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  Native protein purifications often require multiple reaction steps in order to purify the protein of interest from other proteins

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1. Native protein purifications often require multiple reaction steps in order to purify the protein of interest from other proteins. One method used for protein separation in purification procedures is a change from water to an organic solvent. Which of the following would be accomplished by this solvent change?
   A. Proteins with hydrophobic groups on the interior would maintain their native state.
   B. Proteins with hydrophilic groups on the exterior would denature and likely precipitate.
   C. Proteins with exposed hydrophobic groups would maintain their structure and remain in solution.
   D. Both A and B would occur.
   E. Both B and C would occur.
2. Which of the following amino acids would be first to elute at pH 8.0 from an anion-exchange column?
   A. Alanine
   B. Glycine
   C. glutamic acid
   D. asparagine
   E. lysine
3. Imagine that a researcher treated a protein with a high concentration of a chaotropic agent. Which of the following is the most likely result of the treatment?
   I Nonpolar portions of the protein become more soluble.
   II. The protein begins to denature ,
   III. The protein stability increases due to hydrophobic collapse,
   A. I, II, III
   B. I, II
   C. II, III
   D. I, III
   E. II
4. Which of the following lines in the figure at right indicates a b hairpin structure?
   A. A, C, D
   B. B and C
   C. A only
   D. A, B, and D
   E. C only
5. While proteins are usually composed of linear chains of amino acids, branched chains of amino acids and internally cross-linked chains can be found in certain proteins. Polypeptide chains are most commonly linked to each other through
   A. glycosidic bonds
   B. hydrogen bonds.
   C. disulfide bonds.
   D. peptide bonds.
   E. ester linkages
6. For b-sheets, the terms 'parallel' and 'antiparalllel' refer to ___________.
   A. the quaternary structure of the protein
   B. the topology of the reverse turns
   C. the orientation of the hydrogen bonding
   D. the 'direction' of the associated peptide strands
   E. the orientation of the amide cross-links
7. Ribosomes use L amino acids to synthesize proteins. These amino acids are called "L" because
   A. they turn polarized light to the left.
   B. they have a configuration of groups around the Ca that can be related to the configuration of groups around the asymmetric carbon in L-glyceraldehyde.
   C. they are all (S)-amino acids.
   D. they are chiral.
   E. they are all (R)-amino acids
8. Noncovalent forces that stabilize protein structure include all of the following except __________.
   A. the hydrophobic effect
   B. disulfide bridges
   C. salt bridges
   D. hydrogen bonding
   E. electrostatic interactions with metal ions