Some important biochemistry questions

1. The pK₁, pK₂, and pK_R of the amino acid lysine are 2.2, 9.1, and 10.5, respectively.  The pK₁, pK₂, and pK_R of the amino acid arginine are 1.8, 9.0, and 12.5, respectively.  A student wants to use ion exchange chromatography to separate lysine from arginine.  What pH is likely to work best for this separation?

2. What can be done to increase the rate at which a protein of interest moves down an ion-exchange chromatography column?

a) reduce the temperature of the eluant

b) aID a small amount of a non-ionic detergents to the eluant

c) reduce the ion concentration in the eluant

d) aID a protease inhibitor to the eluant

e) change the pH of the eluant

3. The peptide Leu?Cys?Arg?Ser?Gln?Met is subjected to Edman degradation.  In the first cycle the peptide first reacts with phenylisothiocyanate under basic conditions.  The product of this reaction is incubated with anhydrous trifluoroacetic acid and subsequently with an aqueous acid.  What are the products generated in the first cycle.

a) PTH?Leu, PTH?Cys, PTH?Arg, PTH?Ser, PTH?Gln, and PTH?Met

b) PTH?Leu?Cys and PTH?Arg?Ser?Gln?Met

c) PTH?Met and Leu?Cys?Arg?Ser?Gln?Met

d) PTH?Leu and Cys?Arg?Ser?Gln?Met

e) PTH?Leu?Cys?Arg?Ser?Gln?Met

4. What can be done to increase the rate at which a protein of interest moves down an ion-exchange chromatography column?

a) reduce the ion concentration in the eluant

b) aID a protease inhibitor to the eluant

c) reduce the temperature of the eluant

d) aID a small amount of a non-ionic detergents to the eluant

e) change the pH of the eluant

5. Which of the following changes would not alter the functional characteristics of ? keratin?

a) increasing the number of residues per turn to 4.1 while maintaining the same amino acid sequence

b) substitution of a hydrophilic amino acid for a hydrophobic amino acid at position a and d of the 7-residue pseudorepeat

c) decreasing the number of cysteine amino acids within each protofilament

d) changing the environment surrounding the protein to one that is more reductive

e) all of the above would alter the functional characterstics of keratin