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Unformatted text preview: [3 points] 2. What is the isoelectric point (pI) of oxytocin, which is shown below? Use the table in your book to locate the appropriate pKas. How many stereocenters are present on this molecule? In a different experiment, strong conditions have broken the disulfide bridge. Once this occurs, will the pI increase, decrease, or remain unaffected relative to its native pKa. Justify your reasoning [3 points] 3. Selenocysteine is shown below and the pKa of the side chain is 5.3. It is a naturally occurring unusual amino acid. Draw the titration curve for this amino acid between pH 0 - 14, and be sure to indicate where the isoelectric point lies (calculate pI to one decimal place). Make clear in your graph where half- and full equivalents of [ – OH] lie. Also, why would the pKa of selenocysteine be much lower than that of cysteine? [4 points]...
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This note was uploaded on 02/26/2010 for the course BIOCHEM CHEM1000 taught by Professor Hemstead during the Spring '09 term at York University.
- Spring '09