Bovine thyroid glands are known to contain a complex array of gangliosides. One of the predominant gangliosides was isolated and analyzed by gas-liquid chromatography and mass spectrometry. The carbohydrate composition was fucose, N-acetylneuraminic acid, galactose, N-acetylgalactosamine, and glucose in molar ratios of 1:1:2:1:1. The structure of the ganglioside was identified as: 相似文献
In this study, we examined the influence of UV-B radiation (280–320 nm) on ABA accumulation in 14-day-old Arabidopsis thaliana (L.) Heynh plants of wild type (WT), ethylene receptor mutant (etr1-1), and mutant with a constitutively active ethylene signal transduction pathway (ctr1-1). ABA content in nonirradiated WT plants was twice higher than in each mutant. UV-B irradiation caused dose-dependent ABA accumulation in WT plants. In the etr1-1 mutant, the amount of accumulated ABA was significantly less. In the ctr1-1 mutant, ABA content didn’t increase after UV-B irradiation. These data suggest that start of stress-induced ABA formation requires the adjustable ethylene signal pathway. In the ctr1-1 mutant, a constitutively active (nonadjustable) ethylene signal pathway blocks stress-induced ABA accumulation. 相似文献
A facile, sensitive and highly specific HPLC method for assaying 1-(2-chloroethyl)-3-sarcosinamide-1-nitrosourea (SarCNU) in plasma has been developed. The drug was efficiently isolated from plasma by extraction with tert.-butyl methyl ether. A structurally related compound with similar physicochemical properties served as the internal standard (I.S.). Following evaporation of the organic solvent, the extract was reconstituted with 0.05 M ammonium acetate buffer, pH 5.0, and loaded onto a 4 μm Nova-Pak C18 column (15 cm×3.9 mm), which was preceded by a 7 μm Brownlee RP-18 precolumn (1.5 cm×3.2 mm). Chromatography was performed at ambient temperature using a mobile phase of methanol-0.1 M ammonium formate buffer, pH 3.7 (25:75, v/v). UV absorbance of the effluent was monitored at 240 nm. A flow-rate of 1.0 ml/min was used for analyzing mouse and dog plasma extracts. Under these conditions, the drug eluted at 4.0 min and was followed by the I.S. at 6.1 min. An automatic switching valve was employed to allow the precolumn to be flushed 1.5 min into the run, without interrupting the flow of the mobile phase to the analytical column, thereby preventing the apparent build-up of extractable, strongly retained, UV-absorbing components present in mouse and dog plasma. Operating in this manner, more than 100 samples could be analyzed during a day using a refrigerated autosampler for overnight injection. The method was readily adapted to the determination of SarCNU in human plasma by simply decreasing the eluent flow-rate to 0.6 ml/min, whereby SarCNU and the I.S. eluted at approximately 5.8 and 9.1 min, respectively. Furthermore, the switching valve was not necessary for the analysis of human plasma samples. With a 50-μl sample volume, the lowest concentration of SarCNU included in the plasma standard curves, 0.10 μg/ml, was quantified with a 7.8% R.S.D. (n=27) over a 2 month period. Plasma standards, with concentrations of 0.26 to 5.1 μg/ml, exhibited R.S.D. values ranging from 1.3 to 4.7%. Thermospray-ionization MS detection was used to definitively establish the specificity of the method. The sensitivity of the assay was shown by application to be more than adequate for characterizing the plasma pharmacokinetics of SarCNU in mice. 相似文献
N-glycan moiety of ascorbic acid oxidase from zucchini (Cucurbita pepo) has been described to be a core-pentasaccharide with a xylose [D'Andrea et al. (1988) Glycoconjugate J 5:151-7]. Ascorbic acid oxidase is sometimes used to characterize antibodies directed against carbohydrate determinants on plant glycoproteins. To prevent misinterpretations of immunological data, the structure of the N-glycan of ascorbic acid oxidase has been reinvestigated. The oligosaccharides were released by almond N-glycosidase and analysed as their pyridylamino derivatives by 2D-HPLC and exoglycosidase digestions. The main structure resembled the typical complex plant N-glycan consisting of a core-pentasaccharide decorated with xylose and 3-linked fucose. The other abundant species lacked the fucose residue. Small amounts of these glycans carried a GlcNAc residue on the 6-arm. Therefore, ascorbic acid oxidase will not only react with antibodies directed against the xylosylated region but also with those binding to N-glycans with 3-linked fucose. 相似文献
Meiotin-1 is a chromatin-associated protein, originally isolated from microsporocytes of Lilium longiflorum, which is found predominantly in cells undergoing meiotic prophase. Chromatin fractionation studies demonstrated that meiotin-1 has an unusual stoichiometry relative to that of histone H1 and the core histones in chromatin fibers. The protein is found less frequently than is histone H1, and appears to be distributed once every 5 to 13 nucleosomes. This distribution may approximate the number of nucleosomes per turn of the chromatin solenoid. A truncated cDNA was identified by immunoscreening of an expression library, and the cDNA was used as a hybridization probe to select a full length cDNA. Variations between the sequence of the predicted polypeptide and sequenced peptides, and variations between the amino acid composition of the protein and the deduced protein indicate that the cDNAs encode minor variants of mature meiotin-1. RNA gel blot hybridization studies reveal that the meiotin-1 mRNA is restricted to anthers in which meiosis is occurring. Computer analysis of the polypeptide deduced from the cDNA indicates that the protein begins with a region highly homologous to the conserved central globular domain of histone H1 molecules. DNA gel blotting experiments demonstrate that homologous sequences exist in the genomes of a fern, a fungus, and both mono-and dicotyledonous plants. Meiotin-1 has been evolutionarily conserved and I propose that it arose from histone H1 to fulfill a role in organizing meiotic chromatin. 相似文献
N,N-Diethyl-m-toluamide (DEET) is frequently used as an insect repellent by military and civilian populations. Because dermal exposure has resulted in several cases of DEET toxicosis, there is a need to rapidly and reliably determine DEET concentrations in biological matrices. An improved method for the analysis of DEET was developed for determining transdermal diffusion of low levels of DEET following application to an in vitro porcine skin flow-through diffusion cell system. The technical improvement involved the use of disk solid-phase extraction (SPE) instead of packed-bed SPE. The disk SPE method required small volumes of preconditioning, wash, and elution solvent (0.5-1 ml) to extract DEET from perfusate samples containing bovine serum albumin (BSA). The limit of quantitation (LOQ) was estimated as 0.08 micro g/ml DEET and recoveries from BSA media samples spiked with DEET ranged from 90.1 to 117% with relative standard deviation (RSD) ranging from 2.0 to 13.1%. This method was used to analyze perfusate samples from skin (n=4) topically exposed to DEET-ethanol formulations. The data from these analyses determined that DEET permeability in porcine skin was 2.55 x 10(-5)+/-0.54 x 10(-5) cm/h. 相似文献