Lipid biomarkers structures

Lipid biomarkers as indicators of microbial activity and community structure... 

Phospholipid fatty acid analysis (PLFA) is based on the determination of signature lipid biomarkers from the cell membranes and walls of microorganisms. Phospholipids are an essential part of intact cell membranes, and information from the lipid analysis provides quantitative insight into three important attributes of microbial communities viable biomass, community structure, and nutritional status. Phospholipid fatty acid prohles have been used to show the response of the microbial community to phosphorus availability (Keinanen et ah, 2002). Signature lipid biomarker analysis may not detect every species of microorganism in an environmental sample accurately, because many species have similar PLFA patterns. 

In the present chapter, we first provide some general information concerning the chemistry of waxes and lipids currently encountered in various items from our cultural heritage and we detail the main protocols based on direct mass spectrometry that have been developed so far. We then discuss the mass spectra obtained by EI-MS on a range of reference substances and materials sampled from museum and archaeological artefacts. We then focus on the recent possibilities supplied by electrospray ionisation for the elucidation of the structure of biomarkers of beeswax and animal fats. 

Hence, direct mass spectrometry techniques, either using El or ESI, appear to be powerful and innovative analytical tools for elucidating the structure of the main biomarkers present in a wide range of waxes and lipids that may be preserved in archaeological objects and in museum works of art. In most cases, they have nevertheless to be cautiously exploited in combination with other complementary analytical techniques. 

All organisms synthesize carbohydrates, lipids, proteins, and polynucleotides, although the details of their molecular structures can be somewhat species specific. These basic classes of macromolecules have changed little over geologic time. The secondary metabolites are more species specific and have also changed little over geologic time. Many are resistant to degradation, and those provide excellent biomarkers that have been preserved in ancient marine sediments and petroleum deposits. 

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