[RASMB] AUC reproducibility

[Karen Fleming]

Dear Mircea,

We also regularly repeat our experiments to obtain an experimentally 
determined standard deviation. We are not typically determining molar 
mass for a single ideal species. Rather we are typically determining a 
Monomer-Dimer equilibrium constant. For N=3-4 independent global 
experiments, we find that the stdev on this EQ constant is typically 
0.1-0.2 kcal mol-1. We, too, regard reproducibility as a requirement for 
publication of any analysis.

If your AUC results are not reproducible, I would argue that is a 
feature of (or problem with) the sample, not the AUC.
Hope this helps.
-Karen F.

pjgb at mrc-lmb.cam.ac.uk wrote:
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> Dear Mircea,
> 
> We regularly repeat analyses of aggregating macromolecular samples, 
> frequently from a different preparation, and find that the results are 
> reproduceable.  (Indeed, we regard this as a requirement for publication 
> of any analysis.)
> If they are not, I want to know why not, as it typically means that 
> some, previously unknown, factor is uncontrolled.
> 
> Yours,
> 
> Jo
> 
> --On Friday, April 1, 2005 8:01 pm +0200 "Rasa, M.V" <m.rasa at tue.nl> wrote:
> 
>> -------------------------------------------------------------------------
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>>
>> Dear colleagues,
>>
>> I am investigating now the reproducibility of measurements
>> of a sample prepared from the same supramolecular complex solution and
>> salt solution,
>> in ideal equilibrium runs and successive measurements (cells are
>> refilled after cleaning).
>> The whole procedure, including running parameters, is the same. Since I
>> obtained contradictory results,
>> I would like to ask you about your experience with reproducibility of
>> measurements with XL-A.
>> There are up to now no signs that something happened with our sample in
>> time (from wavelength scan measurements).
>> The chemical compatibility is also checked (well established already)
>> and preparation avoided
>> other polymers.
>>
>> Of course this is a general question, and I am very likely not aware of
>> all factors which may affect the result,
>> so I will come back with the necessary details according to your
>> comments.
>>
>> Thank you very much.
>>
>> Sincerely yours,
>>
>> Mircea Rasa.
>>
>> ____________________________________________
>>
>> Mircea RASA
>>
>> Eindhoven University of Technology
>> Faculty of Chemical Engineering and Chemistry
>> Laboratory of Macromolecular Chemistry and Nanoscience
>> PO Box 513, STO 3.39
>> 5600 MB Eindhoven, The Netherlands
>>
>> Tel: +31 (0)40 247 2835
>> Fax: +31 (0)40 247 4186
>> E-mail: m.rasa at tue.nl
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> 
> 
> 
> 
> P.J.G. Butler,
> MRC Laboratory of Molecular Biology,
> Hills Road, Cambridge, CB2 2QH, UK.
> Tel. +44 (0)1223 402296
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-- 
* * * * * * * * * * * * * * * * * * * * * * * * * * * *
Karen G. Fleming, Ph.D.
Assistant Professor
T. C. Jenkins Department of Biophysics
Johns Hopkins University
3400 North Charles Street
Baltimore, MD 21218

Karen.Fleming at jhu.edu
Voice: 410-516-7256
Fax:  410-516-4118
http://www.jhu.edu/~biophys/