Geology Reference
In-Depth Information
Dictyonema peltatum
+
P2
10
+
+
+
+
15
B3
20
+
+
+
+
+
+
Gly
+
N
+
Retention time
Fig. 9.2 Partial ion chromatogram showing the pyrolysis-GC/MS analysis of Dictyonema peltatum
revealing the absence of any protein moieties and the presence of a dominant aliphatic component.
+: n -alkanes; −: n -alkenes; B3 : trimethyl benzene; P2 : dimethyl phenol/ethyl phenol; Gly : glycerin;
N : naphthalene
for hydroxyproline, is characteristic of collagen (Stankiewicz et al. 1997a ).
Pyrimidine is also derived from collagen, although it cannot be ascribed to any
particular amino acid. The m/z 85 + 83 (Fig. 9.1a ) mass chromatogram revealed a
series of n -alkanes and n -alkenes. However, analysis of Rhabdopleura periderm
after lipid extraction did not reveal the presence of these n -alkanes and n -alkenes
(fi gure not shown), indicating that they were derived from a soluble, probably lipid,
component.
Thermochemolysis of Rhabdopleura (Fig. 9.1b ) revealed a distribution of fatty
acyl moieties ranging in carbon number from C 7 to C 18 . C 16 and C 18 saturated and
unsaturated components were the most abundant (see Fig. 9.1b : m/z 74 + 87).
Homologues greater than C 10 showed an even over odd predominance.
Samples of the graptolites Paleodictyota anastomotica , Dictyonema peltatum
and Diplograptus sp. were analysed after solvent extraction. No moieties diagnostic
of collagen were detected (Fig. 9.2 ). The graptolites comprised a largely aliphatic
polymer with n -alkyl components in the pyrolysate extending at least from C 9 to
C 21 ; C 10 to C 15 alkane/alkene homologues were the most abundant (Fig. 9.2 ,
Table 9.1 ). A very similar distribution of chain lengths was observed in Monograptus
and Amphigraptus (Briggs et al. 1995 , Table 9.1 ). The aromatic component detected
in all these consisted of benzene derivatives, phenols and naphthalene. Some glyc-
erin was detected in the analysis of Dictyonema peltatum (Fig. 9.2 ), presumably as
a result of contamination from the storage medium which could not be completely
removed during extraction (no glycerin was detected in the samples obtained
directly from rock).
Fatty acyl moieties released by thermochemolysis of the same graptolite samples
(Fig. 9.3 ) ranged from C 7 to C 18 with an even-over-odd predominance (especially for
those >C 10 ). The most abundant of these were C 16 and C 18 fatty acyl moieties, both
saturated and unsaturated. These fatty acyl moieties were dominant when compared
to the alkane/alkene homologues (see mass chromatogram m/z 74 + 87 + 85 + 83).
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