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Alkenone

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Alken sune methyl da ethyl n-ketons masu tsawo waɗanda wasu nau'ikan phytoplankton na ajin Prymnesiophyceae suka samar.[1] Alkenones yawanci suna dauke da tsakanin 35 da 41 carbon atoms kuma tare da tsakanin biyu zuwa hudu biyu biyu bindings.[2] Musamman ga biolipids, alkenones suna da sarari na ƙungiyoyin methylene guda biyar tsakanin haɗin biyu, waɗanda ke da Tsarin E na yau da kullun. Ayyukan halittu na alkenones ya kasance a cikin muhawara kodayake mai yiwuwa ne cewa su ne ajiyar lipids.[3][4] An fara bayyana alkenones a cikin ruwan teku da aka dawo da su daga Walvis Ridge sannan jim kadan bayan haka a cikin al'adun coccolithophore na ruwa Gephyrocapsa huxleyi. [5][6] Abubuwan da aka fi sani da alkenones sun kasance a lokacin Aptian shekaru miliyan 120 da suka gabata.[7] Ana amfani da su a cikin ilimin kimiyyar halittu a matsayin wakili don zafin jiki na teku da ya gabata.

Tsarin sunadarai na 37:3 alkenone, (8E,15E,22E) -heptatriaconta-8,15,22-trien-2-one, C37H68O

Dabbobi masU samar da alK suna amsawa ga canje-canje a cikin mahallinsu - gami da canje-canje na zafin jiki na ruwa - ta hanyar canza daidaitattun dangi na alkenones daban-daban da suke samarwa. A yanayin zafi mafi girma ana samar da alkenones masu cike da daidaito. Wannan yana nufin cewa za'a iya amfani da matakin dangi na rashin cikawa na alkenones don kimanta zafin jiki na ruwa wanda kwayoyin da ke samar da alkenone suka girma.[1] Matsayin dangi na rashin cikawa kamar yadda aka fara bayyanawa (UK37) ya haɗa da tetra unsaturated C37 alkenone:

U = (C37:2 - C37:4) / (C37: 2 + C37:3 + C37:4) [8]  

Koyaya, ƙididdigar ƙarancin ƙarancin ƙarfi (U '37), gabaɗaya mafi amfani a cikin saitunan ruwa, ya dogara ne akan di- da tri- unsaturated C37 alkenones kuma an bayyana shi kamar haka:

U = C37:2/ (C37:2 + C37:3) [9]  

Za'a iya amfani da BU '37 don kimanta yawan zafin jiki na teku bisa ga dangantakar da aka ƙayyade daga daidaitawar saman. Tsarin da aka fi amfani dashi shine na Müller et al., 1998:

U = 0.033T [°C] + 0.044 [10]

Müller et al. (1998) daidaitawa bai dace da duk mahalli ba kuma, musamman, ana buƙatar daidaitawa daban-daban don manyan latitudes da saitunan lacustrine.

Manazarta

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  1. ↑ Marlowe, I.T.; Green, J.C.; Neal, A.C.; Brassell, S.C.; Eglinton, G.; Course, P.A. (1984). "Long chain (n-C37–C39) alkenones in the Prymnesiophyceae. Distribution of alkenones and other lipids and their taxonomic significance". British Phycological Journal. 19 (3): 203–216. doi:10.1080/00071618400650221.
  2. ↑ Rontani, Jean‐François; Prahl, Fredrick G.; Volkman, John K. (2006). "RE‐EXAMINATION OF THE DOUBLE BOND POSITIONS IN ALKENONES AND DERIVATIVES: BIOSYNTHETIC IMPLICATIONS". Journal of Phycology. 42 (4): 800–813. doi:10.1111/j.1529-8817.2006.00251.x. S2CID 84316762.
  3. ↑ Epstein, B.L.; d'Hondt, S.; Hargraves, P.E. (2001). "The possible metabolic role of C37 alkenones in Emiliania huxleyi". Organic Geochemistry. 32 (6): 867–875. Bibcode:2001OrGeo..32..867E. doi:10.1016/S0146-6380(01)00026-2.
  4. ↑ Eltgroth, Matthew L.; Watwood, Robin L.; Wolfe, Gordon V. (2005). "PRODUCTION AND CELLULAR LOCALIZATION OF NEUTRAL LONG‐CHAIN LIPIDS IN THE HAPTOPHYTE Algae ISOCHRYSIS GALBANA AND EMILIANIA HUXLEYI". Journal of Phycology. 41 (5): 1000–1009. doi:10.1111/j.1529-8817.2005.00128.x. S2CID 22092773.
  5. ↑ De Leeuw, J.W.; v.d. Meer, F.W.; Rijpstra, W.I.C.; Schenck, P.A. (1980). "On the occurrence and structural identification of long chain unsaturated ketones and hydrocarbons in sediments". Physics and Chemistry of the Earth. 12: 211–217. Bibcode:1980PCE....12..211D. doi:10.1016/0079-1946(79)90105-8.
  6. ↑ Volkman, J.K.; Eglinton, G.; Corner, E.D.S.; Sargent, J.R. (1980). "Novel unsaturated straight-chain C37C39 methyl and ethyl ketones in marine sediments and a coccolithophore Emiliania huxleyi". Physics and Chemistry of the Earth. 12: 219–227. Bibcode:1980PCE....12..219V. doi:10.1016/0079-1946(79)90106-X.
  7. ↑ Brassell, Simon C.; Dumitrescu, Mirela (2004). "Recognition of alkenones in a lower Aptian porcellanite from the west-central Pacific". Organic Geochemistry. 35 (2): 181–188. doi:10.1016/j.orggeochem.2003.09.003.
  8. ↑ Brassell, S. C.; Eglinton, G.; Marlowe, I. T.; Pflaumann, U.; Sarnthein, M. (1986). "Molecular stratigraphy: A new tool for climatic assessment". Nature. 320 (6058): 129–133. Bibcode:1986Natur.320..129B. doi:10.1038/320129a0. S2CID 4366905.
  9. ↑ Prahl, F. G.; Wakeham, S. G. (1987). "Calibration of unsaturation patterns in long-chain ketone compositions for palaeotemperature assessment". Nature. 330 (6146): 367–369. Bibcode:1987Natur.330..367P. doi:10.1038/330367a0.
  10. ↑ Müller, Peter J.; Kirst, Georg; Ruhland, Götz; von Storch, Isabel; Rosell-Melé, Antoni (1998). "Calibration of the alkenone paleotemperature index U37K′ based on core-tops from the eastern South Atlantic and the global ocean (60°N-60°S)". Geochimica et Cosmochimica Acta. 62 (10): 1757–1772. doi:10.1016/S0016-7037(98)00097-0.

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