Reconstruction of the past compound-specific N and C isotopic analyses of sedimentary porphyrins
スポンサーリンク
概要
- 論文の詳細を見る
abstractのみPorphyrins are thought to have derived from biomoleculessuch as chlorophylls and heme, among which eoxophylloerythroetioporphyrins(DPEP) and its analogues arestructurally related to chloropigments. These compounds thuspreserve stable isotopic compositions of N and C ofphototrophs of the past environment. We have developedmethods for precise determinations of N and C isotopiccompositions of individual sedimentary porphyrins andmaleimides, which include isolation and purification ofindividual alkylporphyrins and porphyrin acids by dual-stepHPLC preparation (Kashiyama et al., 2007a). We haveanalyzed various alkylporphyrins and porphyrin acids fromorganic-rich Miocene sediments of the paleo-Japan Sea(Onnagawa Formation) as well as Cretaceous black shales(Livello Selli and Livello Bonarelli, Italy) deposited in thewestern Tethys during the Ocean Anoxic Events (OAEs). TheN isotopic composition of DPEP, which should have derivedin chlorophylls in general, ranged from -6.9 to -3.6‰ (n=7) inthe Miocene shale and -6.6 to -3.9‰ (n=5) in the OAE blackshales, indicating that the N2 fixation was a major process forN assimilation hence the dominance of diazotrophiccyanobacteria in primary production in these paleo-oceans.Furthermore, DPEP were relatively enriched in 13C in bothenvironments (-17.9 to -15.6‰ in the Miocene shale and -20.5to -17.9‰ in the OAE black shales), which suggests relativelysmall carbon isotopic fractionation during photosynthesis andsupports significant contribution of cyanobacteria-derivedchloropigments. We also determined isotopic compositions ofsource-specific porphyrins such as 17-nor-DPEP (derivedfrom chlorophyll-c), 8-nor-DPEP (possibly derived fromdivinylchlorophylls; Kashiyama et al., 2007b) as well asDPEP with extended alkyl side chains and their equivalentsamong porphyrin acids (derived from bacteriochlorophyll c, d,and e; analyzed as maleimides). The latter two porphyrins hadvariable and rather unique isotopic compositions compared toDPEP. Such an approach should allow reconstruction ofcommunity structures of phototrophs and associatedbiogeochemical processes associated with the photosynthesisin the past oceans.
論文 | ランダム
- 密教の阿闍梨について : 善無畏説と現状 (平成三年度 天台宗教學大會記念號)
- 徒然草評釈-129-後七日の阿闍梨
- 『成尋阿闍梨母集』の主題--「延久三年正月卅日」への往還
- 三昧と生活規範-2-三昧と阿闍梨
- 通過列車を嘗めるレッスン(その11)