The most important contribution to the stability of a protein’s folded conformation appears to be the:

1. free energy difference between the ordered water molecules in the solvent shell around folded protein vs the solvent shell of other polypeptide conformations.
2. entropy increase from ionic interactions between the ionized amino acids in a protein.
3. sum of free energies of formation of many weak interactions among the hundreds of amino acids in a protein.
4. sum of free energies of formation of many weak interactions between its polar amino acids and surrounding water.
5. stabilizing effect of hydrogen bonding between the carbonyl group of one peptide bond and the amino group of another.

Pauling and Corey’s studies of the peptide bond showed that:

1. at pH 7, many different peptide bond conformations are equally probable.
2. peptide bonds are essentially planar, with highly restricted rotation about the C—N axis.
3. peptide bonds in proteins are unusual, and unlike those in small model compounds.
4. peptide bond structure is extraordinarily complex.
5. primary structure of all proteins is similar, although the secondary and tertiary structure may differ greatly.

Roughly how many amino acids are there in one turn of an α helix?

1. 1
2. 2.8
3. 3.6
4. 4.2
5. 10

Which of the following amino acid configurations would most destabilize an α helix:

1. a negatively charged Arg residue.
2. a nonpolar residue near the carboxyl terminus.
3. a positively charged Lys residue.
4. a Pro residue.
5. two Ala residues side by side.

Hydrogen bonds in β strands are ____ hydrogen bonds in α helices

1. stronger than
2. weaker than
3. more likely to connect distant peptide sequences
4. more likely to connect adjacent peptide sequences
5. more likely to involve side chain donors and acceptors

Kendrew’s studies of the globular myoglobin structure demonstrated that:

1. “corners” between α-helical regions invariably lacked proline residue.
2. highly polar or charged amino acid residues tended to be located interiorally.
3. myoglobin was completely different from hemoglobin, as expected.
4. the structure was very compact, with virtually no internal space available for water.
5. the α helix predicted by Pauling and Corey was not found in myoglobin.

Analysis of x-ray diffraction data yields a(n)____________ ; analysis of 2D NMR data yields a(n) ____________ .

1. electron density map; count of hydrogen atoms in the molecule
2. shadow of protein’s outline; estimate of protein’s molecular volume
3. table of interatomic distances; electron density map
4. electronic density map; table of interatomic distances
5. 3-d protein structure; 2-d protein structure

Which of the following statements concerning protein domains is true?

1. They are a form of secondary structure.
2. They are examples of structural motifs.
3. They consist of separate polypeptide chains (subunits).
4. They have been found only in prokaryotic proteins.
5. They may retain their correct shape even when separated from the rest of the protein.

Which of the following is least likely to result in protein denaturation?

1. Altering net charge by changing pH
2. Changing the salt concentration
3. Disruption of weak interactions by boiling
4. Exposure to detergents
5. Mixing with organic solvents such as acetone

Which of the following statements concerning the process of spontaneous folding of proteins is false?

1. It may involve a statistical search of all possible chain configurations.
2. It may be defective in some human diseases.
3. It may involve a gradually decreasing range of conformational species.
4. It may involve initial formation of a highly compact state.
5. It may involve initial formation of local secondary structure.