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<DIV>Jack</DIV>
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<DIV>S values are typically only reproducible to a +/- 0.5% average anyway. But it might be useful to do a global fit with say Sedanal and then an Fstat error bar on the average value, with and without floating rm values. We certainly see wavelength dependent and optical system variation in assigning rm values. But systematic variation by cell 1,2,3, which I presume means position 1,2,3 in a 4 hole rotor, is unusual. I do see reproducible variation in a six hole rotor but that is variation by radial position, low, medium, vs high radius. Each velocity cell should see the same light intensity. Do you get the same result if cell 1 is placed in hole 2 or 3? Is it the cell meaning a defect in a cell which may mean convection or is it cell position?</DIV>
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<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: <A href="mailto:jcorreia@biochem.umsmed.edu">jcorreia@biochem.umsmed.edu</A> <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>>>> "jack kornblatt" <krnbltt@vax2.concordia.ca> 08/08/06 4:07 PM >>><BR></DIV>
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<DIV><FONT face=Arial size=4>I have recently come across a problem the answer to which I cannot find in the Archives.</FONT></DIV>
<DIV><FONT face=Arial size=4>The problem is this: If I run the same sample in the AUC at the same temperature and speed over the course of 5 days, I get a distribution of s values that has a spread of plus or minus <0.4%. The sample is quite stable and shows no suggestion of degradation between days 1 and 4 but a small peak (< 2% of the total) shows up on day 5. The perplexing thing is that there are systematic differences between cells 1, 2 and 3. The s values in cell 1 are always highest, the s values in cell 2 are lowest and the s values in cell 3 intermediate. The differences are small. Cell 1 s values are about 0.4% less than those of cell 1. </FONT></DIV>
<DIV><FONT face=Arial size=4>The samples in the three cells are the same; they were taken from the same batch. The buffer is the same. </FONT></DIV>
<DIV><FONT face=Arial size=4>The problem has only become evident recently. It was not present two years ago but I cannot state unequivocally when it first started to occur.</FONT></DIV>
<DIV><FONT face=Arial size=4>Has anyone suggestions as to cause and what might be done to correct the problem?</FONT></DIV>
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<DIV><FONT face=Arial size=4>thanks for any help you can give</FONT></DIV>
<DIV><FONT face=Arial size=4>jack (kornblatt)</FONT></DIV></DIV></BODY></HTML>