Question

2. Using the reference pk values provided below (assuming that pk values can be applied to ionazable R groups in peptides) a) Draw the complete structure of the peptide IDKSMH that exists at physiological pH 7.4 b) What is the charge of the peptide at pH 7.4? c) What is the charge of the peptide at pH 10? PR, es pkk ) Rougl Amino acid COOH) Nonpolar, aliphatic Rgroups Glycine Alanine Proline Valine 1.99 10.98 Loucine 236 2.35 921 8.13 2.20 2.21 196 Isoleucine Methionine Aromatic R groups Phenylalanine Tyrosine Tryptophan Polar, uncharted R groups Serine Threonine Cysteine Asparagine Glutamine Positively charged Rgroups Lysine Histidine Anne Negatively changed Roups Aspartate Glutamate 10.28 8.80 2.13 2.17 2.18 5.11 2.17 104 1 2.1996

Answer 1

LIDK SMH OH I isoleucine Aspartic arid: o k= lysine w T serine HO- s OM M = H = methonine. Histidine. pH <pta pH y pla protonated deprotonated. A peptide bond is formed blu carboxylic arid and amuno group releasing a molecule of water.

a At pH 7.4 он Mb чком и - - С- - - со Су Сң-см, -су- ск- смс см.) , , , , (см, дом, , С

y charge of peptide at pH 7.4 I do 0 [11-1=0]. () charge of peptide at pH 10 Isoleucine Nhy will be deprotonated be - NH contributing no change lysine and Nu will also be deprotaned – NV₂ and contribute no. charge only contribution group the charge is both Goo Hence from the change 10 at pH Hence - 2