Problem 30
Gel-filtration chromatography is a useful method for removing salts, such as ammonium sulfate, from protein solutions. Describe how such a separation is accomplished.
Problem 32
What types of compounds make up the gels used in electrophoresis?
Problem 36
What does SDS-PAGE stand for? What is the benefit of doing SDS-PAGE?
Problem 38
Why is the order of separation based on size opposite for gel filtration and gel electrophoresis, even though they often use the same compound to form the matrix?
Problem 43
Why can the Edman degradation not be used effectively with very long peptides? Hint: Think about the stoichiometry of the peptides and the Edman reagent and the percent yield of the organic reactions involving them.
Problem 44
What would happen during an amino acid sequencing experiment using the Edman degradation if you accidentally added twice as much Edman reagent (on a per- mole basis) as the peptide you were sequencing?
Problem 46
A sample of a peptide of unknown sequence was treated with trypsin; another sample of the same peptide was treated with chymotrypsin. The sequences (N-terminal to C-terminal) of the smaller peptides produced by trypsin digestion were as follows: $$Met-Val-Ser Thr-Lys$$ $$Val-Ile-Trp-Thr-Leu-Met-Ile$$ $$Leu-Phe-Asn-Glu-Ser-Arg$$ The sequences of the smaller peptides produced by chymotrypsin digestion were as follows: $$Asn-Glu-Ser-Arg-Val-Ile-Trp$$ $$Thr-Leu-Met-Ile$$ $$Met-Val-Ser-Thr-Lys-Leu-Phe$$ Deduce the sequence of the original peptide.
Problem 48
You are in the process of determining the amino acid sequence of a peptide. After trypsin digestion followed by the Edman degradation, you see the following peptide fragments: $$Leu-Gly-Arg$$ $$Gly-Ser-Phe-Tyr-Asn-His$$ $$Ser Glu-Asp-Met-Cys-Lys$$ $$Thr-Tyr-Glu-Val-Cys-Met-His$$ What is abnormal concerning these results? What might have been the problem that caused it?
Problem 49
Amino acid compositions can be determined by heating a protein in \(6 M\) HCl and running the hydrolysate through an ion-exchange column. If you were going to do an amino acid sequencing experiment, why would you want to get an amino acid composition first?
Problem 53
What are the two principal types of mass spectrometry?
