Environmental Engineering Reference
In-Depth Information
+
Positive
Side chain charge at physiological pH 7. 4
-
Negative
Twenty-one amino acids
Primary structure
amino acid sequence
Amino acids with electrically charged side chains
Positive
Negative
Phe
Gly
Asn
Glu
Arginine
(Arg)
R
Histidine
(His)
Lysine
(Lys)
K
Aspartic acid
(Asp)
Glutamic acid
(Glu)
Gln
H
D
E
Ala
pKa 2.16
pKa 2.03
pKa 1. 70
pKa 25
pKa 1. 95
O
O
O
O
O
Arg
Asp
NH
2
NH
2
NH
2
Ty r
Ser
Met
Lys
Val
His
NH
2
NH
2
Pro
Tr p
pKa 9.00
pKa 9.09
pKa 9.16
pKa 9.66
pKa 9.58
Ille
Cys
Leu
O
-
pKa 3.71
O
N
O
NH
NH
-
O
H
2
N
pKa 6.04
+
NH
3
pKa 4.15
+
NH
2
pKa 10.07
pKa 12.10
Alpha helix
Amino acids with polar uncharged side chains
Special cases
Cysteine
(Cys)
C
Serine
(Ser)
S
Threonine
(Thr)
Asparangine
(Asn)
Glutamine
(Gln)
Selenocysteine
(Sec)
Glycine
(Gly)
Proline
(Pro)
T
N
Q
U
G
P
pKa 1. 91
pKa 2.18
pKa 2.13
pKa 2.20
pKa 2.16
pKa 1. 9
pKa 1. 95
pKa 2.34
Beta sheet
O
O
O
O
O
pKa 10.47
O
O
O
pKa 8.76
pKa 8.96
pKa 9.00
pKa 9.05
NH
2
NH
2
NH
2
NH
NH
2
NH
2
NH
2
NH
2
Secondary structure
regular sub-structures
pKa 10.28
pKa 10
pKa 1. 58
HO
SH
SeH
O
OH
pKa 8.14
O
NH
2
Hemoglobin
NH
2
Amino acids with hydrophobic side chain
Alanine
(Ala)
Valine
(Val)
Isoleucine
(Ile)
Leucine
(Leu)
Methionine
(Met)
Phenylalanine
(Phe)
Ty rosine
(Tyr)
Tr yptophan
(Trp)
A
V
I
L
M
F
Y
W
pKa 2.24
pKa 2.38
pKa 2.18
pKa 2.46
pKa 2.32
pKa 2.26
pKa 2.27
O
O
O
pKa 2.33
O
O
O
NH
2
NH
2
NH
2
NH
2
O
NH
2
P13 protein
NH
2
pKa 9.09
pKa 9.04
pKa 9.34
O
pKa 9.90
NH
2
pKa 9.58
pKa 9.60
Te rtiary structure
three-dimensional structure
NH
2
pKa 9.52
pKa 9.71
S
OH
pKa 10.10
Quaternary structure
complex of protein molecules
Figure 6.20
The 21 amino acids found in eukaryotes, grouped according to their side-chains (left). Macromolecular organi-
sation of proteins (right).
