[RASMB] Protocol for Gravitational Sweep Sedimentation Velocity Study

[QCZ]

James,
You need to use the protocol for SE to collect data at various speeds and
analyze by Sedanal or dc/dt.

Qin (Chin) Zou, Pfizer Inc.


On 5/5/09, Falabella, James <james.falabella at nist.gov> wrote:
>
>  Dear RASMB Members,
>
>
>
> I am performing sedimentation velocity to examine the particle size
> distribution of 10 nm diameter gold particles that I have intentionally
> induced into stable aggregates. I suspect that the aggregates population
> ranges from dimers to tetramers. At first, I tried to sediment the
> aggregated particles at 7000 RPM in an XL-A outfitted with: 4-hole ANTI60
> rotor, 12 mm charcoal-Epon cells, quartz windows and the absorbance scans at
> 520 nm (with the 400 nm filter in the light path) appeared mal-formed while
> the scans of another cell with the non aggregated 10 nm diameter gold
> particles are well formed sigmoids and easily fit by Sedfit. I looked up
> some references from the literature on the analysis of wide distribution
> samples with an analytical ultracentrifuge that were very good background,
> however, they did not have a protocol that spelled out what buttons to press
> to get the XL-A to collect the data at different angular velocities. I went
> ahead with my centrifugation study by performing several back to back runs
> where I simply started run after run using the Beckman software to increase
> the rotor speed from 3000 to 5000 to 8000 RPM, however, the 5000 and 8000
> RPM runs could not be fit by Sedfit due to the fact that there was not a
> long enough acceleration phase from one speed to the next.  I looked through
> Sedfit and could not find a way to get around this error and it is probably
> not a good idea to try my own fix before asking around for any tips on how
> to address the proper operation of the XL-A for a gravitational sweep and
> data analysis.
>
>
>
> Thank you in advance for your advice,
>
>
>
> James Falabella
>
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>
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