Protein Purification

Q1: Which of the following may be added to stabilize the protein after yeast cells disruption?

A NaCl

B Protease inhibitor

C AMP

D All of these

ANS:D - All of these

No answer description is available. 

Q2: A purified protein sample contains 10 μg of protein and has an enzyme activity of 1 m mole of ATP synthesized/sec (1 unit). What is the specific activity of the final purified sample?

A 1,000 units/mg

B 10,000 units/mg.

C 100,000 units/mg

D 1,000,000 units/mg

ANS:C - 100,000 units/mg

1 unit has been defined in the problem as 1 millimole synthesised per second.

It clearly says 10 microgram protein has one unit activity. So Specific activity is I unit/ 10 microgram protein and therefore it is 100units/mg.

This alternative is not given. Why should we change the given definition of the unit of enzyme in the problem?

Agreed that international definition of a unit is different.

Q3: Gel-filtration chromatography separates on the basis of

A size and shape using porous beads packed in a column

B size using porous beads packed in a column

C shape using porous beads packed in a column

D none of the above

ANS:A - size and shape using porous beads packed in a column

Gel permeation chromatography is known as size exclusion chromatography. And purifies the protein by moving through the pores in the beads, bigger size of peptides will move between the beads or will move through the coners as there size is more then the pore size of the beads. And small moleculez move through the pores in the beads and hence takes longer time to elute out, hence smaller the molecule slower the molecule. And shape also plays a very vital role here, if the shape is in such a way that the frictional force on it is less then it moves faster and if more then slower. And the answer should be A.

Q4: In ion-exchange chromatography

A proteins are separated on the basis of their net charge

B proteins are separated on the basis of their size

C proteins are separated on the basis of their shape

D either (b) or (c)

ANS:A - proteins are separated on the basis of their net charge

No answer description is available. 

Q5: Proteins separation can be carried out on the basis of

A net charge

B solubility in salt solutions

C size or mass

D all of these

ANS:D - all of these

Protein separation or protein purification is based the chromatography of affinity, gel filtration and ionic chromatography which are concernd with the solubility, size\mass and net charge in sequance.

Q6: During successful purification scheme, this may be expected that the

A specific activity increases

B specific activity decreases

C number of proteins in the sample decreases

D both (a) and (c)

ANS:D - both (a) and (c)

No.of proteins should decrease. then only we will be left with the protein of interest.

Specific activity = protein activity/ total mg of protein present.

So as we proceed towards more purification steps, we see increase in specific activity.

Q7: Affinity chromatography deals with the

A specific binding of a protein constituents for another molecule

B specific binding of a protein constituents for another molecule

C protein - protein interaction

D protein - carbohydrate interaction

E none of the above

ANS:A - specific binding of a protein constituents for another molecule

No answer description is available. 

Q8: The best way to determine the location of protein in the purification scheme is to measure the

A rate of ATP synthesis

B changes in the refractive index

C UV absorption

D mass spectroscopy of the protein

ANS:A - rate of ATP synthesis

I think the answer must be D to know if there still any more impurities still present, but answer c is correct to determine concentration of protein especially when purified in gel electrophoresis.



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