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Q5. B. (9 points, 3 fora protein with one cysteine residue wasn’t sure if it was functionally important or not.
She wanted to ‘block’ the 1 µM protein and 10 µM acetamide at pH (I-CH2 found that only 10% of the protein
Doing a test reaction with cysteine by reacting it with iodoacetamide 6, she CONH2). The reaction occurs only
when the sidechain of the period. She looked up a and displaces and found that the activation energy of the
had reacted over a 1 hour cysteine is deprotonated,similar reaction the iodide, making a bond to the CH2 was
acetamide. She wants to increase the reaction rate that a typical
≈80 kJ/mol. She checked her old textbook and found by 10 fold: 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 much would that protonation/deprotonation reactions acetamide to get the
How reminded hershe have to increase the concentration of are usually very rapid.10 fold...
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- Fall '09