Question

Using the information in the table below, enter the correct pH that should be used to separate the following three amino acids by electrophoresis:

(a) Glu, Lys, and Thr: pH=?

(b) His, Lys, and Arg: pH=?

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pK_a Values for Ionizable Groups of Amino Acids.

Amino Acid	pKa of α-COOH	pKa of α-NH3+	pKa of Side Chain	Isoelectric Point (pI)
Alanine	2.35	9.87	-	6.11
Arginine	2.01	9.04	12.48	10.76
Asparagine	2.02	8.80	-	5.41
Aspartic acid	2.10	9.82	3.86	2.98
Cysteine	2.05	10.25	8.00	5.02
Glutamic acid	2.10	9.47	4.07	3.08
Glutamine	2.17	9.13	-	5.65
Glycine	2.35	9.78	-	6.06
Histidine	1.77	9.18	6.10	7.64
Isoleucine	2.32	9.76	-	6.04
Leucine	2.33	9.74	-	6.04
Lysine	2.18	8.95	10.53	9.74
Methionine	2.28	9.21	-	5.74
Phenylalanine	2.58	9.24	-	5.91
Proline	2.00	10.60	-	6.30
Serine	2.21	9.15	-	5.68
Threonine	2.09	9.10	-	5.60
Tryptophan	2.38	9.39	-	5.88
Tyrosine	2.20	9.11	10.07	5.63
Valine	2.29	9.72	-	6.00