Key HW 2 Summer 2010

Key HW 2 Summer 2010 - 1 of 3 Biological Sciences 102...

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1 of 3 Biological Sciences 102 Answer Key Summer, 2010 K. Hilt Homework #2 1. Amino acid analysis is done on protein “Z”. The following results are obtained: 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) Calculate the net charge, to the nearest 0.01, of protein “Z” at pH 7. Use the pK a ’s given in homework #1. “–16.4” Use the pK a ’s of 7.4 and 3.6 for the N- and C-termini. The charge coming from lysines in protein Z would be +8. 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. 22,770 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? anion exchanger d) Does protein “Z” have quaternary structure? How would you experimentally confirm this? We do not know, from the information given above. What would you propose to find out? 2. In the table of question #1 above, there are no NH 4 + ions listed. What does that tell you about B and Z in the table? It says that B is D and Z is E. Both D and E will contribute one negative charge per residue at pH 7. If there had been 8 NH 4 + ions in the above table, what would you have concluded? There would have been some combination of N and Q that added up to 8. Would the calculated net charge of protein Z change? If so, what is the new value?
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Key HW 2 Summer 2010 - 1 of 3 Biological Sciences 102...

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