Dear Dror,<br>I first had this problem while working with apomyoglobin and have seen many researchers with the same problem. Nucleic acids contaminate protein purification, contribute to UV absorption and create artifacts in protein concentration determination. It is one of the main causes of misinterpretation of circular dichroism spectra.<br>
Please see the references below for how a possible way to deal with the problem:<br>Hope they help you.<br>Regards,<br>Carlos Ramos<br><br>-<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 12"><meta name="Originator" content="Microsoft Word 12"><link rel="File-List" href="file:///C:%5CUsers%5CCARLOS%7E1%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_filelist.xml"><link rel="themeData" href="file:///C:%5CUsers%5CCARLOS%7E1%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_themedata.thmx"><link rel="colorSchemeMapping" href="file:///C:%5CUsers%5CCARLOS%7E1%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_colorschememapping.xml"><style>
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</style><span style="font-size: 11pt; font-family: "Arial","sans-serif";" lang="PT-BR">Ribeiro-Jr, E.A.,
Ramos, C.H.I. (2004). </span><u><span style="font-size: 11pt; font-family: "Arial","sans-serif";">Origin of the anomalous circular dichroism
spectra of many apomyoglobin mutants.</span></u><span style="font-size: 11pt; font-family: "Arial","sans-serif";"> </span><i style=""><span style="font-size: 11pt; font-family: "Arial","sans-serif";" lang="PT-BR">Anal. Biochem</span></i><span style="font-size: 11pt; font-family: "Arial","sans-serif";" lang="PT-BR">. </span><b style=""><span style="font-size: 11pt; font-family: "Arial","sans-serif"; color: black;" lang="PT-BR">329</span></b><span style="font-size: 11pt; font-family: "Arial","sans-serif"; color: black;" lang="PT-BR">, 300-306. </span><br>
<br>-<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 12"><meta name="Originator" content="Microsoft Word 12"><link rel="File-List" href="file:///C:%5CUsers%5CCARLOS%7E1%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_filelist.xml"><link rel="themeData" href="file:///C:%5CUsers%5CCARLOS%7E1%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_themedata.thmx"><link rel="colorSchemeMapping" href="file:///C:%5CUsers%5CCARLOS%7E1%5CAppData%5CLocal%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_colorschememapping.xml"><style>
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</style><span style="font-size: 11pt; font-family: "Arial","sans-serif";" lang="EN-AU">Correa,
D.H.A., Ramos, C.H.I. (2009) </span><span style="font-size: 11pt; font-family: "Arial","sans-serif";">The use of circular
dichroism spectroscopy to study protein folding, form and function. <i>African
J. Biochem. </i></span><i><span style="font-size: 11pt; font-family: "Arial","sans-serif";" lang="PT-BR">Res.</span></i><span style="font-size: 11pt; font-family: "Arial","sans-serif";" lang="PT-BR"> <span style="">3</span>,
164-173.</span><br><br><div class="gmail_quote">On Mon, May 31, 2010 at 3:51 AM, Dror Noy <span dir="ltr"><<a href="mailto:dror.noy@weizmann.ac.il">dror.noy@weizmann.ac.il</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
Not exactly AUC related but there's a chance to find here a few people who work with proteins and do care about their UV absorption properties:<br>
We make a variety of native and artificial recombinant proteins and often encounter a situation where the apparently pure fraction according to SDS-PAGE gels has its UV absorption peak blue shifted from the expected ~280 nm toward 260 nm. This seems to be a general problem and usually happens when proteins are purified from inclusion bodies. We suspect DNA contamination but so far we were unable to get rid of it. I'd be very grateful for tips from people who experienced this phenomenon and were able to solve it.<br>
Thanks,<br><font color="#888888">
Dror Noy<br>
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</font></blockquote></div><br><br clear="all"><br>-- <br>Carlos Ramos<br>Instituto de Quimica UNICAMP<br>Sala: 19-3521-3144<br>Lab: 19-3521-3036<br>