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排序方式: 共有1992条查询结果,搜索用时 15 毫秒
1.
Phytochemical analysis of dried twigs of Marsdenia roylei (family Asclepiadaceae) has resulted in the isolation of a trisaccharide, maryal, and a diglycoside, rolinose. Their structures were determined as O-beta-D-oleandropyranosyl-(1-->4)-O-beta-D-digitoxopyranosyl++ +-(1-->4)-D- cymaral and ethyl O-beta-D-oleandropyranosyl-(1-->4)-O-3-O-methyl-6-deoxy-beta-D- allopyranoside, respectively, by chemical degradation and spectroscopic methods. 相似文献
2.
3.
《Bioscience, biotechnology, and biochemistry》2013,77(6):1002-1003
TTUR 2-2, an alkalophilic Bacillus strain isolated from soil, grew well in media containing cholic acid (CA) at 5% or higher and efficiently converted 7α- and 12α-hydroxyl groups of CA to keto groups, with the conversion rate for both hydroxyl groups reaching 100% by 72 hours of cultivation. The strain also converted a 3α-hydroxyl group to a keto group, but the conversion rate was about 5% at 72 hours. The strain neither affected any other part of the CA molecule, nor oxidized 7β- or 12 β -hydroxyl groups.By NTG mutagenesis, the following mutants were acquired; (1) converting only the 7α- and 12α-hydroxyl groups, (2) converting only the 12α-hydroxyl group, and (3) converting only the 7α-hydroxyl group. These mutants selectively produce 12-ketochenodeoxycholic acid (12KCDCA), 7-ketodeoxycholic acid (7KDOCA), and 7,12-diketolithocholic acid (7,12DKLCA), from CA; and 7-ketolithocholic acid (7KLCA) from cheno-deoxycholic acid (CDCA), respectively, at high yields, close to 100%. 相似文献
4.
《Molecular & cellular proteomics : MCP》2023,22(2):100490
Aspergillus flavus is a common saprophytic and pathogenic fungus, and its secondary metabolic pathways are one of the most highly characterized owing to its aflatoxin (AF) metabolite affecting global economic crops and human health. Different natural environments can cause significant variations in AF synthesis. Succinylation was recently identified as one of the most critical regulatory post-translational modifications affecting metabolic pathways. It is primarily reported in human cells and bacteria with few studies on fungi. Proteomic quantification of lysine succinylation (Ksuc) exploring its potential involvement in secondary metabolism regulation (including AF production) has not been performed under natural conditions in A. flavus. In this study, a quantification method was performed based on tandem mass tag labeling and antibody-based affinity enrichment of succinylated peptides via high accuracy nano-liquid chromatography with tandem mass spectrometry to explore the succinylation mechanism affecting the pathogenicity of naturally isolated A. flavus strains with varying toxin production. Altogether, 1240 Ksuc sites in 768 proteins were identified with 1103 sites in 685 proteins quantified. Comparing succinylated protein levels between high and low AF-producing A. flavus strains, bioinformatics analysis indicated that most succinylated proteins located in the AF biosynthetic pathway were downregulated, which directly affected AF synthesis. Versicolorin B synthase is a key catalytic enzyme for heterochrome B synthesis during AF synthesis. Site-directed mutagenesis and biochemical studies revealed that versicolorin B synthase succinylation is an important regulatory mechanism affecting sclerotia development and AF biosynthesis in A. flavus. In summary, our quantitative study of the lysine succinylome in high/low AF-producing strains revealed the role of Ksuc in regulating AF biosynthesis. We revealed novel insights into the metabolism of AF biosynthesis using naturally isolated A. flavus strains and identified a rich source of metabolism-related enzymes regulated by succinylation. 相似文献
5.
Addition of fruit cell wall extracts from two muskmelon cultivars into liquid media affected mycotoxin production by a strain of Myrothecium roridum pathogenic to muskmelon. Cell wall extracts from a susceptible cultivar (Iroquois) significantly increased toxin production while cell wall extracts from a resistant cultivar (Hales Best) significantly inhibited toxin production. Media containing 0.1 or 1.0 mg ml–1 stimulated toxin production more than media containing 10 or 100 mg ml–1 of cell wall extracts. Previous studies in our laboratory suggest that roridin E may be involved in virulence or pathogenicity of M. roridum; the present study indicates that cell wall polysaccharides as well as other materials present in cell wall preparations from susceptible host tissue provide a better substrate for toxin production than cell wall preparation from resistant host tissue. 相似文献
6.
Jose L. Vega Vicki L. Holmberg Edgar C. Clausen James L. Gaddy 《Archives of microbiology》1988,151(1):65-70
Intrinsic growth and substrate uptake parameters were obtained for Peptostreptococcus productus, strain U-1, using carbon monoxide as the limiting substrate. A modified Monod model with substrate inhibition was used for modeling. In addition, a product yield of 0.25 mol acetate/mol CO and a cell yield of 0.034 g cells/g CO were obtained. While CO was found to be the primary substrate, P. productus is able to produce acetate from CO2 and H2, although this substrate could not sustain growth. Yeast extract was found to also be a growth substrate. A yield of 0.017 g cell/g yeast extract and a product yield of 0.14 g acetate/g yeast extract were obtained. In the presence of acetate, the maximum specific CO uptake rate was increased by 40% compared to the maximum without acetate present. Cell replication was inhibited at acetate concentrations of 30 g/l. Methionine was found to be an essential nutrient for growth and CO uptake by P. productus. A minimum amount of a complex medium such as yeast extract (0.01%) is, however, required. 相似文献
7.
