Which of the following statements is true regarding how R groups affect -helix stability?
A. Adjacent, oppositely charged side chains can increase stability.
B. Due to its small size, glycine increases stability.
C. Bulky R groups create stabilizing van der Waals forces.
D. Since they are located on the exterior of the helix, R groups do not significantly alter stability.
E. None of these answers is correct.
Which of the following is least important for the binding of a protein to single-stranded DNA?
A. hydrophobic interactions between guanine and tyrosine
B. hydrophobic interactions between adenine and phenylalanine
C. attraction between phosphate groups and lysine
D. attraction between phosphate groups and arginine
E. hydrogen bonding between deoxyribose and tyrosine
In a solution at pH 7.0, a polymer of lysine (polylysine) is a random coil with no secondary structure. In order for it to possibly assume an -helix structure, the pH of the solution must be:
A. 4
B 6
C. 8
D. 10
E. 12
The Kd values of antibody-to-antigen binding range from 10-12 M to 10-8 M. Antibody X binds to wild-type E. coli ssDNA-binding protein, showing a value of Kd =10-11 M.
When antibody X binds to a mutant derived ssDNA-binding protein that contains a single amino acid substitution, a value of Kd = 10-7 M is determined. We can conclude that:
A. the amino acid substitution has increased the affinity of antibody X.
B. the amino acid substitution has decreased the affinity of antibody X.
C. the amino acid substitution has increased the affinity of ssDNA-binding protein to DNA.
D. the amino acid substitution has decreased the affinity of ssDNA-binding protein to DNA.
E. None of these choices is correct.
Which of the following amino acids would most likely not be found in an helix?
A. methionine
B. lysine
C. phenylalanine
D. proline
E. glutamine
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