p1_S07ANSPOST - Prelim regrade requests must be submitted...

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Prelim regrade requests must be submitted in writing to Shirley Soule (217 Stimson) no later than 2:00 PM on Friday 3/30. 1. a. (4 points) Draw the complete structure of arginine at pH 7.0. (Nelson & Cox, Fig. 3-5, p. 79) b. (1 point) Name the functional group in arginine. (Nelson & Cox, Fig. 1-15, p. 14) guanidino c. (2 points) Give the one and three letter abbreviations for arginine. One letter abbreviation: R Three letter abbreviation: Arg d. (3 points) Calculate the isoelectric point of arginine (Show all work!). (12.5 + 9)/2 = 10.75 2. a. (1 point) Describe the structural feature that makes proline unique. (Nelson & Cox, p. 79) The side chain of proline is covalently bonded to its amino terminus. b. (2 points) Give two reasons why proline is typically found on the surface of a protein whereas based on its hydrophobic character one would expect it to be buried. (Nelson & Cox, p. 122) 1) Because the backbone is bonded to the side chain, proline residues are less flexible and are usually excluded from secondary structures in globular proteins. 2) In a polypeptide, the proline amino group lacks hydrogen and therefore the presence of proline interferes with the regular, repeating backbone hydrogen bonds typical of secondary structures. (also acceptable - 1) proline is excluded from secondary structures and 2) found in turns)
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BioBM 330 prelim 1, Spring '07 Name: ___________________________ 2 3. a. (3 points) Describe the process by which a random coil polypeptide is converted to the molten globular state. Include in your answer the most important interaction in the process as well as the driving force . Linear polypeptides are driven to fold thermodynamically to minimize free energy. The main driving force in the initial stages of folding are hydrophobic interactions that drive the hydrophobic side chains into the core of the protein (away from contact with the aqueous environment). (3 points) Why is it important for 2° structures to form during the formation of the molten globular state? (Study Guide, unit 2, page 9, objective 12. b. 1))Prior to folding, peptide bonds in the polypeptide backbone are polar and are stabilized by hydrogen bonding with water. In the core of the protein, the hydrogen bonds to water are replaced with intramolecular hydrogen bonds in secondary structures. b. In the 1950's Anfinsen and his coworkers proved that the 1° sequence of a polypeptide determines its 3° structure by demonstrating that reduced and denatured RNase was able to refold to native, enzymatically active form. (1 point) In order to recover full RNase activity, Anfinsen et al found it necessary to add a small amount of a reducing agent, 2-mercaptoethanol, during the refolding process. Explain how this addition facilitated folding to the native form. During folding in an oxidizing environment, whenever two
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p1_S07ANSPOST - Prelim regrade requests must be submitted...

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