Ba Stankiewicz

Alternative origin of aliphatic polymer in kerogen

The origin of sedimentary organic matter (kerogen) has been attributed to random recombination reactions of biological components in sediments or to selective preservation of decay-resistant macromolecules. Neither hypothesis explains the aliphatic composition of the cuticle of fossil arthropods. Thermal maturation experiments on modern arthropods, involving confined pyrolysis at 250–360 °C, degrade the chitin-protein complex of the cuticle and transform free aliphatic components into a polymeric structure. The results of the application of electron microscopy and spectroscopic methods to modern, thermally matured, and fossil arthropod cuticles indicate that in situ polymerization of free and ester-bound cuticular lipids can lead to kerogen formation. Thus, fossil arthropod fragments can contribute to sedimentary organic matter.

Chemical preservation of plants and insects in natural resins

The morphological preservation of fossils in amber is remarkable, but their chemical composition is largely unknown. The likelihood of DNA preservation in amber has been questioned but, surprisingly, the fate of more decay–resistant macromolecules such as ligno–cellulose in plants or the chitin–protein complex in insect cuticle has not been investigated. Here we report the results of investigations using pyrolysis–gas chromatography/mass spectrometry (py–GC/MS) of the tissues of insects and the plant Hymenaea from ancient and sub–fossil resins (2–20 ka) from Kenya, and from Dominican amber (25–30 Ma). The volatile components of the resin have penetrated even the internal tissues, resulting in the exceptional three–dimensional preservation of amber inclusions. Chitin is preserved in the bee and ligno–cellulose in the Hymenaea leaf from the Kenyan resins. There was no trace, however, of these macromolecules in tissues in Dominican amber. The presence of aliphatic polymer and sulphur–containing moieties in these tissues indicates that they have undergone diagenetic alteration; in view of this, the preservation in Dominican amber of a macromolecule as labile as DNA would be extraordinary.

Assessment of bog-body tissue preservation by Pyrolysis-Gas Chromatography/Mass Spectrometry

Flash pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) was used to assess the quality and mechanism of protein preservation in the tissue of Iron Age bog bodies from Lindow, UK, and south-eastern Drenthe, The Netherlands. Abundant pyrolysis products of the fresh skin tissue, including 2,5-diketopiperazines of Pro-Gly, Pro-Ala, Pro-Val, Pro-Pro and Hyp, were readily assigned to specific amino acid or dipeptide moieties. Comparison of the pyrolysates of the bog-body tissues with that of modern samples revealed qualitative similarities suggesting good preservation of the collagen and non-collagenous proteins in the ancient tissues. Examination of the pyrolysates of samples of fresh calf skin, which had been treated with various vegetable tanning agents, clearly revealed markers of non-hydrolysable tannins including 1,2-benzenediol, 1,3-benzenediol and 1,2,3-benzenetriol, although chromatographic quality inevitably diminished with increasing functionalization of the compounds. Such markers were not detected in the pyrolysates of the bog-body tissues. Instead 4-isopropenylphenol, a characteristic pyrolysis product of Sphagnum moss, was detected in both solvent-extracted and base-treated samples of tissue. The presence of 4-isopropenylphenol in the pyrolysates of the bog-body tissues provides evidence that their preservation involves reactions of amino acids with sphagnum acid, and possibly other agents derived from the peat. The study constitutes the first chemical characterization of the pyrolysis products of modern and ancient collagen.

Comparison of the analytical performance of filament and Curie-point pyrolysis devices

Abstract A wide range (16) of synthetic polymers, biological and organic geochemical samples was chosen to compare the performance of filament and Curie-point pyrolysis devices in combination with gas chromatography/mass spectrometry (py-GC/MS). The pyrolysis results were compared qualitatively, quantitatively and using statistical data visualization methods. Multivariate visualization methods showed a good reproducibility between consecutive runs of the same sample. Statistical analyses of processed py-GC/MS data and qualitative comparison of total ion and mass chromatograms revealed a high degree of comparability between the data obtained from the two pyrolysis devices. This investigation constitutes the first systematic comparison of the two most widely used pyrolysis devices and demonstrates that their results can be confidently cross-referenced providing that all other analytical variables, e.g. sample size, GC column stationary phase, carrier gas, etc. are strictly controlled.