29. Amino Acids

Draw the form of aspartate that predominates at the following pH values:

d. pH=11.0

c. Which amino acid has the greatest amount of negative charge at pH = 6.20?

Draw the predominant form for glutamate in a solution with the following pH:

a. 0

Draw the structure of the predominant form of

(e) a mixture of alanine, lysine, and aspartic acid at (i) pH 6;

Alanine has pK_a values of 2.34 and 9.69. Therefore, alanine exists predominately as a zwitterion in an aqueous solution with pH >____ and pH <____.

The pH–activity profile for glucose-6-phosphate isomerase indicates the participation of a group with a pK_a = 6.7 as a basic catalyst and a group with a pK_a = 9.3 as an acid catalyst. Draw the pH–activity profile and identify the amino acids that participate in the catalysis.

Draw the structure of the predominant form of

(a) isoleucine at pH 11.

Identify the location and type of charge on the hexapeptide Lys-Ser-Asp-Cys-His-Tyr at each of the following pH values:

d. pH=12

Draw the form of aspartate that predominates at the following pH values: c. pH=6.0