Due Monday 4/26/04 at lectureChapter 8: Problems # 7, 19, 21, & 22ProcedureProblem set # 3 Chemistry 153A-2 Spring 2004 Due Monday 4/26/04 at lecture • It is a very good idea to try all the problems listed. • Turn in only the problems marked with an * for grading (#2, #6, and #8) From your text book: Chapter 4: Problems # 1, 2, 3, 4, 5 & 9 Chapter 6: Problems # 1, 3, 4, 5, 6, & 8 Chapter 7: Problems # 1, 2, 3, 4, & 5 Chapter 8: Problems # 7, 19, 21, & 22 1. Draw the peptide ATLDAK. Name the above peptide. What is its net charge at pH 7.0? *2. Calculate the pH of a 0.1 M solution of glycine hydrochloride. 3. Draw the structure of glutamylserylglutamylvaline. Sketch the pH curve for the titration of 1 mole of glutamylserylglutamylvaline hydrochloride. Calculate the pI for this peptide. 4. Determine the net charge of the predominant form of Asp at a) pH 1, b) pH 3, c) pH 6, and d) pH 11. 5. Draw the dipeptide Asp-His at pH 7.0 *6. Determine the subunit composition of a protein from the following information: Molecular mass by gel filtration: 300 kD Molecular mass by SDS-PAGE: 150 kD Molecular mass by SDS-PAGE with 2-mercaptoethanol: 50 kD, 100 kD Explain your reasoning. 7. Cleavage of a polypeptide by CNBr and chymotrypsin yields fragments with the following amino acid sequence. What is the sequence of the intact polypeptide? CNBr treatment Arg-Ala-Tyr-Gly-Asn Leu-Phe-Met Asp-MetProblem set # 3 Chemistry 153A-2 Spring 2004 Chymotrypsin Met-Arg-Ala-Tyr Asp-Met-Leu-Phe Gly-Asn *8. A) The octapeptide AVGWRVKS was digested with the enzyme trypsin. Would ion exchange or size exclusion be most appropriate for separating the products? Explain. B) Suppose that the peptide was digested with chymotrypsin. What would be the optimal separation technique? 9. Amino acid analysis of an oligopeptide seven residues long gave Asp Leu Lys Met Phe Tyr The following facts were observed: a) Trypsin treatment had no effect b) The phenylthiohydantoin released by Edman degradation was a Phe derivative. c) Brief chymotrypsin treatment yielded several products, including a dipeptide and a tetrapeptide. The amino acid composition of the tetrapeptide was Leu, Lys, and Met. d) CNBr treatement yielded a dipeptide, a tetrapeptide and a free Lys. What is the amino acid sequence of this heptapeptide? 10. You performed a protein purification procedure involving several steps. The steps are shown in chronological order. Procedure Total activity (µmol/min) Total Protein (mg) Specific activity %F Yield old Purification Homogenate 10005 1002 Step 1 9650 520 Step 2 6009 410 Step 3 4001 31Problem set # 3 Chemistry 153A-2 Spring 2004 Step 4 2020 11 a) Complete the purification table. b) Show a sample calculation for specific activity, % yield and fold purification. c) Which “Step” was the most effective step in the purification? Why do you say
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