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Fig. 6.4
An expanded view
of the
13
C NMR spectra
of (
a
) model compound
chitin, (
b
) fresh shrimp
and scorpion cuticle and
(
c
) shrimp and scorpion
cuticle decayed for 44 weeks.
Grey line
corresponds to
shrimp cuticle and
black line
to scorpion cuticle.
Ch
denotes peaks related to
chitin. The
open circle
(O)
highlights the presence of
olefi nic carbon. The protein
component is evident at ~40
and 115-140 ppm (Note the
signifi cant aliphatic carbon
peak (30 ppm) in shrimp
cuticle after 44 weeks decay
as compared to fresh shrimp,
and fresh and decayed
scorpion cuticle)
a
Chitin
Ch
Ch
Ch
Ch
Ch
Ch
Ch
Ch
b
Undecayed shrimp
and scorpion
Ch
Ch
Ch
Ch
Ch
Ch
O
O
Aliphatic
carbon
c
44 week decayed shrimp
and scorpion
Ch
Ch
Ch
Ch
Ch
Ch
Ch
O
O
160
140
120
100
80
60
40
20
0
ppm
aliphatic carbon chain numbers up to
n
-C
30
were the dominant pyrolysis products,
and phenols were barely detected (Stankiewicz et al.
2000
). Subsequent experi-
ments (Gupta et al.
2006c
) involving maturation of a mixture of pure C
16
and C
18
fatty acids (similar to those obtained from extraction and hydrolysis of the lipid
component of the cuticle) produced a distribution of
n
-alkane/alkene homologues
similar to that in the matured untreated cuticles. In striking contrast, maturation of
cuticle that had fi rst been extracted and saponifi ed (i.e., was devoid of labile ali-
phatic compounds) yielded no aliphatic component but only moieties related to
matured chitin and protein. These results provided the initial experimental evidence
that lipids present in the extractable and hydrolysable fraction of the arthropod cuti-
cle are critical for the formation of the aliphatic component. Similar experiments
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