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Biochemistry

BioTutorial 253

Biochemistry

Gel Electrophoresis Quiz
The figure below shows an SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) gel. The proteins have been stained with Coomassie Blue dye.
 Five different samples were run on this gel:
  1. A total cell lysate.
  2. After salt precipitation with ammonium sulfate.
  3. After chromatography on column "A".
  4. After chromatography on column "B".
  5. Purified material (band C) with two molecular weight standards, A and B:
Standard Molecular
Weight		 Log(MW)
A 100,000 5
B 10,000 4

Q1: What type of chromatography was used for column "A"?

Q2: What is the molecular weight of the purified protein?

Q3: Is this molecular weight necessarily the molecular weight of the functional protein?

Answers:

Q1: Most likely gel filtration chromatography because proteins of a similar size were selected.

Q2: If log(MW) = 5 corresponds to a migration of 2cm, and log(MW) = 4 corresponds to a distance of 8 cm, then 10 cm (the distance migrated by C), is log(MW) = 3.66, or a molecular weight of about 4,500 Da.

Q3: No, since this is a denaturing gel the protein may function as a dimer, trimer, tetramer, etc.


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March 21, 2001

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