Problem_Set__11_solution - Chem 3580 - Spring 2009 Problem...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chem 3580 - Spring 2009 Problem Set 11 - Solutions Additional problems on amino acids and peptides Amino acid pKa of -COOH pKa of -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) At pH 1.0 the amino acid will be fully protonated as shown below. H 3 N COOH NH 3 2 mol NaOH H 2 N COO NH 3 H 3 N COOH NH 3 3 mol NaOH H 2 N COO NH 2 H 3 N NH 3 1 mol NaOH H 3 N COO NH 3 (i) (ii) (iii) COOH (b) At pH 1.0 the amino acid will be fully protonated as shown below. H 3 N COOH COOH H 3 N COO COOH (ii) H 3 N COOH COOH H 3 N COO COO H 3 N COOH COOH H 2 N COO COO (iii) 1 mol NaOH 2 mol NaOH 3 mol NaOH (i) (c) Answer: Asp 2.98 Glu 3.085 (d) (i) pH 6.8 is more acidic than pI 7.64. So His has a net + charge: negative electrode (ii) pH 6.8 is more acidic than pI 9.74. Lys has a net + charge: negative electrode (iii) pH 4.0 is more basic than pI 3.08. Glu has a net charge: positive electrode. Note that the pH 4.0 is almost (iii) pH 4....
View Full Document

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).

Page1 / 4

Problem_Set__11_solution - Chem 3580 - Spring 2009 Problem...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online