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Biphytane

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Biphytane (or bisphytane) is a C40 isoprenoid moiety produced from glycerol dialkyl glycerol tetraethers (GDGT) degradation.[1] Since it is a moiety of GDGT, a common lipid membrane component, biphytane is widely used as a biomarker for archaea.[2] In particular, given its association with sites of active anaerobic oxidation of methane (AOM), it is considered a biomarker of methanotrophic archaea.[3] It has been found in both marine and terrestrial environments.[2][4]

Biphytane
Names
IUPAC name
3,7,11,15,18,22,26,30-Octamethyldotriacontane
Identifiers
Properties
C40H84
Molar mass 565.112 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Chemical structure

Biphytane is formed by isoprene units bound by ether bonds with six isoprene units (or two phytanes) linked together by a head-to-head linkage.[5] It is produced by the chemical cleavage of the ether bonds within GDGT.[1]

Biphytane can be further cyclized to form cyclic biphytanes containing one to three pentacyclic rings. Among these different forms, the acyclic form is typically the most abundant form any environmental sample analyzed.[2]

Biological origin

As with GDGT, biphytane has been detected in the water column, marine sediments, hydrothermally-influenced sediments, cold seep sediments dominated by AOM activity, and limestone.[2] Though it had been primarily studied in aquatic settings, recent studies have also started investigating terrestrial environments, such as peat bogs where the source of biphytane was associated with methanogenic peat archaea.[4] Studies have reported the detection of biphytane in oils as well.

Analogous to sterols in eukaryotic membranes, biphytane plays a similar role in improving the mechanical properties of the archaeal cell membranes.[6] Supporting this, it has been reported that thermophiles increase the degree of cyclization with increasing growth temperatures to further improve the membrane rigidity.[7]

Measurement techniques

Mass spectral fragment ions characteristic of (acyclic) biphytane. Blue lines mark the location of fragmentation and the associated numbers correspond to the resulting ion fragments' m/z values.

Typically, biphytane measurement is done do indirect analysis of GDGT via chemical degradation. When deriving from such ether lipids, the ether bonds are first cleaved using hydrogen iodide (HI), boron trichloride (BCl3), or boron tribromide (BBr3) that produces alkyl halides. Then, the alkyl halides are either reduced to saturated hydrocarbons using HI/NaSCH3 or LiAlD4 or converted to methylthioesthers with NaSCH3. The obtained saturated or derivatized hydrocarbons can subsequently be separated and measured using standard GC-MS procedures.[5]

Alternatively, direct analysis of GDGT can be done with liquid chromatography but, when further structural characterization is required, MS fragments characteristic of biphytane can be obtained via HPLC-MS2.[8]

The diganostic mass spectral fragment ions for biphytane are m/z 197, 259, 267, 323, 383, 393, and 463.[5] The cyclic biphytanes yield different mass spectral fragment ions making the differentiation of the modified forms of biphytanes present in a sample possible.[9]

Application as a biomarker

Biphytane is considered to have a relatively high stability given its detection in high abundance within both recent and ancient sediments and petroleum suggesting its ability to persist thermal maturation.[6] It should be noted that whether biphytane degrades to shorter isoprenoids over time remains unclear.[10]

Biphytane is well established biomarker of archaea since it is found exclusively in archaea.[2] However, when combined with further analyses, it could be used to gain further insight into the analyzed sample. For instance, the abundance ratio of the biphytane (both acyclic and cyclic) to phytane has been used to distinugish between different groups of anaerobic methanotrophic archaea (ANME) from marine sediments given its higher abundance in ANME-1 than -2.[11]

Alternatively, δ13C measurements could be combined to further confirm the origin. Because methanotrophs utilize isotopically light carbon sources, they are characterized by very negative carbon isotope values (i.e. depleted in 13C).[12] For example, by comparing δ13C values of biphytanic diacids and GDGT derived biphytane from the same seep limestones, a study inferred that, despite the chemical similarity of the compounds, they likely were derived from different sources; while the biphytanic diacids were mostly derived from methane oxidizing euryarchea, the biphytanes were from mixed sources.[13]

