Question

What would be the charge of the dipeptide L-alanyl-L-alanine at a pH 6, 1, and 12?

What would be the charge of L-alanyl-L glutamic acid at these pH's? Assume the peptide bond is not hydrolyzed under the conditions used.

I have the answer, but I can't see it visually. Please use basic chemistry structures to show this.

Answer 1

Ans. INSTRUCTIONS: Follow the steps-

I. The Charge on a basic group is given by HH equation for basic groups as shown in the table.

II. The sum of positive charges on all basic groups (-NH₂ group at N-ter, side chains of Arg, His and Lys) gives total POSITIVE charge on the peptide.

III. The Charge on an acidic group (Glu, Asp, Cys, Tyr) is given by HH equation as shown in the table.

IV. The sum of negative charges on all acidic groups (-COOH group at C-ter, side chains of Asp, Glu, Cys, Tyr) gives total NEGATIVE charge on the peptide.

V. The sum of TOTAL POSITIVE and TOTAL NEGATIVE charge gives the net charge on the peptide.

VI. Only acidic and basic groups are accounted for charge calculation.

VII. Use of excel or similar programs is preferred to minimize manual errors and complexity of calculation.

#1. L-alanyl-L-alanine

#2. L-alanyl-L glutamic acid