Chemistry Reference
In-Depth Information
Tyrosine
Phenylalanine
OH
OH
X
X
X
X
X
X
CH
2
CH
2
CH
2
CH
2
N
H
N
H
N
H
N
H
R
C
R
R
C
R
R
C
R
R
C
R
O
O
O
O
Tryptophan
Histidine
O
X
NH
NH
NH
NH
X
HN
O
CH
2
CH
2
CH
2
CH
2
N
H
N
H
N
H
N
H
R
C
R
R
C
R
R
C
R
R
C
R
O
O
O
O
2-Oxo-tryptophan
Methionine
Cysteine
OH
OH
CH
3
CH
3
OH
S O
O
S
O
S
O
O
S O
S
CH
2
CH
2
CH
2
CH
2
CH
2
N
H
N
H
N
H
CH
2
CH
2
R
C
R
R
C
R
R
C
R
N
H
N
H
R
C R
O
R
C
R
O
O
O
O
Methionine
sulfoxide
Methionine
sulfone
Cysteine sulfenic
acid
Cysteine
sulfinic acid
Cysteine
sulfonic acid
(cysteic acid)
Figure 1.4.
Structures of the most common amino acid oxidation products. X denotes
either a halogen or a hydroxyl group (adapted from Roeser et al. [112] with the permis-
sion of Springer Americas).
hydroxylated products as well as products of adjacent peptide bond cleavage.
Examples include simultaneous oxidative halogenation and cleavage of
C-terminal peptide bonds of Trp and Tyr. The size of reactants, pH, and redox
potential of either Trp or Tyr determine the selectivity of the cleavage reaction
[113]. HOCl and hypobromous acid (HOBr) form mostly halogenated Trp, Tyr,
and 2-oxo Trp [114-116]. RNS preferentially oxidize Met, Cys, His, Tyr, Phe,
and Trp. The reaction of NO in oxygenated Cys resulted in nitrosation of the
thiol group [117]. RNS are selective for site-directed labeling of peptides and
proteins. For example, the reduction of nitrated Trp or Tyr to their correspond-
ing aromatic amines is a suitable approach for site-directed labeling [118, 119].
Search WWH ::
Custom Search