References

  1. ^ a b Schouten, Stefan; Wakeham, Stuart G; Damsté, Jaap S. Sinninghe (2001-10-01). "Evidence for anaerobic methane oxidation by archaea in euxinic waters of the Black Sea". Organic Geochemistry. 32 (10): 1277–1281. doi:10.1016/S0146-6380(01)00110-3. ISSN 0146-6380.
  2. ^ a b c d e Saito, Hiroyuki; Suzuki, Noriyuki (2010-09-01). "Distribution of acyclic and cyclic biphytanediols in recent marine sediments from IODP Site C0001, Nankai Trough". Organic Geochemistry. Advances in Organic Geochemistry 2009. 41 (9): 1001–1004. doi:10.1016/j.orggeochem.2010.05.007. ISSN 0146-6380.
  3. ^ Schouten, Stefan; Hopmans, Ellen C.; Sinninghe Damsté, Jaap S. (2013-01-01). "The organic geochemistry of glycerol dialkyl glycerol tetraether lipids: A review". Organic Geochemistry. 54: 19–61. doi:10.1016/j.orggeochem.2012.09.006. ISSN 0146-6380.
  4. ^ a b Pancost, Richard D.; van Geel, Bas; Baas, Marianne; Sinninghe Damsté, Jaap S. (2000). <663:cvardo>2.0.co;2 "δ13C values and radiocarbon dates of microbial biomarkers as tracers for carbon recycling in peat deposits". Geology. 28 (7): 663. doi:10.1130/0091-7613(2000)28<663:cvardo>2.0.co;2. ISSN 0091-7613.
  5. ^ a b c Peters, Kenneth E., Clifford C. Walters, and J. Michael Moldowan. The biomarker guide: Volume 2, Biomarkers and isotopes in petroleum systems and earth history. Cambridge University Press, 2007.
  6. ^ a b Chappe, B.; Albrecht, P.; Michaelis, W. (1982-07-02). "Polar Lipids of Archaebacteria in Sediments and Petroleums". Science. 217 (4554): 65–66. doi:10.1126/science.217.4554.65. ISSN 0036-8075.
  7. ^ Damsté, Jaap S.Sinninghe; Schouten, Stefan; Hopmans, Ellen C.; van Duin, Adri C.T.; Geenevasen, Jan A.J. (2002-10). "Crenarchaeol". Journal of Lipid Research. 43 (10): 1641–1651. doi:10.1194/jlr.M200148-JLR200. {{cite journal}}: Check date values in: |date= (help)CS1 maint: unflagged free DOI (link)
  8. ^ Schouten, Stefan; Hopmans, Ellen C.; Sinninghe Damsté, Jaap S. (2013-01-01). "The organic geochemistry of glycerol dialkyl glycerol tetraether lipids: A review". Organic Geochemistry. 54: 19–61. doi:10.1016/j.orggeochem.2012.09.006. ISSN 0146-6380.
  9. ^ Saito, Ryosuke; Kaiho, Kunio; Oba, Masahiro; Tong, Jinnan; Chen, Zhong-Qiang; Tian, Li; Takahashi, Satoshi; Fujibayashi, Megumu (2017-09-01). "Tentative identification of diagenetic products of cyclic biphytanes in sedimentary rocks from the uppermost Permian and Lower Triassic". Organic Geochemistry. 111: 144–153. doi:10.1016/j.orggeochem.2017.04.013. ISSN 0146-6380.
  10. ^ Finkel, Pablo L.; Carrizo, Daniel; Parro, Victor; Sánchez-García, Laura (2023-05). "An Overview of Lipid Biomarkers in Terrestrial Extreme Environments with Relevance for Mars Exploration". Astrobiology. 23 (5): 563–604. doi:10.1089/ast.2022.0083. ISSN 1531-1074. PMC 10150655. PMID 36880883. {{cite journal}}: Check date values in: |date= (help)CS1 maint: PMC format (link)
  11. ^ Blumenberg, Martin; Seifert, Richard; Reitner, Joachim; Pape, Thomas; Michaelis, Walter (2004-07-27). "Membrane lipid patterns typify distinct anaerobic methanotrophic consortia". Proceedings of the National Academy of Sciences. 101 (30): 11111–11116. doi:10.1073/pnas.0401188101. ISSN 0027-8424. PMC 503748. PMID 15258285.{{cite journal}}: CS1 maint: PMC format (link)
  12. ^ Grice, Kliti; Brocks, Jochen J. (2011), Reitner, Joachim; Thiel, Volker (eds.), "Biomarkers (Organic, Compound-Specific Isotopes)", Encyclopedia of Geobiology, Encyclopedia of Earth Sciences Series, Dordrecht: Springer Netherlands, pp. 167–182, doi:10.1007/978-1-4020-9212-1_29, ISBN 978-1-4020-9212-1, retrieved 2023-05-20
  13. ^ Birgel, Daniel; Elvert, Marcus; Han, Xiqiu; Peckmann, Jörn (2008-01). "13C-depleted biphytanic diacids as tracers of past anaerobic oxidation of methane". Organic Geochemistry. 39 (1): 152–156. doi:10.1016/j.orggeochem.2007.08.013. {{cite journal}}: Check date values in: |date= (help)
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