Chapter 5

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One of the reasons the primary structure is important for a protein is that it determines the the molecule adopts in aqueous solutions. A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

D

If the cDNA for a protein has been cloned, it may be possible to obtain large quantities of the protein by........in bacteria A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

J

To help prevent denaturation of proteins in solution, steps are taken to avoid and adsorption to surfaces. A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

I

Molecules that contain a(n) are capable of absorbing light. A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

H Signup and view all the answers

If antibodies to the protein being assayed are available, a(n) can be carried out. A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

C Signup and view all the answers

In general, proteins are least soluble in water when the pH is close to the A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

N Signup and view all the answers

......chromatography is a method of fractionating a protein mixture according to differences in polarity. A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

B Signup and view all the answers

In order for DEAE to act as an anion exchanger, it must have a A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

L Signup and view all the answers

In chromatography, a protein mixture must be applied to the column at a low pH so that the proteins will have a net positive charge and bind to the column. A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

M Signup and view all the answers

In SDS-PAGE, disulfide-linked polypeptides can be separated after reacting the protein first with . A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

K Signup and view all the answers

Either dansyl chloride or Edman's reagent can be used to identify the of a proteinA) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

E Signup and view all the answers

The endoprotease cleaves polypeptides on the C-terminal side of certain bulky hydrophobic amino acid residues. A) electrophoresis B) hydrophobic interaction C) enzyme-linked immunosorbent assay D) three-dimensional shape E) N-terminal amino acid F) negative charge G) nucleases H) chromophore I) foaming J) high level expression K) 2-mercaptoethanol L) positive charge M) cation exchange N) pI O) chymotrypsin P) C-terminal amino acid Q) Sodium dodecyl sulfate

O Signup and view all the answers

Proteins are synthesized in vivo by the translation of

mRNA Signup and view all the answers

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

20^n Signup and view all the answers

Natural proteins most commonly contain linear polypeptides between 100 and 1000 residues in length. One of the reasons polypeptides outside this range may be disfavored is that

smaller polypeptides do not form stable folded structures. Signup and view all the answers

The vast majority of polypeptides contain between amino acid residues.

100 and 1000 Signup and view all the answers

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

the amino-acid sequence Signup and view all the answers

Which statement about insulin is correct?

All of the above are correct. Signup and view all the answers

A fast and common method for determining the protein concentration in column effluent is

measuring light absorption at 280 nm. Signup and view all the answers

The salting in of proteins can be explained by:

salt counter-ions reducing electrostatic attractions between protein molecules. Signup and view all the answers

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

aromatic Signup and view all the answers

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

radioimmunoassay Signup and view all the answers

An enzyme-linked immunosorbent assay requires

an antibody that binds the protein of interest. Signup and view all the answers

ELISA is an example of a(n):

immunological assay. Signup and view all the answers

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

an enzyme assay. Signup and view all the answers

A radioimmunoassay requires

a radiolabeled standard protein that is used to compete for binding to the antibody. Signup and view all the answers

Which physical characteristic is not commonly used in protein separation?

stereochemistry Signup and view all the answers

Adding additional salt to a protein solution can cause:

all of the above Signup and view all the answers

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

hydrophobic interaction chromatography. Signup and view all the answers

The acronym HPLC stands for

high performance liquid chromatography. Signup and view all the answers

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

hydrophobic interaction chromatography. Signup and view all the answers

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

isoelectric focusing. Signup and view all the answers

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

glutamic acid Signup and view all the answers

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

lysine Signup and view all the answers

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

change the pH of the eluant Signup and view all the answers

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

polarity. Signup and view all the answers

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?

glutamine synthetase (621 kDa) Signup and view all the answers

SDS-PAGE separates proteins primarily due to differences in

mass. Signup and view all the answers

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

SDS-PAGE Signup and view all the answers

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

immunoblotting Signup and view all the answers

Disulfide bonds can be cleaved using

2-mercaptoethanol (-ME). Signup and view all the answers

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

dansyl chloride Signup and view all the answers

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

endopeptidases. Signup and view all the answers

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

endopeptidases Signup and view all the answers

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

trypsin Signup and view all the answers

Edman degradation can be used to

identify the N-terminal amino acid of a polypeptide. Signup and view all the answers

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.

all of the above Signup and view all the answers

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

protonated side chains of Arg and Lys residues. Signup and view all the answers

has emerged as a technique for protein sequencing.

NMR spectroscopy Signup and view all the answers

Protein sequences are customarily ‘reconstructed’ from sequenced fragments because

large polypeptides cannot be directly sequenced. Signup and view all the answers

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.

Ser─Leu

Asp─Val─Arg

Val─Met─Glu─Lys

Ser─Gln─Met─His─Lys

Ile─Phe─Met─Leu─Cys─Arg Cleavage with cyanogen bromide yielded 4 peptides that were sequenced by Edman degradation:

His─Lys─Ser─Leu

Asp─Val─Arg─Val─Met

Glu─Lys─Ile─Phe─Met

Leu─Cys─Arg─Ser─Gln─Met Determine the identity of the N-terminal amino acid after reconstructing the intact protein.

Asp Signup and view all the answers

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