vanderbilt.edu"
style="color:rgb(149,79,114);text-decoration:underline" target="_blank"
                                moz-do-not-send="true">jason.phan@vanderbilt.edu</a>&gt;<br>
                              <b>Date:<span
                                  class="m_8858005827093028639Apple-converted-space"> </span></b>Wednesday,
                              February 28, 2018 at 1:30 PM<br>
                              <b>To:<span
                                  class="m_8858005827093028639Apple-converted-space"> </span></b>"<a
                                href="mailto:phenixbb@phenix-online.org"
style="color:rgb(149,79,114);text-decoration:underline" target="_blank"
                                moz-do-not-send="true">phenixbb@phenix-online.<wbr>org</a>"
                              &lt;<a
                                href="mailto:phenixbb@phenix-online.org"
style="color:rgb(149,79,114);text-decoration:underline" target="_blank"
                                moz-do-not-send="true">phenixbb@phenix-online.org</a>&gt;<br>
                              <b>Subject:<span
                                  class="m_8858005827093028639Apple-converted-space"> </span></b>[phenixbb]
                              Overlapping ligand-protein side chain
                              density</span></div>
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                        <span class="">
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                            <a
                              name="m_8858005827093028639__MailOriginalBody"
                              moz-do-not-send="true">All, <span
                                class="m_8858005827093028639Apple-converted-space"> </span></a></div>
                          <div>
                            <div style="margin:0in 0in
                              0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                              <span> </span></div>
                          </div>
                          <div>
                            <div style="margin:0in 0in
                              0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                              <span>A piece of a ligand and the side
                                chain of a “gate-keeper” Phe occupy the
                                same space with well-defined features
                                observed for both (resolution is 1.7 A).
                                It looks about 50:50. How do you refine
                                both ligand and protein side chain in
                                this case? A couple of phenixbb
                                suggestions for dealing with
                                ligand-ligand overlapping density have
                                been considered. With the first
                                suggestion, the two entities still
                                clashed and moved apart off of their
                                respective densities. The second
                                suggestion is not applicable in this
                                case since the other molecule is not a
                                ligand but part of the protein but it
                                was tested anyway. Although there was no
                                bumping, the occupancies don’t add up,
                                resulting in a big blob of negative
                                density around the ligand piece. </span></div>
                          </div>
                          <div>
                            <div style="margin:0in 0in
                              0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                              <span> </span></div>
                          </div>
                          <div>
                            <div style="margin:0in 0in
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                              <span>------------------------------</span></div>
                          </div>
                          <div>
                            <div>
                              <div style="margin:0in 0in
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                                <span>Only two comments:</span></div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span> </span></div>
                            </div>
                            <ol start="1"
                              style="margin-bottom:0in;margin-top:0in"
                              type="a">
                              <li class="MsoNormal" style="margin:0in
                                0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span>At that resolution, constrained
                                  group occupancy refinement should work
                                  reasonably well (provided you can
                                  model the 2 entities). Then you also
                                  do not have clashes between the
                                  molecules, because Occ(A)+Occ(B)=1,
                                  meaning when one (A) is there, the
                                  other one (B) is not. This works with
                                  refmac (external keyword file); if you
                                  need more sophisticated occupancy
                                  re/constraints SHELXL may offer more
                                  opportunities.</span></li>
                              <li class="MsoNormal" style="margin:0in
                                0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span>There is no necessity for the two
                                  NCS copies of the binding site to look
                                  exactly the same (non-equivalent).
                                  Maybe there is a good reason/story
                                  (accessibility, contacts etc) for one
                                  site to be occupied differently than
                                  the other one. </span></li>
                            </ol>
                            <div>
                              <div style="margin:0in 0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span> </span></div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
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                                <span>Best, BR</span></div>
                            </div>
                          </div>
                          <div>
                            <div style="margin:0in 0in
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                              <span>——————————————</span></div>
                          </div>
                          <div>
                            <div>
                              <div style="margin:0in 0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span><span
                                    style="font-size:10.5pt;font-family:Helvetica">Modeling
                                    two molecules that occupy
                                    overlapping binding sites in a
                                    structure simply involves
                                    designating them as alternate
                                    conformers, with the same chain and
                                    residue number, and an occupancy
                                    that sums to 1.0. For example, if
                                    you have an AMP and an ADP that
                                    occupy the same binding site, you
                                    would define them as</span></span></div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span><span
                                    style="font-size:10.5pt;font-family:Helvetica"> </span></span></div>
                            </div>
                            <div>
                              <div>
                                <div style="margin:0in 0in
                                  0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                  <span><span
                                      style="font-size:10.5pt;font-family:Courier">AAMP
                                      B 501</span></span><span><span
                                      style="font-size:10.5pt;font-family:Helvetica"></span></span></div>
                              </div>
                              <div>
                                <div style="margin:0in 0in
                                  0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                  <span><span
                                      style="font-size:10.5pt;font-family:Courier">BADP
                                      B 501</span></span><span><span
                                      style="font-size:10.5pt;font-family:Helvetica"></span></span></div>
                              </div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span><span
                                    style="font-size:10.5pt;font-family:Helvetica"> </span></span></div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span><span
                                    style="font-size:10.5pt;font-family:Helvetica">and
                                    initially set the occupancies for
                                    the atoms in each conformer to the
                                    ratio (50:50, 30:70, etc.) that you
                                    observe in the density.</span></span></div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span><span
                                    style="font-size:10.5pt;font-family:Helvetica"> </span></span></div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span><span
                                    style="font-size:10.5pt;font-family:Helvetica">Refinement
                                    in this manner is straightforward in
                                    PHENIX.</span></span></div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
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                                <span><span
                                    style="font-size:10.5pt;font-family:Helvetica"> </span></span></div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
                                0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">
                                <span><span
                                    style="font-size:10.5pt;font-family:Helvetica">Diana</span></span></div>
                            </div>
                            <div>
                              <div style="margin:0in 0in
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                                <span><span
                                    style="font-size:10.5pt;font-family:Helvetica">----------------------------</span></span></div>
                            </div>
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                        </span></div>
                    </div>
                  </blockquote>
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                <br>
              </div>
              <br>
              ______________________________<wbr>_________________<br>
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            </blockquote>
          </div>
          <br>
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