HW%202%20Summer,%202008 - 1 of 3 Biological Sciences 102...

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1 of 3 Biological Sciences 102 Summer, 2008 K. Hilt Homework #2 1. Amino acid analysis is done on protein “Z”. However, in this case, the student decides to use an anion exchange resin, consisting of polystyrene covalently attached to a quaternary amine (the latter will be positively charged at all pH’s) to separate the amino acids. a) What is the minimum pH that the student should load the unknown amino acids onto this column? Show all calculations. b) What type of buffer should they use in the loading step? Describe the various factors that you should pay attention to when selecting a particular buffer for this experiment, and then select an actual compound, using appendix IV in “Biochemical Calculations”. If your buffer choice cannot satisfy all of the parameters that you have chosen, then mention what you would need to change in your experiment. c) Calculate how you would make up 1500 ml of a 0.10 M solution of your buffer, at the pH you chose in part “a” above, using the pK a you got from appendix IV, in part “b” above. 2. Let’s say that amino acid analysis of protein “Z” in question 1 above gave the following experimental results: Amino Acid Number of Residues in Protein “Z” Amino Acid Number of Residues in Protein “Z” A 13 B 13 G 12 W 6 P 5 H 12 Z 24 C 4 K 8 V 24 R 12 S 12 L 23 T 14 Y 12 F 13 a) What is the approximate net charge of protein “Z” at pH 7? Use the pK a ’s given in homework #1. Why is this net charge only an “estimate”? Discuss. b) What is the molecular weight of protein “Z”? Use the value of 110 Daltons as an average molecular weight of an amino acid residue. c) At pH 7, would you use a cation exchanger or anion exchange resin to bind protein Z, in order to do ion exchange chromatography? d) Does protein “Z” have quaternary structure? How would you experimentally confirm this?
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This note was uploaded on 10/19/2008 for the course BIS 102 taught by Professor Hilt during the Summer '08 term at UC Davis.

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HW%202%20Summer,%202008 - 1 of 3 Biological Sciences 102...

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