<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=us-ascii">
<meta name="Generator" content="Microsoft Word 12 (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;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
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="EN-US" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal">Hi All –<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m doing an equilibrium run on a ~3 KDa synthetic peptide lacking aromatics in 20% TFE. I thought I might use multiple wavelengths to extend the concentration range that I could follow.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I thought I’d be clever and obtain the ratio of extinction coefficients by dividing the absorbance at one wavelength (236 nm) by the other (240 nm) across the cell (rather than using the spectrum).
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I calculated the ratio using only the points that were at the same radial distance and plotted them vs radial distance. It is pretty apparent that the ratio is changing across the cell.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My question is whether this is likely to be an optical artifact or whether it most likely represent heterogeneity in the sample. It is probably worth noting that the ratio from the spectrum is 1.43, intermediate between the extremes seen
across the cell which to me suggests heterogeneity. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Peter<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas">Peter E. Prevelige Jr.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas">Professor<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas">Dept. of Microbiology, BBRB 416/6<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas">Univ. of Alabama @ Birmingham<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas">845 19th St. South<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas">Birmingham AL. 35294-2170<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas">Phone 205 975-5327<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas">FAX 205 975-5479<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas"><a href="mailto:prevelig@uab.edu">prevelig@uab.edu</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Consolas"><a href="http://www.microbio.uab.edu/faculty/prevelige/prevelige-p.htm">http://www.microbio.uab.edu/faculty/prevelige/prevelige-p.htm</a><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</body>
</html>