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排序方式: 共有900条查询结果,搜索用时 46 毫秒
71.
The heterofermentative lactic acid bacterium Oenococcus oeni requires pantothenic acid for growth. In the presence of sufficient pantothenic acid, glucose was converted by heterolactic fermentation stoichiometrically to lactate, ethanol and CO2. Under pantothenic acid limitation, substantial amounts of erythritol, acetate and glycerol were produced by growing and resting bacteria. Production of erythritol and glycerol was required to compensate for the decreasing ethanol production and to enable the synthesis of acetate. In ribose fermentation, there were no shifts in the fermentation pattern in response to pantothenate supply. In the presence of pantothenate, growing O. oeni contained at least 10.2 microM HSCoA, whereas the HSCoA content was tenfold lower after growth in pantothenate-depleted media. HSCoA and acetyl-CoA are cosubstrates of phosphotransacetylase and acetaldehyde dehydrogenase from the ethanol pathway. Both enzymes were found with activities commensurate with their function in ethanol production during heterolactic fermentation. From the kinetic data of the enzymes and the HSCoA and acetyl-CoA contents, it can be calculated that, under pantothenate limitation, phosphotransacetylase, and in particular acetaldehyde dehydrogenase activities become limiting due to low levels of the cosubstrates. Thus HSCoA deficiency represents the major limiting factor in heterolactic fermentation of glucose under pantothenate deficiency and the reason for the shift to erythritol, acetate, and glycerol fermentation. 相似文献
72.
NMR experiments for the sign determination of homonuclear scalar and residual dipolar couplings 总被引:1,自引:0,他引:1
A modified version of the JHH-TOCSY experiment, `signed COSY', is presented that allows the determination of the sign of residual dipolar 1H-1H coupling constants with respect to the sign of one-bond 1H-X coupling constants in linear three-spin systems X-1H-1H, where X = 13C or 15N. In contrast to the original JHH-TOCSY experiments, the signs of J
HH couplings may be determined for CH2-CH2 moieties and for uniformly 13C/15N-labelled samples. In addition, sensitivity is enhanced, diagonal peaks are suppressed and cross peaks are observed only between directly coupled protons, as in a COSY spectrum. 相似文献
73.
Patrik Andersson Kerstin Nordstrand Maria Sunnerhagen Edvards Liepinsh Ivars Turovskis Gottfried Otting 《Journal of biomolecular NMR》1998,11(4):445-450
Spin-state selective experiments, HSQC-/ and CT-HMQC-/, are proposed for the simple and rapid measurement of scalar one-bond coupling constants in two-dimensional,1 H-detected 15N-1H or13 C-1H correlation experiments based on HSQC and HMQC schemes. Pairs of subspectra are obtained, containing either the high-field or the low-field component of the doublet representing the one-bond coupling constant. The subspectral editing procedure retains the full sensitivity of HSQC and HMQC spectra recorded without heteronuclear decoupling during data acquisition, with a spectral resolution similar to that of decoupled spectra. 相似文献
74.
75.
Patrik Andersson Bernard Gsell Beat Wipf Hans Senn Gottfried Otting 《Journal of biomolecular NMR》1998,11(3):279-288
An HMQC experiment is proposed, dubbed FHMQC, where water flip-back is achieved by a single water-selective pulse preceding the basic HMQC pulse sequence. The scheme is demonstrated with a 15N, 1H-HMQC spectrum of uniformly 15N/2H-labelled S. aureus DNA gyrase B with a molecular weight of 45 kDa for the unlabelled protein. The sensitivity of the experiment is improved compared to that of an FHSQC spectrum. It is further shown that the original FHSQC experiment can be shortened by the use of bipolar gradients. Relaxation times of different 15N magnetizations and coherences were measured. The new FHMQC scheme is implemented in 3D NOESY-15N-HMQC and 3D15 N-HMQC-NOESY-15N-HMQC pulse sequences which are demonstrated with a 24 kDa fragment of uniformly 15N/13C/2H-labelled S. aureus DNA gyrase B. 相似文献
76.
Markus Düchler Fritz Schmoll Franz Pfneisl Gottfried Brem Karl Schellander 《Biology of the cell / under the auspices of the European Cell Biology Organization》1998,90(2):199-205
We have established three independent ovine mammary epithelial cell lines which arose from primary cultures of ovine mammary epithelial cells by spontaneous immortalization. One of them, OMEC II, was characterised in greater detail. The cells grow rapidly on plastic dishes in medium containing 10% FCS without any requirement for additional growth factors or hormones. Immunofluorescence staining of this cell line showed expression of cytokeratin (46 kDa) and ZO-1, a tight-junction associated protein, but negative immunostaining for an anti-vimentin antibody. In confluent cell monolayers ‘domes’ became visible indicating the development of a polarised phenotype and the ability of directed secretion. When grown in collagen gels typical ducts with end-buds were observed. Treatment with lactogenic hormones increased the frequency of dome formation, but no expression of β-lactoglobulin was found. To our knowledge this is the first report on an ovine mammary epithelial cell line. 相似文献
77.
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79.
Siamak Ravanbakhsh Philip Liu Trent C. Bjordahl Rupasri Mandal Jason R. Grant Michael Wilson Roman Eisner Igor Sinelnikov Xiaoyu Hu Claudio Luchinat Russell Greiner David S. Wishart 《PloS one》2015,10(5)
Many diseases cause significant changes to the concentrations of small molecules (a.k.a. metabolites) that appear in a person’s biofluids, which means such diseases can often be readily detected from a person’s “metabolic profile"—i.e., the list of concentrations of those metabolites. This information can be extracted from a biofluids Nuclear Magnetic Resonance (NMR) spectrum. However, due to its complexity, NMR spectral profiling has remained manual, resulting in slow, expensive and error-prone procedures that have hindered clinical and industrial adoption of metabolomics via NMR. This paper presents a system, BAYESIL, which can quickly, accurately, and autonomously produce a person’s metabolic profile. Given a 1D 1H
NMR spectrum of a complex biofluid (specifically serum or cerebrospinal fluid), BAYESIL can automatically determine the metabolic profile. This requires first performing several spectral processing steps, then matching the resulting spectrum against a reference compound library, which contains the “signatures” of each relevant metabolite. BAYESIL views spectral matching as an inference problem within a probabilistic graphical model that rapidly approximates the most probable metabolic profile. Our extensive studies on a diverse set of complex mixtures including real biological samples (serum and CSF), defined mixtures and realistic computer generated spectra; involving > 50 compounds, show that BAYESIL can autonomously find the concentration of NMR-detectable metabolites accurately (~ 90% correct identification and ~ 10% quantification error), in less than 5 minutes on a single CPU. These results demonstrate that BAYESIL is the first fully-automatic publicly-accessible system that provides quantitative NMR spectral profiling effectively—with an accuracy on these biofluids that meets or exceeds the performance of trained experts. We anticipate this tool will usher in high-throughput metabolomics and enable a wealth of new applications of NMR in clinical settings. BAYESIL is accessible at http://www.bayesil.ca. 相似文献
80.
Katrin Spiesberger Florian Paulfranz Anton Egger Judith Reiser Claus Vogl Judith Rudolf-Scholik Corina Mayrhofer Ludger Grosse-Hovest Gottfried Brem 《PloS one》2015,10(10)