page_title: Archaeol
section_title: Chemistry
hierarchical_section_title: Archaeol / Chemistry
caption_attribution_description: English: Sesterterpanyl archaeol
context_page_description: Archaeol is one of the main core membrane lipids of archaea, one of the three domains of life. One of the key features that distinguishes archaea from bacteria and eukarya is their membrane lipids, where archaeol plays an important role. Because of this, archaeol is also broadly used as a biomarker for ancient archaea, especially methanogens, activity.
  Archaeol is generally composed by linking two phytanyl chains to the sn-2 and sn-3 positions of a glycerol molecule. The highly branched side chains are speculated to account for the very low permeability of archaeol-based membrane, which may be one of the key adaptations of archaea to extreme environments.
context_section_description: Archaeol is a diether lipid commonly found in archaea. Standard archaeol is 2,3-di-O-phytanyl-sn-glycerol, with two phytanyl chains binding to the position of sn-2 and sn-3 of glycerol by ether bonds. The 2,3-sn-glycerol structure and ether bond linkage are two key differences of archaea lipids from those of bacteria and eukarya that use 1,2-sn-glycerol, and mostly, ester bonds. Natural archaeol has 3R, 7R, 11R configurations for the three chiral centers in the isoprenoid chains. There are four structural variations, contributing to the complexity of the membrane lipids in function and properties. The two phytanyl chains can form a 36-member ring to yield macrocyclic archaeol. Hydroxylated archaeol has phytanyl chains hydroxylated at the first tertiary carbon atom, while sesterterpanyl archaeol have the phytanyl side chains with C25 sesterterpanyl chains, substituting at C2 of glycerol or at both carbons. Unsaturated archaeol, with the same carbon skeleton as standard archaeol but one or multiple double bonds in the phytanyl side chains is also discovered.
  Two archaeol molecules can undergo head-to-head linkage to form caldarchaeol (one typical glycerol dialkyl glycerol tetraether, GDGT), one of the most common tetraether lipid in archaea.
caption: Sesterterpanyl archaeol, formed by substituting the phytanyl (C20) chains in the standard archaeol by sesterterpanyl (C25) chains.
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