<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=iso-8859-15">
<META content="MSHTML 6.00.2900.3132" name=GENERATOR></HEAD>
<BODY style="MARGIN: 4px 4px 1px; FONT: 10pt Tahoma">
<DIV>Joy</DIV>
<DIV> </DIV>
<DIV>Sorry for the delay - classes are starting soon.</DIV>
<DIV> </DIV>
<DIV>When you fit for rates you often find very asymmetric error limits especially in the range where you approach very fast or very slow. In this case your best fit is on the edge of being fast and not kinetically mediated - thus values that are faster become indistinguishable from other vales & you see a wide error limit, often unbounded meaning you can't determine the error limit. The slower value is well determined and gives a narrow limit because this is distinguishing between very different kinetic profiles. </DIV>
<DIV> </DIV>
<DIV>You get the opposite asymmetry at the very slow limit where it is well limited on the faster side but indistinguishable or unbounded on the slower side. Said another way fast is fast and any value fits the data. Very, very slow is essentially nonexchangable between species and again you cannot determine a unique rate.</DIV>
<DIV> </DIV>
<DIV>The ability to fit for rates depends upon the quality of the data, the range of the data relative to Kd and the complexity of the system. For dimers the edge of the fast range is 5 x 10-3 and the edge of the slow range is 5 x 10-5.</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>-------------------------------------------------------------------<BR>Dr. John J. "Jack" Correia<BR>Department of Biochemistry<BR>University of Mississippi Medical Center<BR>2500 North State Street<BR>Jackson, MS 39216<BR>(601) 984-1522 <BR>fax (601) 984-1501 <BR>email address: jcorreia@biochem.umsmed.edu <BR>homepage location: <A href="http://biochemistry.umc.edu/correia.html">http://biochemistry.umc.edu/correia.html</A><BR>dept homepage location: <A href="http://biochemistry.umc.edu/">http://biochemistry.umc.edu/</A><BR>-------------------------------------------------------------------<BR><BR><BR><BR><BR>>>> On 8/9/2007 at 6:58 PM, in message <68e6eba10708091658h19a3ac73qcd13e814b8d71eaa@mail.gmail.com>, "Joy Zhao" <joyzhao@gmail.com> wrote:<BR></DIV>
<DIV style="PADDING-LEFT: 7px; MARGIN: 0px 0px 0px 15px; BORDER-LEFT: #050505 1px solid; BACKGROUND-COLOR: #f3f3f3">Hello everyone,<BR>I have a question about the error in determination of kinetic<BR>parameters by SedAnal. When I tried to fit my SV data to obtain kr (or<BR>kf) for a simple monomer-dimer system by using 2A-->A2 model, the<BR>error for the kinetic parameter seems big. I am wondering whether this<BR>is typical for the analyis by SedAnal.<BR><BR>(1).I was using F-statistics, Confidence Interval 68.27%. The rmsd of<BR>the fitting is 4.6771032.10-3 .<BR><BR>(2). This global fitting was performed with four data sets.<BR><BR>(3). Results: kr=0.00238 S-1 min=0.001138 S-1 max=0.099988<BR>S-1(CI=68.27%)<BR><BR>Thank you for your help!<BR><BR>Joy Zhao<BR>Dept of Chem and Biochem<BR>University of Maryland<BR>College Park,MD 20742<BR>_______________________________________________<BR>RASMB mailing list<BR>RASMB@rasmb.bbri.org<BR><A href="http://rasmb.bbri.org/mailman/listinfo/rasmb">http://rasmb.bbri.org/mailman/listinfo/rasmb</A><BR><BR><BR></DIV><br>
<br>
<br>
<br>
Individuals who have received this information in error or are not authorized to receive it must promptly return or dispose of the information and notify the sender. Those individuals are hereby notified that they are strictly prohibited from reviewing, forwarding, printing, copying, distributing or using this information in any way.
</BODY></HTML>