Molecular Biology of the Cell by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter by by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morg

ACIDIC SIDE CHAINS
aspartic acid
(Asp, or D)
glutamic acid
(Glu, or E)
H
H O
O
O O – C
N C C
N C C
H CH 2
H CH 2
C
CH 2
O O –
UNCHARGED POLAR SIDE CHAINS
asparagine
(Asn, or N)
glutamine
(Gln, or Q)
H O
H O
N C C
N C C
H CH 2
H CH 2
C
CH 2
O NH 2 C
O NH 2
Although the amide N is not charged at
neutral pH, it is polar.
NONPOLAR SIDE CHAINS
alanine
(Ala, or A)
N
H
H
C
CH 3
H
C
O
C
leucine
(Leu, or L)
N
O
C
H CH 2
CH
CH 3 CH 3
proline
(Pro, or P)
N
N
H
H
C
CH 2
(actually an CH 2
imino acid)
methionine
(Met, or M)
H
C
CH 2
CH 2
O
C
CH 2
O
C
113
H CH 2
valine
(Val, or V)
H O
N C C
H CH
CH 3 CH 3
H O
N C C
H CH
CH 3 CH 2
CH 3
phenylalanine
(Phe, or F)
H O
N C C
H CH 2
tryptophan
(Trp, or W)
H O
N C C
serine
(Ser, or S)
threonine
(Thr, or T)
tyrosine
(Tyr, or Y)
S CH 3
N
H
H
O
H
O
H
O
glycine
cysteine
N
C
C
N
C
C
N
C
C
(Gly, or G)
(Cys, or C)
H CH 2
H
CH
CH 3
H CH 2
H
O
H
O
OH
OH
N
C
C
N
C
C
H
H
H
CH 2
OH
SH
The –OH group is polar.
Disulfide bonds can form between two cysteine side chains
in proteins.
CH 2 S S CH 2