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Results for “13c labeling”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2003

[13C]-Specific labeling of 8-2' linked (-)-cis-blechnic, (-)-trans-blechnic and (-)-brainic acids in the fern Blechnum spicant

In vivo administration experiments using stable (13C) and radio (14C) labeled precursors established that the optically active 8-2' linked lignans, (-)-cis-blechnic, (-)-trans-blechnic and (-)-trans-brainic acids, were directly derived from L-phenylalanine, cinnamate, and p-coumarate but not either from tyrosine or acetate. The radiochemical time course data suggest that the initial coupling product is (-)-cis-blechnic acid, which is then apparently converted into both (-)-trans-blechnic and (-)-trans-brainic acids in vivo. These findings provide additional evidence for vascular plant proteins engendering distinct but specific phenolic radical-radical coupling modes, i.e., for full control over phenylpropanoid coupling in vivo, whether stereoselective or regiospecific.

NASA Discipline Plant Biology↗

NASA NTRS1999

Lipid synthesis under hydrothermal conditions by Fischer-Tropsch-type reactions

Ever since their discovery in the late 1970's, mid-ocean-ridge hydrothermal systems have received a great deal of attention as a possible site for the origin of life on Earth (and environments analogous to mid-ocean-ridge hydrothermal systems are postulated to have been sites where life could have originated or Mars and elsewhere as well). Because no modern-day terrestrial hydrothermal systems are free from the influence of organic compounds derived from biologic processes, laboratory experiments provide the best opportunity for confirmation of the potential for organic synthesis in hydrothermal systems. Here we report on the formation of lipid compounds during Fischer-Tropsch-type synthesis from aqueous solutions of formic acid or oxalic acid. Optimum synthesis occurs in stainless steel vessels by heating at 175 degrees C for 2-3 days and produces lipid compounds ranging from C2 to > C35 which consist of n-alkanols, n-alkanoic acids, n-alkenes, n-alkanes and alkanones. The precursor carbon sources used are either formic acid or oxalic acid, which disproportionate to H2, CO2 and probably CO. Both carbon sources yield the same lipid classes with essentially the same ranges of compounds. The synthesis reactions were confirmed by using 13C labeled precursor acids.

Non-NASA Center↗

NASA NTRS2017

IR Spectra and Properties of Solid Acetone, an Interstellar and Cometary Molecule

Mid-infrared spectra of amorphous and crystalline acetone are presented along with measurements of the refractive index and density for both forms of the compound. Infrared band strengths are reported for the first time for amorphous and crystalline acetone, along with IR optical constants. Vapor pressures and a sublimation enthalpy for crystalline acetone also are reported. Positions of 13C-labeled acetone are measured. Band strengths are compared to gas-phase values and to the results of a density-functional calculation. A 73% error in previous work is identified and corrected.

IR spectroscopy, band strengths, astrochemistry, a↗

NASA NTRS1994

Evidence for only minor contributions from bacteria to sedimentary organic carbon

Because their molecular signatures are often prominent in extracts of sediments, bacteria are thought to be important contributors to petroleum source beds. It has been shown recently, however, that abundances of biomarkers do not always reflect relative contributions to sedimentary organic carbon (Corg). The contribution of photosynthetic green sulphur bacteria to sediments can be assessed effectively because the diagenetic products of distinctive carotenoids from these organisms occur widely and their biomass is isotopically labelled, being enriched in 13C. We show here that, although sediments and oils from the Western Canada and Williston basins contain prominent biomarkers of photosynthetic bacteria, the absence of 13C enrichment in the total Corg requires that the bacterial contribution is in fact minimal. Although the importance of bacterial reworking of sedimentary debris cannot be doubted, we argue that our findings, when considered in conjunction with those from other settings, suggest that bacterial biomass may commonly represent only a minor component of total Corg in carbonaceous rocks.

NASA Discipline Exobiology↗

NASA NTRS1995

Hydroxycinnamic acid-derived polymers constitute the polyaromatic domain of suberin

Suberin is an abundant, complex, intractable, plant cell wall polymeric network that forms both protective and wound-healing layers. Its function is, therefore, critical to the survival of all vascular plants. Its chemical structure and biosynthesis are poorly defined, although it is known to consist of both aromatic and aliphatic domains. While the composition of the aliphatic component has been fairly well characterized, that of the phenolic component has not. Using a combination of specific carbon-13 labeling techniques, and in situ solid state 13C NMR spectroscopic analysis, we now provide the first direct evidence for the nature of the phenolic domain of suberin and report here that it is almost exclusively comprised of a covalently linked, hydroxycinnamic acid-derived polymeric matrix.

NASA Discipline Plant Biology↗