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101.
Hitzeroth G Vater J Franke P Gebhardt K Fiedler HP 《Rapid communications in mass spectrometry : RCM》2005,19(20):2935-2942
Streptocidins, a family of tyrocidine-like cyclic decapeptides, are an ideal demonstration object for the detection and in situ structure analysis of natural compounds directly in microbial cells using whole cell matrix-assisted laser desorption/ionization time-of-flight-mass spectrometry (MALDI-TOFMS), an emerging technique that can be used for rapid sensitive metabolic profiling of microorganisms. Five main members of the streptocidin family (A-E) were detected in Brevibacillus cells picked from agar plates and identified by in situ structure analysis with post-source decay MALDI-TOFMS. This efficient modern method allows the precise detection of metabolites within minutes without the need to isolate and purify the target compounds. The generated mass spectra are of similar quality to those obtained for the purified peptides. In addition, surface extracts were prepared by treating Brevibacillus cells with 70% acetonitrile in the presence of 0.1% trifluoroacetic acid and fractionated by high-resolution reversed-phase high-performance liquid chromatography (HPLC). In this way ten minor streptocidins were detected demonstrating the full biosynthetic variety of streptocidin production on the cellular level. The streptocidins differ from the well-known tyrocidines essentially in position 3 of the decapeptide chain by replacement of the aromatic amino acid (F/W) found in tyrocidines by L-leucine or L-valine. 相似文献
102.
G. Alexander L. Criegee H.C. Dehne K. Derikum R. Devenish G. Flügge G. Franke Ch. Gerke E. Hackmack P. Harms G. Horlitz Th. Kahl G. Knies E. Lehmann R. Schmitz R.L. Thompson U. Timm K. Wacker 《Physics letters. [Part B]》1978,76(5):652-656
The polarization of the f0(1270) and ?0(770) produced in the J/ψ decays into f0γ and ?0π0 are measured in e+e? collisions at 3.1 GeV. A fit to the f0 production and decay angular distributions yields the values A1/A0 = 0.6 ± 0.3 and A2/A0 = 0.3 ?1.6+0.6, where Aλ are the f0 helicity amplitudes. These results are in good agreement with the values predicted from a QCD two-gluon-exchange model. In addition an upper limit of 2.3 × 10?4 is obtained for the J/ψ → f′0(1514) γ decay branching ratio which implies Γ(J/ψ → f′γ)/Γ(J/ψ → f0γ) ? 0.12 ± 0.05. 相似文献
103.
104.
S. Franke S. Hildebrandt J. Schwarzbauer M. Link W. Francke 《Fresenius' Journal of Analytical Chemistry》1995,353(1):39-49
GC/MS non target screening has been applied to water samples taken during 1992–1994 from the Elbe river and its tributaries Mulde, Saale, Weiße Elster, Schwarze Elster, and Havel. Based on full scan electron impact mass spectra and supplemented by extensive use of chemical ionisation and high resolution data as well as by synthetic reference compounds, several new classes of compounds, whose possible environmental effects are yet unknown at present, have been identified. Tetrachlorinated bis-(propyl)ethers are new among the most prominent contaminants throughout the Elbe river. The confluence with the Mulde river adds a variety of compounds, related to the chemistry of chloro- and nitroaromatics, azo dyes, benzanilides, carbamates, thiophosphates, and pesticides. The combined load of the Weiße Elster and Saale rivers carries oligoformals, oxathiamacrocycles, and dichloro- and trichloro-bis-(propyl)ethers, whereas chloropropylphosphates are introduced via the Schwarze Elster. The majority of these compounds, originating from sources at the tributaries, are still present at the mouth of the Elbe river. In addition to specific industrial emissions, a variety of more generally observed organic compounds like long chain aliphatics, sterols, phenylalkanes, and plasticizers as well as ubiquitous environmental trace pollutants like polycyclic aromatic hydrocarbons, chlorobenzenes, and hexachlorocyclohexane isomers have been encountered throughout the Elbe river drainage system.Part I: S. Franke, S. Hildebrandt, W. Francke, H. Reincks (1995) Naturwissenschaften 82: 80–83 相似文献
105.
