排序方式: 共有64条查询结果,搜索用时 46 毫秒
31.
Dr. Mateja Klika Škopić Christian Gramse Dr. Rosario Oliva Sabrina Pospich Laura Neukirch Magiliny Manisegaran Prof. Dr. Stefan Raunser Prof. Dr. Roland Winter Prof. Dr. Ralf Weberskirch Dr. Andreas Brunschweiger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(39):10048-10057
The development of DNA-compatible reaction methodologies is a central theme to advance DNA-encoded screening library technology. Recently, we were able to show that sulfonic acid-functionalized block copolymer micelles facilitated Brønsted acid-promoted reactions such as the Povarov reaction on DNA-coupled starting materials with minimal DNA degradation. Here, the impact of polymer composition on micelle shape, and reaction conversion was investigated. A dozen sulfonic acid-functionalized block copolymers of different molar mass and composition were prepared by RAFT polymerization and were tested in the Povarov reaction, removal of the Boc protective group, and the Biginelli reaction. The results showed trends in the polymer structure-micellar catalytic activity relationship. For instance, micelles composed of block copolymers with shorter acrylate ester chains formed smaller particles and tended to provide faster reaction kinetics. Moreover, fluorescence quenching experiments as well as circular dichroism spectroscopy showed that DNA-oligomer-conjugates, although highly water-soluble, accumulated very effectively in the micellar compartments, which is a prerequisite for carrying out a DNA-encoded reaction in the presence of polymer micelles. 相似文献
32.
Binding of three different bacteriophages (phages), namely T7, lambda and M13 on methacrylate monoliths was investigated. Phage M13 exhibited the highest dynamic binding capacity of 4.5×10(13) pfu/mL while T7 and lambda showed capacity of 1×10(13) pfu/mL, all corresponding to values of around 1mg/mL. Interestingly, capacity for lambda phage was increased 5-fold by increasing NaCl concentration in a loaded sample from 0 to 0.2M while there was a constant capacity decrease for T7 and M13 phages. Under optimal conditions, recovery for all three phages approached 100%. Measurement of a pressure drop increase during loading enabled estimation of adsorbed phage layer thickness. At a maximal capacity it was calculated to be around 50 nm for T7 phage and 60 nm for lambda phage matching closely capside size thus indicating monolayer adsorption while 80 nm layer thickness was estimated for M13 phage showing its orientation along the pore. 相似文献
33.
Mateja Grašič 《Linear and Multilinear Algebra》2013,61(6):671-685
We show that the Jordan algebra 𝒮 of symmetric matrices with respect to either transpose or symplectic involution is zero product determined. This means that if a bilinear map {.,?.} from 𝒮?×?𝒮 into a vector space X satisfies {x, y}?=?0 whenever x?○?y?=?0, then there exists a linear map T : 𝒮?→?X such that {x,?y}?=?T(x?○?y) for all x, y?∈?𝒮 (here, x?○?y?=?xy?+?yx). 相似文献
34.
Sebastian Groß Fabian Panter Domen Pogorevc Carsten E. Seyfert Selina Deckarm Chantal D. Bader Jennifer Herrmann Rolf Müller 《Chemical science》2021,12(35):11882
The development of new antibiotics is imperative to fight increasing mortality rates connected to infections caused by multidrug-resistant (MDR) bacteria. In this context, Gram-negative pathogens listed in the WHO priority list are particularly problematic. Darobactin is a ribosomally produced and post-translationally modified bicyclic heptapeptide antibiotic selectively killing Gram-negative bacteria by targeting the outer membrane protein BamA. The native darobactin A producer Photorhabdus khanii HGB1456 shows very limited production under laboratory cultivation conditions. Herein, we present the design and heterologous expression of a synthetically engineered darobactin biosynthetic gene cluster (BGC) in Escherichia coli to reach an average darobactin A production titre of 13.4 mg L−1. Rational design of darA variants, encoding the darobactin precursor peptide with altered core sequences, resulted in the production of 13 new ‘non-natural’ darobactin derivatives and 4 previously hypothetical natural darobactins. One of the non-natural compounds, darobactin 9, was more potent than darobactin A, and showed significantly improved activity especially against Pseudomonas aeruginosa (0.125 μg mL−1) and Acinetobacter baumannii (1–2 μg mL−1). Importantly, it also displayed superior activity against MDR clinical isolates of E. coli (1–2 μg mL−1) and Klebsiella pneumoniae (1–4 μg mL−1). Independent deletions of genes from the darobactin BGC showed that only darA and darE, encoding a radical forming S-adenosyl-l-methionine-dependent enzyme, are required for darobactin formation. Co-expression of two additional genes associated with the BGCs in hypothetical producer strains identified a proteolytic detoxification mechanism as a potential self-resistance strategy in native producers. Taken together, we describe a versatile heterologous darobactin platform allowing the production of unprecedented active derivatives in good yields, and we provide first experimental evidence for darobactin biosynthesis processes.Heterologous expression of a synthetically engineered darobactin gene cluster in E. coli yields new darobactin derivatives with improved anti-Gram-negative activity. Targeted gene deletions provide first insights into biosynthetic steps. 相似文献
35.
