Chem 271 - Midterm 1 - Chem 271/MCB 212: First Midterm...

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Unformatted text preview: Chem 271/MCB 212: First Midterm February 26 st , 2009 Please provide all answers in the space provided. Extra paper is available if needed. No calculators or molecular model kits may be used for this exam. Including the title page, there should be 8 pages in this booklet. Good Luck! Name ___________________________________________(2 points) (1) _____________ (16 points) (2) _____________ (20 points) (3) _____________ (18 points) (4) _____________ (20 points) (5) _____________ (24 points) TOTAL _____________ (100 points) 1. Cysteine residues provide some of the most reactive functional groups that occur in proteins. The following questions relate to the structure and modification chemistry of this residue (4 points each, 16 points total). a) In the space below, provide the full structure of a cysteine residue as it would be found in a polypeptide chain. Be sure to indicate the correct stereochemistry and provide an accurate value for the pK a of the side chain group. b) Provide the specific chemical structure of a reagent that would lead to the irreversible modification of this residue. Also provide the product of your modification reaction. c) Give an example of a reagent that would lead to the modification of this residue, yielding a structure that could be cleaved from the protein in a later step. Also provide the product of the first step of your modification reaction. d) Before most proteins can be analyzed by gel electrophoresis, all of the disulfides in the protein must be reduced. List two reagents that could be used to do this and include a structure for one of them. 2. Amino acid 1 has been incorporated into proteins using the Schultz in vitro method. a) Starting with the amino acid, briefly outline the steps that you would take to accomplish this. You do not have to list specific reagents or any protecting groups; just provide a general description of each step in the process. For the purposes of this question, assume that the artificial amino acid is not toxic and that all of the functional groups are stable in living cells (5 points)....
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This note was uploaded on 02/19/2010 for the course CHEM 271 taught by Professor Mattfrancis during the Spring '09 term at University of California, Berkeley.

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Chem 271 - Midterm 1 - Chem 271/MCB 212: First Midterm...

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