Theme 2.2

Proteins are synthesized in vivo by the translation of

Since there are 20 standard amino acids, the number of possible linear polypeptides of length N can be expressed as:

Natural proteins most commonly contain linear polypeptides between 100 and 1000 residues in length. One of the reasons

The vast majority of polypeptides contain between ______ amino acid residues.

Which of the following has the most dramatic influence on the characteristics of an individual protein?

Which statement about insulin is correct?

The salting in of proteins can be explained by:

The quantitation of proteins due to their absorbance at ~280 nm (UV region) is due to the large absorbtivity of the ________ amino acids

Which of the following ‘assays’ would be most specific for a particular protein?

An enzyme-linked immunosorbent assay requires

ELISA is an example of a(n):

You are purifying a nuclease by affinity chromatography. To determine which fractions contain the protein of interest, you test samples of all fractions for their ability to break down DNA. This is an example of

A radioimmunoassay requires

Five graduate students prepare extracts from 5 different tissues. Each student measures the total amount of alcohol dehydrogenase and the total amount of protein in his or her extract. Which extract has the highest specific activity?

Total protein (mg) Total alcohol dehydrogenase activity (units)
A 300 60,000
B 200 80,000
C 3000 96,000
D 5000 100,000
E 1000 200,000

Which physical characteristic is not commonly used in protein separation?

Adding additional salt to a protein solution can cause:

A first step in purifying a protein that was initially associated with fatty substances would be

The acronym HPLC stands for

A technique that can be used to separate proteins based primarily on the presence of non-polar residues on their surface is called

A technique that can be used to separate proteins based primarily on their pI is called

Which of the following amino acids would be last to elute at pH 8.0 from an anion-exchange column?

Which of the following amino acids would be first to elute at pH 8.0 from an anion-exchange column?

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

The pK1, pK2, and pKR of the amino acid histdine are 1.8, 9.3, and 6.0, respectively. The pK1, pK2, and pKR of the amino acid arginine are 1.8, 9.0, and 12.5, respectively. You have a mixture of histidine and arginine, how would you try to separate these two amino acids?

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

Hydrophobic interaction chromatography can be used to separate proteins based on differences in

You are trying to separate five proteins, which are listed below, by gel filtration chromatography. Which of the proteins will elute first from the column?

SDS-PAGE separates proteins primarily due to differences in

Which of these techniques is used to separate proteins mainly based on mass?

Which of these techniques uses antibodies to detect very small amounts of specific proteins following separation by SDS-PAGE.

Disulfide bonds can be cleaved using

Which of these reagents is commonly used to determine the number of polypeptides in a protein?

Enzymes that hydrolyze the internal peptide bonds (not the peptide bonds of the terminal amino acids) of a protein are classified

Which of the following substances cannot be used to cleave peptide bonds in polypeptides?

Which of these are commonly used to cleave peptide bonds in polypeptides?

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.

Edman degradation can be used to

Although a protein’s primary sequence can be inferred from the nucleotide sequence, modifications such as ______ can be determined most easily by tandem mass spectrometry followed by protein database searching.

The positive charge on proteins in electrospray ionization mass spectrometry is the result of

______________ has emerged as a technique for protein sequencing.

Protein sequences are customarily ‘reconstructed’ from sequenced fragments because

You have purified a new peptide hormone. To determine its amino acid sequence you have digested the polypeptide with trypsin and in a separate reaction you have cleaved the polypeptide with cyanogen bromide.

Cleavage with trypsin yielded 5 peptides that were sequenced by Edman degradation as shown in the following.
1. Ser─Leu
2. Asp─Val─Arg
3. Val─Met─Glu─Lys
4. Ser─Gln─Met─His─Lys
5. Ile─Phe─Met─Leu─Cys─Arg

Cleavage with cyanogen bromide yielded 4 peptides that were sequenced by Edman degradation:

1. His─Lys─Ser─Leu
2. Asp─Val─Arg─Val─Met
3. Glu─Lys─Ile─Phe─Met
4. Leu─Cys─Arg─Ser─Gln─Met

Determine the identity of the N-terminal amino acid after reconstructing the intact protein.

In two homologous proteins, which residue is most likely to replace a Glu residue as a conservative substitution?

A phylogenetic tree depicts ___________ of proteins.

A protein that has had few changes in its amino acid sequence over evolutionary history is labeled

Paralogous genes are

A fast way for nature to generate new proteins is:

___________ is an example of a very slowly evolving protein.

Proteins are often constructed from multiple segments of 40-200 amino acid residues, commonly called

In a conjugated protein, a prosthetic group is: