Analysis of Bitter Orange Petitgrain Essential Oil by Combined Gas Chromatography-Mass Spectrometry

Candida catenulata CBS 1904, the previous type strain of C. ravautii, was selected as the best strain for the production of threo-O_s-isocitric acid from water-insoluble carbon sources, non-carbohydrates. The addition of surfactants, lipophilic polyoxyethylene nonyl phenyl ethers, was essential for the acid production, because the cell surface of the strain was less lipophilic. «-Alkanes, ranging from C_n to C_l4, gave the acid in high yields. The acid was produced in ajar fermentor in an about 90% yield on a weight basis as to «-tetradecane supplied. The acid was easily recovered, as crystals of its monopotassium salt, from the concentrated culture broth filtrate.     

Identification of n-Decane Oxidation Products in Corynebacterium Cultures by Combined Gas Chromatography-Mass Spectrometry

The gas chromatography-mass spectrometry technique was employed to characterize n-decane oxidation products of Corynebacterium strains 7E1C and 269 (SNAM Progetti collection) after 73 h of incubation at 35 C. Corynebacterium 7E1C accumulated consistent amounts of esters of long chain acids with long chain alcohols, mainly decyldecanoate as well as products with mono- and diterminal carboxylic functions. Corynebacterium 269 yielded 1-decanol and 1-10 decanediol as principal oxidation products.     

Identification of Fatty Acids and Aliphatic Hydrocarbons in Sarcina lutea by Gas Chromatography and Combined Gas Chromatography-Mass Spectrometry

The composition and nature of the fatty acids and hydrocarbons of Sarcina lutea were elucidated by gas chromatography and by combined gas chromatography-mass spectrometry. The distribution of fatty acids found in S. lutea showed two families of pairs, or dyads, of saturated monocarboxylic acids (C12-C18) with and without methyl branching. These pairs of fatty acids showed a pattern of iso and anteiso structures for C13, C15, and C17, and iso and normal structures for C12, C14, and C16. Only the C18 showed unsaturation. The distribution of hydrocarbons in the range C22-C29 showed two families of tetrads of unsaturated aliphatic hydrocarbons all showing methyl branching. Each tetrad was composed of four isomers identified as two iso olefins and two anteiso olefins. The only difference between the tetrads pertaining to different families was found in the relative gas chromatographic retention times of the last two components of each group.     

Role of Abscisic Acid in Seed Dormancy

Seed dormancy is an adaptive trait that improves survival of the next generation by optimizing the distribution of germination over time. The agricultural and forest industries rely on seeds that exhibit high rates of germination and vigorous, synchronous growth after germination; hence dormancy is sometimes considered an undesirable trait. The forest industry encounters problems with the pronounced dormancy of some conifer seeds, a feature that can lead to non-uniform germination and poor seedling vigor. In cereal crops, an optimum balance is most sought after; some dormancy at harvest is favored because it prevents germination of the physiologically mature grain in the head prior to harvest (that is, preharvest sprouting), a phenomenon that leads to considerable damage to grain quality and is especially prominent in cool moist environments. The sesquiterpene abscisic acid (ABA) regulates key events during seed formation, such as the deposition of storage reserves, prevention of precocious germination, acquisition of desiccation tolerance, and induction of primary dormancy. Its regulatory role is achieved in part by cross-talk with other hormones and their associated signaling networks, via mechanisms that are largely unknown. Quantitative genetics and functional genomics approaches will contribute to the elucidation of genes and proteins that control seed dormancy and germination, including components of the ABA signal transduction pathway. Dynamic changes in ABA biosynthesis and catabolism elicit hormone-signaling changes that affect downstream gene expression and thereby regulate critical checkpoints at the transitions from dormancy to germination and from germination to growth. Some of the recent developments in these areas are discussed.     

Assay of Malondialdehyde in Biological Fluids by Gas Chromatography-Mass Spectrometry

Malondialdehyde (MDA) is assayed in femtomole quantities in biological samples by gas chromatography-mass spectrometry (GC-MS). The MDA trapped in protein as a Schiff base is released by H₂SO₄, the protein precipitated using Na₂WO₄, and the MDA derivatized with pentafluorophenylhydrazine to form the stable adduct, N-pentafluorophenylpyrazole. Negative chemical ionization (NCI) capability allows the sensitive detection of this MDA adduct in biological samples at a level of 5 nM on-column. A stable-isotope-labeled MDA, [²H₂]MDA, was used as an internal standard for quantitation. MDA recovery from plasma was 76%. This assay provides two forms of confirmation of the analyte, retention time and mass ion, thus minimizing error due to interfering compounds. The commonly used thiobarbituric acid assay for MDA overestimates the MDA levels by over 10-fold, possibly resulting from cross-reactivity with other aldehydes and artifactual oxidation due to 100°C temperature conditions. In our assay, all steps were performed at room temperature thereby suppressing artifactual oxidation of the sample. We have successfully applied this assay to biological samples including plasma, tissue homogenates, and sperm.     

Seed Dormancy in Acer: The Role of Testa-imposed and Embryo Dormancy in Acer velutinum

The embryo dormancy shown in freshly harvested samples of Acervelutinum seeds is weakly established and very short-lived.Loss of this embryo dormancy occurred during post-harvest fruitstorage at either 5 or 17 C. In contrast, the dormancy of intactfruits and seeds was overcome only during storage at the lowertemperature. Removal of the cotyledons from embryos of freshlyharvested fruits allowed more rapid germination of the embryonicaxes, indicating that the cotyledons exert an inhibitory effect,although the axes still retained a measure of innate dormancy.The inhibitory effect of the cotyledons became less marked withincreasing duration of fruit storage, this loss of inhibitoryeffect occurring at both storage temperatures. Applied ABA stronglysuppressed germinative capacity in intact embryos and isolatedembryonic axes from freshly harvested fruits, but when ABA wasapplied to embryos of fruits that had been stored for variousperiods at 5 or 17 C, the inhibitory effect was first weakenedand then lost with increased storage. Although dormancy in the seeds of A. velutinum may be describedas intermediate between testa-imposed dormancy and true dormancy,it is perhaps more properly included in the former category. Acer velutinum Boiss. var. vanvolxemii, abscisic acid, embryo dormancy, germination, seed storage, testa-imposed dormancy, tissue sensitivity     

Demonstration of Conjugated Dopamine in Monkey CSF by Gas Chromatography-Mass Spectrometry

Abstract: A method for measuring unconjugated and conjugated dopamine in body tissues and fluids is described. Conjugated dopamine was hydrolyzed in acid to unconjugated dopamine, separated from the sample matrix by alumina chromatography, and assayed by gas chromatography-mass spectrometry. Conjugated dopamine was detected in greater concentrations than unconjugated dopamine in CSF taken from lateral ventricle or thecal sac of the Rhesus monkey. Haloperidol administration did not increase the levels of conjugated dopamine in lumbar CSF.     

Distribution of Putrescine in Rat Brain Measured by Gas Chromatography-Mass Spectrometry

We measured putrescine levels in minute sites of single rat brains using a sensitive, specific assay involving gas chromatography-mass spectrometry. The putrescine level was measured in 20 sites of single rat brains: three sites in the cerebral cortex, six sites in the hypothalamus, three sites in the basal ganglia, three sites in the thalamus, three sites in the limbic system, and two sites in the cerebellum. The level of putrescine was very high in the hypothalamus, high in the basal ganglia and limbic system, and low in the thalamus, cerebellum, and two of the three sites in the cerebral cortex. The highest levels were in the anterior hypothalamic area and the lateral hypothalamic area, and the lowest levels were in the vermis and the lobe of the cerebellum.     

Identification and Determination of Tele-Methylhistamine in Cerebrospinal Fluid by Gas Chromatography-Mass Spectrometry

Abstract: The presence of tele-methylhistamine in human cerebrospinal fluid has been established. The concentration was determined with the use of deuterated tele-methylhistamine. The preparation of the deuterated standard is described. The concentration range in samples from neuropsychiatric patients was 0.1-2.5 ng/ml. The structure of the pentafluoropropionyl derivative used for gas chromatography was studied with the aid of proton nuclear magnetic resonance spectroscopy.     

Identification of Gibberellins in Norway Spruce (Picea abies [L.] Karst.) by Combined Gas Chromatography-Mass Spectrometry

Gibberellins A₁ (GA₁), A₃ and A₉ were identified from extracts of shoots of 6-month old Norway spruce (Picea abies) seedlings by the use of sequential reverse and normal phase high performance liquid chromatography (HPLC), bioassay, radioimmunoassay (RIA) and combined gas chromatography-mass spectrometry (GC-MS). The bioassay and RIA were used after fractionation by HPLC to detect the GA-containing fractions, which were then examined by GC-MS. The GAs identified are considered to be endogenous.     

