A pentapeptide has the sequence of H2N-Glu–His–Leu-Arg-Gly-COOH. a) What is the net charge of the peptide at pH 3, 8, and 11? (Use pka values for side chains and terminal amino and carboxyl groups in the table provided.) peptide. b) Estimate the pl for this
A pentapeptide has the sequence of H2N-Glu–His–Leu-Arg-Gly-COOH. a) What is the net charge of the peptide at pH 3, 8, and 11? (Use pka values for side chains and terminal amino and carboxyl groups in the table provided.) peptide. b) Estimate the pl for this
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Transcribed Image Text:1. A pentapeptide has the sequence of H2N-Glu-His-Leu-Arg-Gly-COOH. a) What is the net
charge of the peptide at pH 3, 8, and 11? (Use pka values for side chains and terminal
amino and carboxyl groups in the table provided.)
peptide.
b) Estimate the pl for this
pK, values
Abbreviation/
symbol
pk,
M, (-COOH) (-NH5) (R group)
pK;
pKR
Hydropathy Occurrence in
index* proteins (%)*
Amino acid
pl
Nonpolar, aliphatic
R groups
Glycine
Alanine
Proline
Valine
2.34
-0.4
Gly G
Ala A
Pro P
75
9.60
5.97
7.2
89
115
2.34
9.69
10.96
6.01
6.48
5.97
1.8
1.6
4.2
3.8
4.5
7.8
5.2
1.99
117
131
Val V
2.32
2.36
9.62
9.60
6.6
9.1
Leucine
Leu L
5.98
Isoleucine
lle I
131
2.36
2.28
9.68
6.02
5.3
Methionine
Met M
149
9.21
5.74
1.9
2.3
Aromatic R groups
Phenylalanine
Tyrosine
Tryptophan
2.8
-1.3
3.9
3.2
Phe F
165
1.83
9.13
9.11
9.39
5.48
2.20
Tyr Y
Trp W
181
10.07
5.66
204
2.38
5.89
-0.9
1.4
Polar, uncharged
R groups
Serine
Ser S
105
2.21
6.8
9.15
9.62
5.68
5.87
5.07
5.41
5.65
-0.8
Threonine
Thr T
119
2.11
-0.7
5.9
1.9
Cysteine
Asparagine
Glutamine
Cys C
Asn N
121
132
146
1.96
2.02
2.17
10.28
8.18
2.5
4.3
4.2
8.80
-3.5
Gin Q
9.13
-3.5
Positively charged
R groups
Lysine
Histidine
Arginine
Lys K
His H
Arg R
9.74
-3.9
-3.2
146
2.18
8.95
10.53
5.9
155
1.82
9.17
6.00
7.59
2.3
174
2.17
9.04
12.48
10.76
-4.5
5.1
Negatively charged
R groups
Aspartate
Glutamate
Asp D
Glu E
133
147
2.77
3.22
1.88
5.3
9.60
9.67
3.65
4.25
-3.5
2.19
-3.5
6.3
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