Time Derivative Sedimentation Velocity Analysis


Figure 1. Plot of concentration versus radius

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Figure 2. Plot of time derivative vs radius

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Pairs of curves are subtracted at corresponding radial positions
to produce the baseline corrected time derivative pattern.

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Figure 3. Plot of averaged time derivative versus s*

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The x-axis for each of the curves from Figure 2 was transformed from radius to s* by the following relationship to compensate for the different times of sedimentation: This transforms the x-axis from the stationary reference frame of the ultracentrifuge cell to the moving reference frame of sedimentation.

where w is the angular velocity of the rotor
t is the sedimentation time
r is the radius, and
rm is the radius of the meniscus.

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Figure 4. Plot of g(s*) versus s*


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The y-axis of Figure 3 was transformed from dc/dt to g(s*) so that the area under each peak becomes equal to its (plateau) concentration.

Weight average s & other useful higher and lower order averages

Molar Mass Determination

Diffusion Coefficient Determination

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