1. Structural formulas of 20 amino acids common in proteins
_
COO
+ Non-polar groups
Glycine H3N CH H
Gly
G
_
COO
+
Alanine H3N CH CH3
Ala
A
_
COO CH3
+
Valine H3N CH CH CH3
Val
V
_
COO CH3
+
Leucine H3N CH CH2 CH CH3
Leu
L
_
COO CH3
+
Isoleucine H3N CH CH CH2 CH3
Ile
I
_
COO
CH2
Proline CH
CH2
Pro
HN
P CH2
_
COO
+
Groups with S
Cysteine H3N CH CH2 SH
Cys
C
_
COO
+
Methionine H3N CH CH2 CH2 S CH3
Met
M
_
COO
+
Polar OH groups
Serine H3N CH CH2 OH
Ser
S
_
COO OH
+
Threonine H3N CH CH CH3
Thr
T
By Israel Hanukoglu, Ph.D. http://www.science.co.il/Biomedical/Molecules/Amino-Acids/

2. _
COO O
+
Polar amide groups
Asparagine H3N CH CH2 C NH2
Asn
N
_
COO O
+
Glutamine H3N CH CH2 CH2 C NH2
Gln
Q
_
COO O
Charged (−), acidic
+ +
Aspartic acid H3N CH CH2 C O H
Asp
D
_
COO O
+ +
Glutamic acid H3N CH CH2 CH2 C O H
Glu
E
_
COO
NH
Charged (+), basic
+
Histidine H3N CH CH2
His N
H
_
COO
+ +
Lysine H3N CH CH2 CH2 CH2 CH2 NH3
Lys
K
_ +
COO NH2
+
Arginine H3N CH CH2 CH2 CH2 NH C NH2
Arg
R
_
COO
+ Aromatic groups
Phenylalanine H3N CH CH2
Phe
F
_
COO
+
Tyrosine H3N CH CH2 OH
Tyr
Y
_
COO
+
Tryptophan H3N CH CH2
Trp NH
W
By Israel Hanukoglu, Ph.D. http://www.science.co.il/Biomedical/Molecules/Amino-Acids/