Non-α-Toeopherols in the Unicellular Blue-Green Alga <i>Gloeocapsa</i>

Newton, Russell P.; Walton, Terence J.; Moyse, Christopher D.

doi:10.1042/bst0051486

Cited by 9 publications

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“…However, in the molecular structure of tocopherol, there is a hydroxy group at C-6 position, and the existence 6-methyl isomer in methylated chromans in geological samples can preclude the possibility that tocopherol may be the biological precursor of methylayted chromans in the geological samples. In addition, tocopherols have been widely dis-tributed in various organisms such as higher plants, bacteria and algae [16,17] , but in geological samples, their distributions are very limited, mainly in immature to mar- ginal-mature source rocks and crude oils from hypersaline and brackish environment. What is the reason to control this geological distribution for this kind of specific compounds?…”

Section: Distribuions and Compositions Of Methylated Chromans In The mentioning

confidence: 99%

The relationship between methylated chromans and maturity of organic matter in the source rocks from Jianghan hypersaline basin

Bao

Zhu

2009

Sci. China Ser. D-Earth Sci.

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Citation: Bao J P, Zhu C S, Ma A L. The relationship between methylated chromans and maturity of organic matter in the source rocks from Jianghan Hypersaline The distribution, the relative composition, and their variation of methylated chromans (MTTC) with maturation of organic matter in the source rocks from Mingjia 1 well, Jianghan hypersaline basin, have been analyzed and studied. There is a close relationship between the distribution of methylatd chromans and paleosalinity of depositional environment. In the Eq 1 -Eq 3 source rocks deposited under hypersaline environment with lower Pr/Ph ratio, higher gammacerane index and abundant organic sulfur-containing compounds, methyl MTTC and dimethyl MTTC are main components, but in the Eq 4 source rocks deposited non-hypersaline environment with relatively higher Pr/Ph ratio, lower gammacerane index and organic sulfur-containing compounds, trimethyl MTTC is a major compound in methylate chromans. Obviously, the distributions and the compositions of methylated chromans in the source rocks are in harmony with biomarker indicators indicating the paleaosalinity and redox of depositional environment. The relationship between the ratio of 5,8-dimethyl MTTC to 7,8-dimethyl MTTC (dimethyl MTTC ratio) and the maturity of organic matter in the source rocks from Mingjia 1 well has been discussed. The results show that dimethyl MTTC ratio increased with the burial depth and the maturation of organic matter in the source rocks, especially in immature level. It is noteworthy that this ratio is very susceptible to small variation in the maturity of organic matter in the source rocks when vitrinite reflectance R o is less than 0.65%. It may imply that this ratio is a good and susceptible aromatic maturity indicator for the relative maturity of organic matter in immature source rocks. methylated chromans, dimethyl MTTC ratio, source rock, Jianghan hypersaline basin, depositional environment, maturity of organic matter Because of some unusual biomarker assemblages, much more attention have be paid to the geochemistry of the source rocks and the crude oils from hypersaline environment [1,2] . For example, there is an even carbon preference in normal alkane series and abnormally lower Pr/Ph ratio in isoprenoid series [3,4] . In addition, in biomarker assemblages, higher gammacerane index, high homohopane index and abundant organic sulfur compounds are other important characteristics [5][6][7] for the source rocks and crude oils from hypersaline environment. It may be related to specific flora and organic matter input under hypersaline environment with specific conditions of water chemistry.Methylated chromans with an isoprenoid side chain (2-methyl-2-(4,8,12-trimethyltridecyl), MTTCs), including 6-methyl, 8-methyl, 5,8-dimethyl, 7,8-dimethyl and 5,7,8-trimethyl-2-methyl-(4,4,12-trimethyltridecyl) chromans, are a kind of important compounds and

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Section: Distribuions and Compositions Of Methylated Chromans In The mentioning

confidence: 99%

The relationship between methylated chromans and maturity of organic matter in the source rocks from Jianghan hypersaline basin

Bao

Zhu

2009

Sci. China Ser. D-Earth Sci.

