Diagenesis at the molecular level

Epimerization (see Section 2.1.3) converts the single, biologically conferred configuration at a stereogenic centre into an equilibrium mixture of the two possible 

It was noted in Section 3.3.1 that phytoplankton and their remains upon death sink only very slowly, allowing ample opportunity for predation by zooplankton 

Isomerization at a stereogenic centre in a biomarker is an example of a reversible reaction in which reactant and product have similar energies. 

Fatty acid distributions can be affected by microbial oxidation in sediments, so care must be exercised when certain components are used as source indicators. For example, (3-hydroxy fatty acids are produced from (3-oxidation of saturated fatty acids. In addition, C0-oxidation of saturated fatty acids to CO-hydroxy acids and of CO-hydroxy acids to a,CO-diacids is performed by yeasts (unicellular fungi, mainly belonging to the as-comycetes) and bacteria. Consequently, while the long-chain ( C22) CO-hydroxy acids are reliable indicators of higher plant sources, the short-chain components 

The main inputs of chlorophyll-derived compounds to sediments under oxidizing conditions are usually pyrophaeophorbides, due to the activity of zooplank- 

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