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Parchment, a biologically based material obtained from the processed hides of animals such as cattle and sheep, has been used for millennia as a writing medium. Although numerous studies have concentrated on the structure and degradation of collagen within parchment, little attention has been paid to noncollagenous components, such as lipids. In this study, we present the results of biochemical and structural analyses of historical and newly manufactured parchment to examine the potential role that lipid plays in parchment stability. The lipid fraction extracted from the parchments displayed different fatty acid compositions between historical and reference materials. Gas chromatography, small-angle X-ray scattering, and solid-state NMR were used to identify and investigate the lipid fraction from parchment samples and to study its contribution to collagen structure and degradation. We hypothesize that the origin of this lipid fraction is either intrinsic, attributable to incomplete fat removal in the manufacturing process, or extrinsic, attributable to microbiological attack on the proteinaceous component of parchments. Furthermore, we consider that the possible formation of protein-lipid complexes in parchment over the course of oxidative degradation may be mediated by reactive oxygen species formed by lipid peroxidation.

The possibility of separating lipid materials on the basis of the number, type, and position of the unsaturated centers they contain, by virtue of the complexing of these unsaturated bonds with silver ions, provides a relatively recent but now very important addition to the range of separatory methods available to lipid chemists and biochemists. In this review, the nature of the complexing of silver ions with olefins is considered briefly and the history of the development of separation methods based on argentation is traced. Some practical considerations of argentation chromatography are discussed and separations of fatty acids and aldehydes, substituted fatty acids, neutral lipids, polar lipids, and sterols and other terpenoid compounds, by argentation methods alone and in conjunction with other separation techniques, are then reviewed. Some conclusions are finally presented as to the present and potential utility of argentation methods in studies of the occurrence, metabolism, and function of lipids.