Radius of the particle? Diffusion Problem

AI Thread Summary
The discussion centers on calculating the effective radii of proteins, specifically insulin and lysozyme, using the diffusion constant values provided for gel diffusion. The formula D = kT/(6πηR) is applied, with the viscosity set at 0.1 Pa•s and the temperature at 20ºC. Initial calculations yielded incorrect values for the radii, which were questioned for being too high. After re-evaluating, the correct effective radii were found to be 5.10 x 10^-12 m for insulin and 6.44 x 10^-11 m for lysozyme. The clarification that the values represent effective radii resolves confusion regarding the initial results.
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Homework Statement


One tool in analyzing proteins is gel diffusion. The technique is used to determine the size of the protein being analyzed. The following values are for diffusion through agarose gel.
D (m2/s)
Lysozyme 1.18E-10
BSA 3.90E-11
adolase 6.50E-11
Cu2+ 1.00E-10
glucose 2.90E-10
insulin 4.60E-10
The diffusion constant values are for the flux of particles, not change in concentration over time.





Treating the diffusing particles as spheres moving through a liquid which presents resistance or “drag”, the diffusion constant can be related to the effective particle radius as
D=kT/6πηR

Where k is Boltzmann’s constant, η is the viscosity, T is the temperature in Kelvin and R is the radius. Using 20ºC as the temperature and the above diffusion constants for insulin and lysosyme, Calculate the effective radii of the two proteins. An appropriate value for the viscosity is 100 centipoise = 0.1 Pa•s.

Do for Insulin and Lysozyme... Or just one i did them but i am not sure my answer is correct the seem to high.




Homework Equations



D=kT/6πηR

The Attempt at a Solution


These are the answers i got when i attempted the solution. They seem to big though?

Insulin i got R=1.9g x10^11

Lysozyme i got R=1.552 x 10^10

I just solved for R using the equation above
 
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I actually get 5.10x 10^-12 for insulin

and 6.44x 10^-11 for lysozyme


The other answers were 1/R not R

Is this correct because the are "effective"radius?
 

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