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It's not possible to make a stock solution of 20% Uranyl Acetate. Even making a 10% UA stock is not possible. At best, the solubility of UA is around 7-8 % in water. It's best to make a 5% stock solution, dissolved in water, for example, and add the quantity
of 5%UA to the acetone. The precipitation of UA is likely due to the acetone as UA is not really soluble in acetone. </div>
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Best,</div>
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<div style="font-family:Tahoma; font-size:13px">Kimberley Gibson</div>
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Research Associate, Charles Sindelar Lab<br>
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Dept. Molecular Biophysics and Biochemistry<br>
Yale University<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> 3dem <3dem-bounces@ncmir.ucsd.edu> on behalf of Christopher Peddie <Christopher.Peddie@crick.ac.uk><br>
<b>Sent:</b> Thursday, December 19, 2019 03:56<br>
<b>To:</b> Qiaohui Yang <qiaohui.yang@ymail.com><br>
<b>Cc:</b> 3dem@ncmir.ucsd.edu <3dem@ncmir.ucsd.edu><br>
<b>Subject:</b> Re: [3dem] Precipitation observed after making freeze substitution cocktail containing 5% water</font>
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<p class="x_MsoNormal"><span style="font-size:9.0pt; font-family:"Trebuchet MS",sans-serif">Hi Qiaohui,</span></p>
<p class="x_MsoNormal"><span style="font-size:9.0pt; font-family:"Trebuchet MS",sans-serif"> </span></p>
<p class="x_MsoNormal"><span style="font-size:9.0pt; font-family:"Trebuchet MS",sans-serif">Mix the osmium, water and acetone and cool to -20oC. Then add the uranyl acetate from a stock e.g. 20%. Cooling the mixture in my experience stops the uranyl acetate
from precipitating out.</span></p>
<p class="x_MsoNormal"><span style="font-size:9.0pt; font-family:"Trebuchet MS",sans-serif"> </span></p>
<p class="x_MsoNormal"><span style="font-size:9.0pt; font-family:"Trebuchet MS",sans-serif">Best,</span></p>
<p class="x_MsoNormal"><span style="font-size:9.0pt; font-family:"Trebuchet MS",sans-serif">Chris</span></p>
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<p class="x_MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt; font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt; font-family:"Calibri",sans-serif"> 3dem [mailto:3dem-bounces@ncmir.ucsd.edu]
<b>On Behalf Of </b>Qiaohui Yang<br>
<b>Sent:</b> 19 December 2019 08:39<br>
<b>To:</b> <br>
<b>Subject:</b> [3dem] Precipitation observed after making freeze substitution cocktail containing 5% water</span></p>
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<p class="x_ydp8b0c7ddbmsonormal"><span style="font-size:10.0pt">Hi everyone!</span></p>
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<p class="x_MsoNormal"><span style="font-size:10.0pt">We recently tried to make freeze substitution cocktail consisting of 1% osmium tetroxide, 0.1% uranyl acetate and 5% water but observed that the mixture turned slightly cloudy within 1-2 minutes. We tried
to see if the precipitation would occur in the absence of osmium tetroxide, and we observed some cloudiness too after mixing uranyl acetate solution in water with pure acetone.</span></p>
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<p class="x_ydp8b0c7ddbmsonormal"><span style="font-size:10.0pt">Just wondering if anyone has encountered similar problem and if so, would appreciate some tips on how to overcome this problem.</span></p>
<p class="x_ydp8b0c7ddbmsonormal"><span style="font-size:10.0pt">Thank you!</span></p>
<p class="x_ydp8b0c7ddbmsonormal"><span style="font-size:10.0pt"> </span></p>
<p class="x_ydp8b0c7ddbmsonormal"><span style="font-size:10.0pt">Best regards,</span></p>
<p class="x_ydp8b0c7ddbmsonormal"><span style="font-size:10.0pt">Qiaohui</span></p>
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