<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
mso-margin-top-alt:auto;
margin-right:0cm;
mso-margin-bottom-alt:auto;
margin-left:0cm;
font-size:12.0pt;
font-family:"Times New Roman",serif;}
span.E-MailFormatvorlage18
{mso-style-type:personal;
font-family:"Times New Roman",serif;
color:windowtext;
font-weight:normal;
font-style:normal;}
span.E-MailFormatvorlage19
{mso-style-type:personal;
font-family:"Calibri",sans-serif;
color:#1F497D;}
span.E-MailFormatvorlage20
{mso-style-type:personal-compose;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="DE" link="#0563C1" vlink="#954F72">
<div class="WordSection1">
<p class="MsoNormal"><span style="color:#1F497D;mso-fareast-language:EN-US">Dear Tom,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D;mso-fareast-language:EN-US">Thank you very much for that very interesting paper. Fortunately, we do not observe any convection issues with our Optima as long as the temperature equilibration is at
least 6 h (below that, we see severe issues for many analytes). By the way, there is a very interesting study by Sloutskin et al.:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D;mso-fareast-language:EN-US"><a href="https://www.sciencedirect.com/science/article/pii/S0927775715003180">https://www.sciencedirect.com/science/article/pii/S0927775715003180</a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D;mso-fareast-language:EN-US">They studied convection and layering effects in analytical centrifugation, where similar issues are observed due to the cooling system.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D;mso-fareast-language:EN-US">Best wishes,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D;mso-fareast-language:EN-US">Johannes<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b>Von:</b> RASMB <rasmb-bounces@list.rasmb.org> <b>Im Auftrag von
</b>Laue, Thomas<br>
<b>Gesendet:</b> Dienstag, 9. März 2021 21:41<br>
<b>An:</b> RASMB <rasmb@rasmb.org><br>
<b>Betreff:</b> [RASMB] Boundary convection problem in the Optima ultracentrifuge<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:14.0pt;font-family:"Times New Roman",serif">Dear all-<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:14.0pt;font-family:"Times New Roman",serif">Data acquired using the Optima ultracentrifuge may exhibit boundary convection, thus confounding the precision and accuracy of data analysis and interpretation
from this instrument. Not all instruments exhibit the phenomenon, and the problem is intermittent on others. The root cause are thermal ‘waves’ that travel from the rotor edge towards the center. These waves produce density gradients in the solution which,
in turn, may be driven by the gravitational field to cause turbulent flow and consequent mixing between adjacent sample regions. The problem is most pronounced in low-concentration buffers where little-to-no stabilizing density gradient forms due to solvent
component redistribution.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:14.0pt;font-family:"Times New Roman",serif">There is a paper available describing the problem, its causes, how to detect it and ways to minimize its occurrence:
<a href="https://biorxiv.org/cgi/content/short/2021.03.08.434487v1">https://biorxiv.org/cgi/content/short/2021.03.08.434487v1</a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:14.0pt;font-family:"Times New Roman",serif">Best wishes,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:14.0pt;font-family:"Times New Roman",serif">Tom<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:14.0pt;font-family:"Times New Roman",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:14.0pt;font-family:"Times New Roman",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Professor Emeritus<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">University of New Hampshire<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
</body>
</html>