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    Hi Joel,<br>
    <br>
    as was suggested main.nqh_flips=False should disable this. <br>
    <br>
    However I'm puzzled about this. NQH flips functionality is designed
    to flip these residues such that the clashes are minimized and
    plausible H-bonding is achieved. So I wonder why it is not working
    in your case?<br>
    <br>
    Would it be possible to send me input files (off list) so that I can
    reproduce this and investigate. Also please indicate HIS in
    question.<br>
    <br>
    Thanks,<br>
    Pavel<br>
    <br>
    <div class="moz-cite-prefix">On 7/21/15 02:07, Joel Tyndall wrote:<br>
    </div>
    <blockquote
cite="mid:0DDD35E86921D947AFE9571F16DA7D6B2F707995@ITS-EXM-P05.registry.otago.ac.nz"
      type="cite">
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        <p class="MsoNormal"><o:p> </o:p></p>
        <p class="MsoNormal"><span style="font-family:&quot;Times New
            Roman&quot;,serif">Hi all,<o:p></o:p></span></p>
        <p class="MsoNormal"><span style="font-family:&quot;Times New
            Roman&quot;,serif"><o:p> </o:p></span></p>
        <p class="MsoNormal"><span style="font-family:&quot;Times New
            Roman&quot;,serif">We are trying to optimise a histidine
            interaction where NE2 would ideally make a hydrogen bond
            with an adjacent tyrosine hydroxyl. The starting point
            contains the hydrogen bond. However upon refinement the ring
            flips (chi2 x 180 degrees) to place the CE1 adjacent to the
            tyrosine hydroxyl.
            <o:p></o:p></span></p>
        <p class="MsoNormal"><span style="font-family:&quot;Times New
            Roman&quot;,serif"><o:p> </o:p></span></p>
        <p class="MsoNormal"><span style="font-family:&quot;Times New
            Roman&quot;,serif">Is it possible to stop this as I see no
            reason why phenix.refine would want to do this<o:p></o:p></span></p>
        <p class="MsoNormal"><span style="font-family:&quot;Times New
            Roman&quot;,serif"><o:p> </o:p></span></p>
        <p class="MsoNormal"><span style="font-family:&quot;Times New
            Roman&quot;,serif">Regards<o:p></o:p></span></p>
        <p class="MsoNormal"><span style="font-family:&quot;Times New
            Roman&quot;,serif"><o:p> </o:p></span></p>
        <p class="MsoNormal"><span style="font-family:&quot;Times New
            Roman&quot;,serif">Joel</span><br>
        </p>
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