She checked her old textbook and found that a typical

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Unformatted text preview: points total) A researcher studying a protein with one cysteine residue wasn’t sure if it was functionally important or not. She wanted to ‘block’ the cysteine by reacting it with iodoacetamide (I-CH2CONH2). The reaction occurs only when the sidechain of the cysteine is deprotonated, and displaces the iodide, making a bond to the CH2 of the acetamide. She checked her old textbook and found that a typical pKA value for cysteine is 8.3 at 25° C, and identified a simple colorimetric assay to determine the extent to which the cysteine was modified. Her reading also reminded her that protonation/deprotonation reactions are usually very rapid. v( •  v( Q5. A. (6 points) Write a kinetic scheme and corresponding differential equation that describes the rate of formation of modified protein with time as a function of the concentration of protein and acetamide present in the solution, and any other needed parameters. Q5. B. (9 points, 3 for each part) Doing a test reaction with 1 µM protein and 10 µM acetamide at pH 6, she found that only 10% of the protein had reacted over a 1 hour period. She looked up a similar reaction and...
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