Question

draw the predominate form

1. Draw the predominate form that the following tripeptide will assume at pHTA Trp-Asp-Arg Suppose the tripeptide above was placed in solutions buffered to the pH values given below the net charge of the tripeptide at those pH values? what would be a. pH = 10.0 b. pH = 3.0 2. Suggest a denaturant that might specifically disrupt (i.e., denature) the attractive force or covalent linkage that can form between each of the following amino acid residues. Assume the protein is at pH 7.4 a) Leucine and Isoleucine b) Arginine and glutamic acid c) Cysteine and cysteine

Answer 1

if pH < pKa then all the ionizable NH2 will be protonated and will exist as NH3+

if pH > pKa then all the ionizable COOH will be deprotonated and will exist as COO-

pKa of a-NH2 of Trp = 9.39

pKa of Asp side chain (COOH) = 3.86

pKa of alpha COOH of Arg : 2.17

Right-click to copy or save image H N NH NH2 H2N

AT pH 10

HN NH H2N NH2 R W pH 10 nePcharge - OH HN NH "H2N NH2 pH 3 net charge +1 R W D

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