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“…However, N,, fixation was less sensitive to Oj stress in mutants of Azospirillum brasilense that overproduced carotenoids, even though the optimum concentration of O.^ for N,^ fixation remained unchanged (Hartmann & Hurek, 1988). Tocopherols have been reported in the diazotrophic cyanobacterium Gloeothece (Newton, Walton & Moyse, 1977;Mullins et al, 1986). In this organism, 8-tocopherol was relatively abundant even though only 2"o of its fatty acid was polyunsaturated.…”

Section: Notesmentioning

confidence: 99%

“…In this organism, 8-tocopherol was relatively abundant even though only 2"o of its fatty acid was polyunsaturated. This implies a role for ^-tocopherol other than in prevention of membrane lipid peroxidation, and Newton et al (1977) suggested that such a role could be protection of nitrogenase from oxidative damage, (c) 'Conformational' protection. When cultures of Azotobacter are exposed briefly to high concentrations of O2, N,2 fixation is inhibited ('switch-off').…”

Section: Notesmentioning

confidence: 99%

Reconciling the incompatible: N₂ fixation And O₂

1992

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summary N2 fixation is an extremely O2‐sensitive process. N2‐fixing bacteria (diazotrophys) have therefore evolved a variety of strategies by which they maintain an active nitrogenase in the presence of atmospheric O2 and, in some cases, of O2 generated photosynthetically. In this review, the effects of O2 on nitrogenase activity and synthesis are described, as are the mechanisms by which diazotrophs limit O2damage to nitrogenase. These mechanisms are classified as behavioural strategies, physical barriers or physiological and biochemical strategies. Individual diazotrophs frequently empoly a combination of these. In addition, the particular problems faced by the O2‐evolving cyanobacteria are discussed.

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“…However, N,, fixation was less sensitive to Oj stress in mutants of Azospirillum brasilense that overproduced carotenoids, even though the optimum concentration of O.^ for N,^ fixation remained unchanged (Hartmann & Hurek, 1988). Tocopherols have been reported in the diazotrophic cyanobacterium Gloeothece (Newton, Walton & Moyse, 1977;Mullins et al, 1986). In this organism, 8tocopherol was relatively abundant even though only 2"o of its fatty acid was polyunsaturated.…”

Section: Notesmentioning

confidence: 93%

“…In this organism, 8tocopherol was relatively abundant even though only 2"o of its fatty acid was polyunsaturated. This implies a role for ^-tocopherol other than in prevention of membrane lipid peroxidation, and Newton et al (1977) suggested that such a role could be protection of nitrogenase from oxidative damage, (c) 'Conformational' protection. When cultures of Azotobacter are exposed briefly to high concentrations of O2, N,2 fixation is inhibited ('switch-off').…”

Section: Notesmentioning

confidence: 99%

Untitled

1992

New Phytologist

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N2 fixation is an extremely Oj-sensitive process. N,-fixing bacteria (diazotrophs) have therefore evolved a variety of strategies by which they maintain an active nitrogenase in the presence of atmospheric Oj and, in some cases, of Og generated photosynthetically. In this review, the effects of O.^ on nitrogenase activity and synthesis are described, as are the mechanisms by which diazotrophs limit O,, damage to nitrogenase. These mechanisms are classified as behavioural strategies, physical barriers or physiological and biochemical strategies. Individual diazotrophs frequently employ a combination of these. In addition, the particular problems faced by the O.^evolving cyanobacteria are discussed.

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Non-α-Toeopherols in the Unicellular Blue-Green Alga Gloeocapsa

Cited by 9 publications

References 0 publications

The relationship between methylated chromans and maturity of organic matter in the source rocks from Jianghan hypersaline basin

The relationship between methylated chromans and maturity of organic matter in the source rocks from Jianghan hypersaline basin

Reconciling the incompatible: N₂ fixation And O₂

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Non-α-Toeopherols in the Unicellular Blue-Green Alga Gloeocapsa

Cited by 9 publications

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The relationship between methylated chromans and maturity of organic matter in the source rocks from Jianghan hypersaline basin

The relationship between methylated chromans and maturity of organic matter in the source rocks from Jianghan hypersaline basin

Reconciling the incompatible: N2 fixation And O2

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Reconciling the incompatible: N₂ fixation And O₂