106.
K. Fröhlich T. Franke R. Gellermann D. Hebert H. Jordan 《Isotopes in environmental and health studies》2013,49(9):355-360
This paper presents results of a study carried out in order to assess the applicability of 32Si for groundwater dating. Measurements of 32Si in soil samples of the unsaturated zone, of drainage waters and plant material give a basis for estimating the 32Si initial concentration in groundwater. Different aquifers with groundwater of young and moderate ages have been selected for groundwater studies. For obtaining independent age information tritium was found to be a suitable reference isotope. A quantitative interpretation of the 32Si data is generally complicated by geochemical processes, preferably in the unsaturated zone. Favourable conditions concerning the use of 32Si in hydrogeology seem to exist in phreatic sandy aquifers, in limestone aquifers, and, depending on the thickness and composition of the unsaturated zone, in sandstone aquifers. Further improvements of the 32Si method needs a better understanding of the geochemical processes affecting this isotope. 相似文献
107.
John E. Franke Abdul-Aziz Yakubu 《Journal of Difference Equations and Applications》2013,19(3):235-249
A discrete multi-species size-structured competition model is considered. By using decreasing growth functions, we achieve the self-regulation of species. We develop various biologically significant conditions for global convergence to the extinction state of the dominated species in the competitive system. With an example we illustrate coexistence in a chaotic supr transient. The chaotic attractor has an unusual pulsating nature. 相似文献
108.
Nicholas C. Johnson Angela C. Turrou Brandon G. McMillan Mary C. Raygoza Megan L. Franke 《Mathematical Thinking and Learning》2013,15(4):237-264
ABSTRACTCapturing the breadth and variety of children’s understanding is critical if studies of children’s mathematical thinking are to inform policy and practice in early childhood education. This article presents an investigation of young children’s counting. Detailed coding and analyses of assessment interviews with 476 preschoolers revealed understandings that would be overlooked by solely assessing the accuracy of their responses. In particular, many children demonstrated understandings of counting principles on a challenging task that were not captured by other, simpler tasks. We conclude that common approaches to capturing young children’s mathematical understanding are likely underestimating their capabilities. This study contributes to researchers’ understanding of what making sense of counting looks and sounds like for preschool age children (3–5 years), the development and relations among counting principles (one-to-one, cardinal, and patterns of the number sequence), and the affordances of challenging, open-ended tasks. We close by considering the implications of recognizing and building from what children know and can do for researchers, practitioners, and policymakers. 相似文献
109.
Franke KJ Schulze G Henningsen N Fernández-Torrente I Pascual JI Zarwell S Rück-Braun K Cobian M Lorente N 《Physical review letters》2008,100(3):036807
Codeposition of C60 and the three-dimensional molecular hydrocarbon 1,3,5,7-tetraphenyladamantane (TPA) on Au(111) leads to the spontaneous formation of molecular nanostructures in which each fullerene is locked into a specific orientation by three surrounding TPA. Scanning tunneling spectroscopy shows that the electronic coupling of C60 with the surface is significantly reduced in these nanostructures, enhancing the free-molecule properties. As evidenced by density functional theory simulations, the nanostructures are stabilized by 18 local electrostatic forces between C60 and TPA, resulting in a lifting of the C60 cage from the surface. 相似文献
110.
Maurice Dörr Sebastian Lips Prof. Dr. Carlos Alberto Martínez-Huitle Dr. Dieter Schollmeyer Prof. Dr. Robert Franke Prof. Dr. Siegfried R. Waldvogel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7835-7838
We report an innovative, sustainable and straightforward protocol for the synthesis of N,N-diarylamides equipped with nonprotected hydroxyl groups by using electrosynthesis. The concept allows the application of various substrates furnishing diarylamides with yields up to 57 % within a single and direct electrolytic protocol. The method is thereby easy to conduct in an undivided cell with constant current conditions offering a versatile and short-cut alternative to conventional pathways. 相似文献