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Double-bond Position (double-bond + position)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Acute toxicity of fatty acids to the freshwater green alga Selenastrum capricornutum

ENVIRONMENTAL TOXICOLOGY, Issue 5 2003
Yasushi Kamaya
Abstract The acute toxicity of fatty acids (C14 to C18) commonly found in wood was determined by the standard algal growth inhibition test using the freshwater green alga Selenastrum capricornutum. Toxicity, quantified as IC50 values, varied depending on the number of total carbons and double bonds. Of the tested acids, oleic (cis -9-octadecenoic) acid showed the highest toxicity (72-h IC50 = 0.47 mg/L) to the alga, and triolein, a triglyceride of oleic acid, showed no apparent toxicity. Further examination of a series of C18:1 acids with a double bond at the 6, 11, or 12 position revealed that both double-bond position and cis or trans configuration affected toxicity. The 72-h IC50 data for these fatty acids and related compounds seemed to correlate well with the melting point (mp), showing two separate linear relationships: at mp < 35°C toxicity increased with increasing melting point, and at mp > 40°C toxicity decreased with melting point. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 289,294, 2003. [source]

Sterol-induced upregulation of phosphatidylcholine synthesis in cultured fibroblasts is affected by the double-bond position in the sterol tetracyclic ring structure

FEBS JOURNAL, Issue 21 2000
Petra Leppimäki
We have examined how a specific enrichment of cultured fibroblasts with various sterols (cholesterol, lathosterol, 7-dehydrocholesterol, allocholesterol and dihydrocholesterol) regulate synthesis de novo of phosphatidylcholine, cholesterol and cholesteryl (or steryl) esters in human skin fibroblasts. When human skin fibroblasts were incubated for 1 h with 130 µm cholesterol/CyD complexes, the mass of cellular free cholesterol increased by 100 nmol·mg,1 protein (from 90 nmol·mg,1 to 190 nmol·mg,1 protein). A similar exposure of cells to different sterol/CyD complexes increased the cell sterol content between 38 and 181 nmol sterol per mg cell protein. In cholesterol-enriched cells, the rate of phosphatidylcholine synthesis was doubled compared to control cells, irrespective of the type of precursor used ([3H]choline, [3H]palmitic acid, or [14C]glycerol). Enrichment of fibroblasts with 7-dehydrocholesterol, allocholesterol, or dihydrocholesterol also upregulated phosphatidylcholine synthesis, whereas cells enriched with lathosterol failed to upregulate their phosphatidylcholine synthesis. The activity of membrane-bound CTP:phosphocholine cytidylyltransferase, the rate-limiting enzyme, was increased by 47 ± 4% in cholesterol-enriched cells whereas its activity was unchanged in lathosterol-enriched cells. Sterol enrichment with all tested sterols (including lathosterol) down-regulated acetate-incorporation into cholesterol, and upregulated sterol esterification in the sterol-enriched fibroblasts. Using 31P-NMR to measure the lamellar-to-hexagonal (L,,HII) phase transition in multilamellar lipid dispersions, lathosterol-containing membranes underwent their transition at significantly higher temperatures compared to membranes containing any of the other sterols. In a system with 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphoethanolamine and either cholesterol or lathosterol (70 : 30 mol/mol), differential scanning calorimetry also revealed that the L,,HII -transition occurred at a higher temperature with lathosterol compared to either cholesterol, allocholesterol, or dihydrocholesterol. These findings together suggest that there may exist a correlation between the propensity of a sterol to stabilize the L,,HII -transition and its capacity to upregulate the activity of CTP:phosphocholine cytidylyltransferase in cells. [source]

A method for the identification of the double-bond position of isomeric linear tetradecenols and related compounds based on mass spectra of dimethyl disulfide derivatives

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2002
Gu Yuan
A simple method is presented for calculation of the double-bond position in linear tetradecenols based on mass spectral data of dimethyl disulfide derivatives. In this approach, the m/z ratios of the molecular ion and of one (or both) of the two most abundant fragment ions were utilized to calculate the double-bond position, without the requirement to identify both fragment ions resulting from carbon-carbon cleavage across what was originally the double bond. The approach was tested with mass spectra of dimethyl disulfide derivatives of 12 isomeric tetradecenols, and the double-bond position in each isomer was successfully identified by this method. The method was shown to work also for the corresponding acetates. Copyright © 2001 John Wiley & Sons, Ltd. [source]