[RASMB] s20w calculation

[Lake Paul]

John,
I would calculate it manually:
Eqn is S20W = s[(1-v*rho20W)/(1-v*rhoexperimental)*[nexperimental/n20W)

Here is the link to that equation:
http://bitcwiki.sr.unh.edu/index.php/Converting_s_to_s-20-w   (SEDNTERP)

When in doubt, don't trust HAL! :)

Lake



On Thu, Aug 8, 2013 at 8:38 PM, John Sumida <jpsumida at u.washington.edu> wrote:
> Dear RASMB
>
>
>
> Wondering about the s020w calculation in SEDNTERP
>
>
>
> For one of our polymer micelles with which we’ve been working, a SEDANAL
> analysis returns an s20w value (not corrected for concentration) of 17.3.
>
>
>
> If I use equation 19 in cited in the SEDNTERP documentation, from the s20w
> value=17.3, I calculate s* = 16.4s.
>
> Phsyical parameters used:
>
> 1.     experiment temp=20oC,
>
> 2.     vbar=0.8312 (measured by densitometry at 20oC)
>
> 3.     density of solution 1.00506 gms/cm3 (measured)
>
> 4.     viscosity 0.010281 (measured)
>
> 5.     Assuming viscosity of water to be 0.01002, and the density to be
> 0.998234
>
>
>
> However if I use the Experiment page in the SEDNTERP and enter value of s*
> calculated above, then s20w returned is 27.8 which is much higher than the
> value returned from SEDANAL.  In fact in order to get SEDNTERP to return a
> value of 17.3s, I have to decrease S* to be 2.91s.
>
>
>
> In SEDFIT, if I input 16.4s, calculated from Equation 19 in the SEDNTERP
> documentation, and input the same physical parameter listed above, I get
> 17.4s in agreement with the SEDANAL result.
>
>
>
> I think in both SEDNTERP and SEDFIT, the same equation is used to correct s*
> to s20w, so I’m not clear what I’m missing.
>
>
>
> Any suggestions and comments are welcome and thank you, in advance, for
> taking the time to consider my question.
>
>
>
> Best regards,
>
>
>
> John Sumida
>
> Analytical Biopharmacy Core Facility
>
> University of Washington
>
> Molecular Engineering & Sciences Institute, G22
>
> 3946 West Stevens Way NE
>
> Seattle WA 98195-1653
>
>
>
>
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>



-- 
Lake Paul, PhD
Facility Director

Biophysical Analysis Lab
Purdue Proteomics Facility

Bindley Bioscience Center
Purdue University
1203 West State Street,
West Lafayette, Indiana, 47095
765.494.4960