use pK a = 3.2 the a -COOH group, pK BH = 8.0 for the a -NH 2 group, and the fol
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Question
use pKa = 3.2 the a-COOH group, pKBH = 8.0 for the a-NH2 group, and the following values for dissociation constants for side-chain groups.
Amino Acid Dissociation Constant of Side Chain Group
Aspartic Acid 3.9 (pKa of COOH)
Glutamic Acid 4.2 (pKa of COOH)
Histidine 6.0 (pKBH of =N)
Lysine 10.5 (pKBH of NH2)
Using the information above.
For a mixture of the peptides listed below, predict the order in which these peptides would elute from a cation-exchange column using gradient elution from pH 2 (start) to pH 11 (end).
His-Gly-Ala-Glu Lys-Gly-Ala-Glu Asp-Gly-Ala-Glu Lys-Gly-Ala-Val
Explanation / Answer
The elution order for the peptides would be,
Asp-Gly-Ala-Glu elute first
Lys-gly-Ala-Glu elute next
His-Gly-Ala-Glu elute next
Lys-gly-Ala-Val elute at the end
From the cation exchange chromatography
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