Homework answers / question archive / pK, values Abbreviation/ Amino acid symbo M COOH) NHj) (R group) 75 89 Glycine Alanine Proline Valine Leucine Isoleucine Methionine Lysine Histidine Arginine Serine Threonine Cysteine Asparagine Glutamine Aspartate Glutamate Phenylalanine Tyrosine Tryptopharn Gly G Ala A Pro P Val V Leu L lle I Met M Lys K His H Arg R Ser S 2

pK, values Abbreviation/ Amino acid symbo M COOH) NHj) (R group) 75 89 Glycine Alanine Proline Valine Leucine Isoleucine Methionine Lysine Histidine Arginine Serine Threonine Cysteine Asparagine Glutamine Aspartate Glutamate Phenylalanine Tyrosine Tryptopharn Gly G Ala A Pro P Val V Leu L lle I Met M Lys K His H Arg R Ser S 2

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pK, values Abbreviation/ Amino acid symbo M COOH) NHj) (R group) 75 89 Glycine Alanine Proline Valine Leucine Isoleucine Methionine Lysine Histidine Arginine Serine Threonine Cysteine Asparagine Glutamine Aspartate Glutamate Phenylalanine Tyrosine Tryptopharn Gly G Ala A Pro P Val V Leu L lle I Met M Lys K His H Arg R Ser S 2.34 2.34 1.99 2.32 2.36 2.36 2.28 2.18 1.82 2.17 2.21 2.11 1.96 2.02 2.17 1.88 2.19 1.83 2.20 2.38 9.60 9.69 10.96 9.62 9.60 9.68 9.21 8.95 9.17 9.04 9.15 9.62 10.28 8.80 9.13 9.60 9.67 115 131 131 149 146 155 174 105 119 121 132 146 133 147 165 181 204 10.53 6.00 12.48 Cys C Asn N GIn Q Asp D Glu E Phe F yr Trp W 3.65 4.25 9.11 10.07 9.39
2. (20 points) pKa values and the three-letter abbreviations of the 20 amino acids are shown at the end of this booklet. Calculate the isoelectric (point) pH values (pl) for the following amino acids and tripeptides. Note that the far left amino acids in the tripeptides represent the N-terminals, and those on the far right represent C terminals. You will also assume that peptide bond formation doesn't affect the pKa values of the individual acidic and basic groups. a) Glutamate b) Cysteine c) Arg-Leu-His d) Asp-Lys-Asn