A k-uniform hypergraph with vertex set V and edge set E is called t-subset-regular if every t-element subset of V lies in the same number of elements of E. In this paper we show that a 1-subset-regular self-complementary 3-uniform hypergraph with n vertices exists if and only if n≥5 and n is congruent to 1 or 2 modulo 4. 相似文献
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37.
Hočevar Mateja Berginc Marko Topič Marko Krašovec Urša Opara 《Journal of Sol-Gel Science and Technology》2010,53(3):647-654
A titanium oxide layer used in a dye-sensitized solar cell (DSSC) has to meet two opponent properties to enable high conversion
efficiency: a large surface area (for high dye loading) and good connection between TiO2 grains (for efficient extraction of electrons toward the front contact). In order to meet a trade-off between these criteria
a preparation method for TiO2 paste formulation based on Pechini sol–gel method and commercial nanocrystalline TiO2 powder has been developed. A series of TiO2 pastes with different molar ratios between titanium isopropoxide, citric acid and ethylene glycol (1:X:4X) in the paste have been examined. The structure and morphology as well as cross-cut tests of deposited and sintered TiO2 layers have been analyzed. Results reveal that the paste with X = 8 exhibits the best properties, resulting in an overall conversion efficiency of DSSC under standard test conditions (100 mW/cm2, 25 °C, AM 1.5G) up to 6.6% for ionic liquid based electrolyte. 相似文献
38.
Mateja ajna 《组合设计杂志》2002,10(1):27-78
We show that the necessary conditions for the decomposition of the complete graph of odd order into cycles of a fixed even length and for the decomposition of the complete graph of even order minus a 1‐factor into cycles of a fixed odd length are also sufficient. © 2002 John Wiley & Sons, Inc. J Combin Designs 10: 27–78, 2002 相似文献
39.
Gutiérrez-Aguirre I Steyer A Banjac M Kramberger P Poljšak-Prijatelj M Ravnikar M 《Journal of chromatography. A》2011,1218(17):2368-2373
40.
Germ M Mazej Z Gaberscik A Häder DP 《Journal of photochemistry and photobiology. B, Biology》2002,66(1):37-46
The responses of two amphibious species, Batrachium trichophyllum and Potamogeton alpinus to different UV-B environments were studied. Plant material from natural environments, as well as from outdoor treatments was examined. In long-term outdoor experiments plants were grown under three different levels of UV-B radiation: reduced and ambient UV-B levels, and a UV-B level simulating 17% ozone depletion. The following parameters were monitored: contents of total methanol soluble UV-absorbing compounds and chlorophyll a, terminal electron transport system (ETS) activity and optimal and effective quantum yield of photosystem II. No effect of the different UV-B levels on the measured parameters was observed. The amount of UV-B absorbing compounds seems to be saturated, since no differences were observed between treatments and no increase was found in peak season, when natural UV-B levels were the highest. Physiological measurements revealed no harmful effects; neither on potential and actual photochemical efficiency, nor on terminal ETS activity. The contents of UV-B absorbing compounds were examined also in plant material sampled in low and high altitude environments during the growth season. Both species exhibited no seasonal dynamics of production of UV-absorbing compounds. The contents were variable and showed no significant differences between high and low altitude populations. 相似文献