Please help? These are 2 questions from my Physics II Lab, – Protein Gel Electro

Question

Please help? These are 2 questions from my Physics II Lab, – Protein Gel Electrophoresis. I'd appreciate your help a lot. Thanks.

4. In this experiment, we run the protein gels with a potential difference of 250V across the gel. Estimate the electric field (magnitude and direction) in the gel resulting from this potential difference. Note that we are using 8cm gels for this experiment.

5. Is it OK to ignore the force of gravity acting on the proteins in this experiment? Lets consider BSA, which has 583 amino acids, so (to one significant fig) binds approximately 200 SDS molecules according to the background presented in the Introduction. Each SDS carries a charge of 1e (-1.6x10-19 C). And as noted above, the mass of BSA in our buffer solution is approximately 62,000 Dalton. Using these values and your answer to number 4, calculate the ratio |Fg/FE| for a single BSA protein. Then comment, within the precision of your measurement, is it valid to neglect the force of gravity?

Explanation / Answer

electric field E = V/d

V is electric potential

d is distance

so

E = 250/0.08

E = 3125 V/m
----------------

yes

because F = Eq

and charge is of the order of 10^-19C

so

F will be in the order 10^-16 where g is just 9.8

so

Force of gravity can be ignroed on them

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