Question

Suppose you had a mixture of chymotrypsin (a monomer ,MW=23,000 , pI=9.5), albumin (a Monomer, MW= 68,500, pI=4.9) and hemoglobin (alpha2beta2 tetramer, MW=64,500, pI=7.0)

Which of the proteins would not bind to an anion exchange column at pH 8.2?

Which of these proteins would elute last from a gel filterartion (size exclusion) column?

Which protein would have the fastest migrating band on an SDS-PAGE gel, and Why?

Answer 1

1.Ans :- Chymotrypsin protein would not bind to an anion exchange column at pH 8.2

Explanation :-

pH of the resin is less than the pI of this Chymotrypsin protein. Therefore, Chymotrypsin protein bears a net positive charge. albumin and hemoglobin have pI less than the pH of the resin therefore they bear a net negative charge. so they do not bind to the anionic exchange resin.

2.Ans :- Chymotrypsin would elute last in the gel filtration.

Explanation :-

Because in gel filtration large molecules seep out through the gel beads faster on the other hand smaller proteins are trapped in the gel and therefore elute slowly.

3. Ans:- Hemoglobin protein would have the fastest migrating band on an SDS-PAGE gel.

Expalantion :-

SDS-PAGE is used to denature a protein and electrophorese the component monomers. Hemoglobin is composed of four monomers and during electrophoresis these monomers migrate faster because the molecular weight of individual monomers of hemoglobin is less as compared to the monomers of other two proteins. therefore Hemoglobin protein would have the fastest migrating band on an SDS-PAGE gel.