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<p class="MsoNormal"><o:p>&nbsp;</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>&nbsp;</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>&nbsp;</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>&nbsp;</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>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-family:&quot;Times New Roman&quot;,serif">Joel<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:&quot;Times New Roman&quot;,serif"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:&quot;Times New Roman&quot;,serif;color:black;mso-fareast-language:EN-NZ">_________________________________</span><span style="color:black;mso-fareast-language:EN-NZ"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:&quot;Times New Roman&quot;,serif;color:black;mso-fareast-language:EN-NZ">Joel Tyndall, PhD<br>
<br>
Associate Professor in Medicinal Chemistry<br>
National School of Pharmacy<br>
University of Otago<br>
PO Box&nbsp;56 Dunedin 9054<br>
New Zealand&nbsp;&nbsp; </span><span style="color:black;mso-fareast-language:EN-NZ"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:&quot;Times New Roman&quot;,serif;color:black;mso-fareast-language:EN-NZ">Skype: jtyndall<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:&quot;Times New Roman&quot;,serif;color:black;mso-fareast-language:EN-NZ"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.0pt;font-family:&quot;Times New Roman&quot;,serif;color:black;mso-fareast-language:EN-NZ">Ph: &#43;64 3 479 7293<o:p></o:p></span></p>
<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
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