Improved media for normal human muscle satellite cells: Serum-free clonal growth and enhanced growth with low serum 总被引:5,自引:0,他引:5
Richard G. Ham Judy A. St. Clair Cecelia Webster Helen M. Blau 《In vitro cellular & developmental biology. Plant》1988,24(8):833-844
Summary We have developed a serum-free medium for clonal growth of normal human muscle satellite cells (HMSC). It consists of an optimized
nutrient medium MCDB 120, plus a serum-free supplement, designated SF, that contains epidermal growth factor (EGF), insulin,
dexamethasone, bovine serum albumin, and fetuin. Fibroblast growth factor was needed with dialyzed fetal bovine serum (dFBS)
as the only other supplement, but in media containing SF, it was only slightly beneficial, and was omitted from the final
medium without significant loss. Clonal growth of HMSC in MCDB 120 plus SF is as good as with 15% serum and 0.5% chicken embryo
or bovine pituitary extract. However, growth is further improved by use of a doubly-supplemented (DS) medium containing both
SF and 5% dFBS. Clonal growth of HMSC in the DS medium far exceeds that in previous media with any amount of serum, and monolayer
growth is at least equal to that in conventional media with higher levels of serum. Cells grown in these media exhibit little
differentiation, even when grown to high densities. However, they retain the capacity for extensive fusion and synthesis of
increased creatine kinase when transferred to a serum-free differentiation-promoting medium, such as Dulbecco's modified Eagle's
medium plus insulin. All experiments were done with clonal cultures of HMSC to insure that observed growth responses were
always those of muscle cells.
This research was supported by a grant from the Muscular, Dystrophy Association.
Editor's statement This article describes the optimization of both the basal nutrient medium and growth factor requirements
for human muscle cells in vitro. This system is critical for studies of normal muscle cell and molecular biology, as well
as for understanding diseases of muscle such as Duchenne, Muscular Dystrophy. 相似文献
8.
J. Van Den Ende 《Plant and Soil》1991,133(1):65-74
The products of activities of calcium and sulphate were calculated for solutions of 75 glasshouse soils. The majority of these products was found to be higher than the solubility product of gypsum, thus indicating that these soil solutions were possibly supersaturated. In another investigation, soil solutions were examined to determine whether such high activity products could be really attributed to supersaturation. By means of ultracentrifuging of solutions of glasshouse soils, it could be established that the solutions were practically free of sulphate-bearing colloidal particles. Some solutions contained calcium-bearing colloidal particles, but the quantities of calcium contained in these particles were too small to substantially influence the calcium activity. Addition of gypsum crystals to soil solutions led to crystallization of so much calcium and sulphate that the products of the activities of calcium and sulphate dropped from values that can be listed as high to values approaching the solubility product of gypsum. The results obtained demonstrate the occurrence of supersaturation of soil solutions with respect to gypsum. It is further postulated that the presence of humic substances in the soil solution is responsible for this supersaturation. The possible occurrence of supersaturation with respect to gypsum in soils other than glasshouse soils is discussed. 相似文献
9.
Piero Pollesello Renato Toffanin Erminio Murano Roberto Rizzo Sergio Paoletti Bjarne J. Kvam 《Journal of applied phycology》1992,4(2):149-155
Lipid extracts of the red algaGracilaria longa were studied by1H- and13C-NMR spectroscopy. Peaks in the13C-NMR spectra attributable to sterols, chlorophylls and carotenoids allowed free and acylated cholesterol, chlorophylla and lutein to be identified as the most abundant components of these classes. A content of 0.5 ± 0.1 μmoles of total cholesterol/g
wet alga was estimated from the1H-NMR spectrum, which also allowed the determination of the phosphatidylcholine/total lipid molar ratio (9.5 ± 0.5%). The13C-NMR spectroscopic experiments provided information on the position of the double bonds on the fatty acid residues. A comparison
between NMR spectra of lipid extracts obtained for wet and dried alga showed that the alga undergoes both a dramatic peroxidation
and some glycolipid degradation during the drying process. 相似文献
10.
The follicular dynamics of 112 mares treated with an equine pituitary extract were studied. Follicles >10 mm in diameter at day 15 post-ovulation appeared to represent the follicles which were induced with pituitary extract to grow and ovulate. This was shown by the greater number of >10 mm follicles in mares which subsequently had higher ovulation rates and by the subsequent decrease in number of small follicles (<20 mm) which corresponded with the increase in number of large follicles (>/=20 mm). The difference in diameter (mm) between the largest and second largest follicle on day 15 post-ovulation was greater (P<0.05) for extract-treated mares which subsequently had single ovulations than for extract-treated mares which subsequently had multiple ovulations (7.7 +/-1.5 vs 2.8 +/-0.6). The observed ratio of bilateral to unilateral multiple ovulations was not different (P>0.1) from the expected ratio which was calculated on the assumption that side of ovulation occurred independently (59:19 vs 62:16, observed vs expected). 相似文献