REACTIVE OXYGEN SPECIES - Oxidation of Amino Acids, Peptides, and Proteins: Kinetics and Mechanism - page 160

(a) peptide fluorescence

sealed ghosts

(b) GITWK

from 03 treated cytochrome c

500

30

400

300

20

GWVIH (loop)

200

10

WMEAAR (tail)

100

0 0

0.0 0.5 1.0 1.5 2.0 -5 0 5 10 15 20 25

µ mole ozone

minute ozone

BSA Vs Ozone (d) HSA Vs Ozone

(c)

100 50

FWGK (peptide)

80 40

60 30

40 20

AWAVAR (peptide)

20 10

AWSVAR (peptide)

0 0

0 1 2 3 4 0 1 2 3 4

µ mole ozone

µ mole ozone

Figure 4.17. (a) Band 3 fluorescent peptides, (b) peptide gITWK from O 3 -treated
cytochrome c , (c) fluorescent peptides from O 3 -treated BSA, and (d) fluorescent pep-
tides from O 3 -treated HSA (redrawn from Mudd et al. [232]).

cm), Tyr (ε 277 nm = 1500/M/cm), and Phe (ε 254 nm = 200/M/cm) [258]. His had a
maximum at 210 nm and was buried by the amide n → π* transition. Disulfide
(S-S) was another bond in proteins, which absorbed at 250 nm (ε 277nm = 300/M/
cm). In the O 3 -treated samples, the intensity of the peak at 275 nm decreased
with a shift to shorter wavelengths and finally its elimination with an increase
in the O 3 dosage. The intensity of the peaks at 222 nm remained similar, which
indicated the attack on the amide group of the protein chain by O 3 was not
significant.
In the ozonation of invertase and pectinase samples (Fig. 4.18a,b), a new
peak at 327 nm appeared, which accounted for the formation of quinines and
a ketone group attached to the benzene ring from the oxidation of aromatic
amino acids. In the case of pectinase, an additional peak at 240 nm appeared
from the oxidation of cys and the formation of S-S bonds. Both papain and