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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Carlos,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>If your protein is charged then you will definitely need some counter ions in there. That is the most obvious cause for lower than expected sedimentation coefficients. Here is a good paper to start with design, buffer considerations etc etc.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hope this helps, <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Lake<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Analytical Ultracentrifugation in the Study of Protein Selfassociation<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>and Heterogeneous Protein-Protein Interactions <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Andrea Balbo and Peter Schuck</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><p class=MsoNormal><b><i><span style='font-size:10.5pt;font-family:Consolas;color:#1F497D'>Lake N. Paul, PhD<o:p></o:p></span></i></b></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas;color:#1F497D'>Biophysics Research Specialist<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas;color:#1F497D'>Discovery Park - Bindley Biosciences Center Purdue University<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas;color:#1F497D'>1203 West State Street<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas;color:#1F497D'>West Lafayette, Indiana, 47905<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas;color:#1F497D'>765.494.4960<o:p></o:p></span></p><p class=MsoNormal><b><u><span style='font-size:10.5pt;font-family:Consolas;color:#1F497D'>BioAnalytical Lab Website:<o:p></o:p></span></u></b></p><p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas;color:#1F497D'>http://www.purdue.edu/discoverypark/bioanalytical/<o:p></o:p></span></p></div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> rasmb-bounces@rasmb.bbri.org [mailto:rasmb-bounces@rasmb.bbri.org] <b>On Behalf Of </b>Carlos Alfonso Botello<br><b>Sent:</b> Friday, July 20, 2012 11:17 AM<br><b>To:</b> rasmb<br><b>Subject:</b> [RASMB] proteins in water<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Dear colleagues,<br><br>We are running a 10 kDa protein at concentrations 0.2-2 mg/ml <b>in water</b> (no buffer is present).The sedimentation coefficients that we are obtaining are lower than expected for the monomer (1.4 - 1.5S). Is there any correction of the S that we could apply to obtain the correct S20,W.<br><br>Thank you in advance for your help,<br><br>Carlos<br><br><br><br><o:p></o:p></p><p style='margin-bottom:12.0pt'>Dr. Carlos Alfonso<br>Departamento Biologia Celular y Molecular<br>Laboratorio de Interacciones Macromoleculares: Bioquímica Citomimética<br>Centro de Investigaciones Biológicas, CSIC<br>C/ Ramiro de Maeztu, 9. <br>28040-MADRID<br>Tlfno.- 91 8373112 ext.4406-4408-4297 <br>Fax: 915360432.<br>E-mail: <a href="mailto:carlosa@cib.csic.es">carlosa@cib.csic.es</a><br><b>NEW lab web page: <br><a href="http://www.cib.csic.es/es/grupo.php?idgrupo=49">http://www.cib.csic.es/es/grupo.php?idgrupo=49<br></a></b><b><span style='font-size:24.0pt;font-family:Webdings;color:green'>P</span></b> <span style='font-size:7.5pt;font-family:"Tahoma","sans-serif";color:green'>Antes de imprimir este mensaje piense bien si es necesario hacerlo. El medioambiente es cosa de todos. <br>Please consider your environmental resposability before printing this e-mail.<br><br></span><o:p></o:p></p></div></body></html>