The Role of the Oxygen Permeability of the Seed Coat in the Dormancy of Seed of Xanthium pennsylvanicum Wallr

A method for direct identification and quantitative measurementsof mixed or pure gases diffusing through seed coats was devisedto test the hypothesis that the dormancy of Xanthium pennsylvanicumseeds is caused by oxygen-impermeable seed coats. The diffusionof oxygen through seed coats of X. pennsylvanicum was shownto obey Fick's first law. Oxygen diffused through the lowerand upper seed coats at the same rate. Imbibed lower and upperseeds showed essentially equal oxygen uptake rates before radicleemergence. This uptake was lower than the rate at which oxygencan diffuse into the seed. Therefore upper seeds are not dormantbecause of seed coat restriction of oxygen diffusion. The relationshipsof oxygen with other factors involved in seed dormancy are discussed.     

缬草油化学成份GC/MS分析研究

利用GC、GC/MS对缬草油的化学成分进行分析 ,共鉴定出 6 5种化合物 ,其中有 2 6种物质为相关文献中首次报道。所介绍的分析方法可用于生产中的质量监控和常规分析 ,分析结果可为配方、产品开发和调香等提供指导     

木荷花挥发性成分的GC-MS分析

采用无水乙醚超声萃取得到新鲜木荷(Schima superba)花浸膏提取物,顶空固相微萃取富集挥发性成分,气相色谱-质谱联用仪分析,归一化法计算各组分的相对含量.鉴定出挥发性化合物中的51个成分,约占相对总含量的99%;挥发性成分中含氧化合物的含量超过93%,其中主要的化合物及其相对含量为酮代异佛尔酮(26.33%)、氧化芳樟醇(19.53%)、环氧芳樟醇(8.80%)、3,7-二甲基-2,6-辛二烯-1-醇(8.23%)、白藜芦素(7.89%)、4-羟基3,5,5-三甲基-2-环己烯-1-酮(6.54%)、2,6,6-三甲基-1,4-环己二酮(4.06%)、苯乙醇(2.17%)、2-甲基-2-壬烯-1-醇(2.04%)等.     

Tanned or Burned: The Role of Fire in Shaping Physical Seed Dormancy

Plant species with physical seed dormancy are common in mediterranean fire-prone ecosystems. Because fire breaks seed dormancy and enhances the recruitment of many species, this trait might be considered adaptive in fire-prone environments. However, to what extent the temperature thresholds that break physical seed dormancy have been shaped by fire (i.e., for post-fire recruitment) or by summer temperatures in the bare soil (i.e., for recruitment in fire-independent gaps) remains unknown. Our hypothesis is that the temperature thresholds that break physical seed dormancy have been shaped by fire and thus we predict higher dormancy lost in response to fire than in response to summer temperatures. We tested this hypothesis in six woody species with physical seed dormancy occurring in fire-prone areas across the Mediterranean Basin. Seeds from different populations of each species were subject to heat treatments simulating fire (i.e., a single high temperature peak of 100°C, 120°C or 150°C for 5 minutes) and heat treatments simulating summer (i.e., temperature fluctuations; 30 daily cycles of 3 hours at 31°C, 4 hours at 43°C, 3 hours at 33°C and 14 hours at 18°C). Fire treatments broke dormancy and stimulated germination in all populations of all species. In contrast, summer treatments had no effect over the seed dormancy for most species and only enhanced the germination in Ulex parviflorus, although less than the fire treatments. Our results suggest that in Mediterranean species with physical dormancy, the temperature thresholds necessary to trigger seed germination are better explained as a response to fire than as a response to summer temperatures. The high level of dormancy release by the heat produced by fire might enforce most recruitment to be capitalized into a single post-fire pulse when the most favorable conditions occur. This supports the important role of fire in shaping seed traits.     

Nitrate Reduction in a Groundwater Microcosm Determined by 15N Gas Chromatography-Mass Spectrometry

