Problem_Set_11 - Chem 358 - Spring 2009 Problem Set 11...

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Chem 358 - Spring 2009 Problem Set 11 Chapter 22: 46-49, 53, 56, 57, 63 Additional problems on amino acids and peptides Amino acid pKa of α -COOH pKa of α -NH 3 + pKa of side chain pI Lysine (Lys) 2.18 8.95 10.53 9.74 Aspartic acid (Asp) 2.10 9.82 3.86 2.98 Histidine (His) 1.77 9.18 6.10 7.64 Glutamic acid (Glu) 2.10 9.47 4.07 3.08 Alanine (Ala) 2.35 9.87 - 6.11 Leucine (Leu) 2.33 9.74 - 6.04 Tyrosine (Tyr) 2.20 9.11 10.07 5.63 Glutamine (Gln) 2.17 9.13 - 5.65 1. Consult above Table for pKa-values of the ionizable groups. (a) Write the form of lysine most prevalent at pH 1.0 and then show its reaction with the following. (i) 1 mol NaOH (ii) 2 mol NaOH (iii) 3 mol NaOH (b) Write the form of aspartic acid most prevalent at pH 1.0 and then show its reaction with the following. (i) 1 mol NaOH (ii) 2 mol NaOH (iii) 3 mol NaOH (c) For asp and glu the isoelectric point occurs at a pH where the net charge on the two carboxyl groups is -1 and balances the charge of +1 on the α -amino group. Calculate the pI of aspartic acid and glutamic acids and compare
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This note was uploaded on 09/07/2009 for the course CHEM 2183 taught by Professor Jonnjardarson during the Spring '09 term at Cornell University (Engineering School).

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Problem_Set_11 - Chem 358 - Spring 2009 Problem Set 11...

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