Aerobic and anaerobic groundwater continuous-flow microcosms were designed to study nitrate reduction by the indigenous bacteria in intact saturated soil cores from a sandy aquifer with a concentration of 3.8 mg of NO₃⁻-N liter⁻¹. Traces of ¹⁵NO₃⁻ were added to filter-sterilized groundwater by using a Darcy flux of 4 cm day⁻¹. Both assimilatory and dissimilatory reduction rates were estimated from analyses of ¹⁵N₂, ¹⁵N₂O, ¹⁵NH₄⁺, and ¹⁵N-labeled protein amino acids by capillary gas chromatography-mass spectrometry. N₂ and N₂O were separated on a megabore fused-silica column and quantified by electron impact-selected ion monitoring. NO₃⁻ and NH₄⁺ were analyzed as pentafluorobenzoyl amides by multiple-ion monitoring and protein amino acids as their N-heptafluorobutyryl isobutyl ester derivatives by negative ion-chemical ionization. The numbers of bacteria and their [methyl-³H]thymidine incorporation rates were simultaneously measured. Nitrate was completely reduced in the microcosms at a rate of about 250 ng g⁻¹ day⁻¹. Of this nitrate, 80 to 90% was converted by aerobic denitrification to N₂, whereas only 35% was denitrified in the anaerobic microcosm, where more than 50% of NO₃⁻ was reduced to NH₄⁺. Assimilatory reduction was recorded only in the aerobic microcosm, where N appeared in alanine in the cells. The nitrate reduction rates estimated for the aquifer material were low in comparison with rates in eutrophic lakes and coastal sediments but sufficiently high to remove nitrate from an uncontaminated aquifer of the kind examined in less than 1 month.     

黄芪多糖结构及其单糖组成的气相色谱-质谱研究

目的:研究不同样品黄芪多糖的结构和单糖组成差异。方法:采用闪式提取、乙醇沉淀法从黄芪根部提取多种多糖化合物,脱除蛋白、凝胶层析后的多糖化合物经水解、乙酰化后利用气相色谱-质谱法分析黄芪水溶性多糖中单糖组成、结构及其比例,将同样的方法应用到8个不同产地或不同级别的黄芪样品中。结果:黄芪多糖所含单糖种类主要有L-鼠李糖、L-阿拉伯糖、D-木糖、L-木糖、D-核糖、L-核糖、D-半乳糖,D-葡萄糖,D-甘露糖,且不同黄芪样品所含黄芪多糖里含有的单糖种类及含量有较大差别。结论:该研究可为黄芪品种甄别及黄芪多糖品质分析提供参考。     

Assay of 2-Hydroxyputrescine in Various Regions of Rat Brain by Gas Chromatography-Mass Spectrometry

2-Hydroxyputrescine in seven regions of single rat brains was measured with a sensitive, specific assay by gas chromatography-mass spectrometry. The regions were the cerebral cortex, cerebellum, medulla oblongata, hypothalamus, striatum, hippocampus, and midbrain. The level of 2-hydroxyputrescine was very high in the cerebral cortex and cerebellum, high in the medulla oblongata, hypothalamus, and hippocampus, and low in the striatum and midbrain. The level of 2-hydroxyputrescine in the cerebellum was significantly higher than in the striatum and midbrain.     

黄芪多糖结构及其单糖组成的气相色谱-质谱研究

目的:研究不同样品黄芪多糖的结构和单糖组成差异.方法:采用闪式提取、乙醇沉淀法从黄芪根部提取多种多糖化合物,脱除蛋白、凝胶层析后的多糖化合物经水解、乙酰化后利用气相色谱-质谱法分析黄芪水溶性多糖中单糖组成、结构及其比例,将同样的方法应用到8个不同产地或不同级别的黄芪样品中.结果:黄芪多糖所含单糖种类主要有L-鼠李糖、L-阿拉伯糖、D-木糖、L-木糖、D-核糖、L-核糖、D-半乳糖,D-葡萄糖,D-甘露糖,且不同黄芪样品所含黄芪多糖里含有的单糖种类及含量有较大差别.结论:该研究可为黄芪品种甄别及黄芪多糖品质分析提供参考.     

气相色谱质谱法测定食品包装材料中24种邻苯二甲酸酯(英文)

目的:建立同时检测食品包装材料中24种邻苯二甲酸酯类化合物的气相色谱质谱法(GC-MS)分析方法。方法:用正己烷提取包装材料,GC-MS选择离子监测模式(SIM)测定,运用气质联用仪测定24种邻苯二甲酸酯类物质。结果:24种邻苯二甲酸酯类物质的线性范围为0.05 mg/L~10 mg/L,除了邻苯二甲酸二异壬酯(DINP)和邻苯二甲酸二异癸酯(DIDP)为0.5 mg/L~10 mg/L,相关系数(r2)除DINP、DIDP外均大于0.99,方法的检出限(信噪比为3)为0.002 mg/kg~0.05 mg/kg,在食品包装材料基质中3个加标水平的平均回收率为85.2%~108%,相对标准偏差(RSD,n=6)为5.9%~10.2%。结论:该方法快速、灵敏、准确可靠,适用于食品包装材料中邻苯二甲酸酯类化合物的分析检测。