排序方式: 共有52条查询结果,搜索用时 31 毫秒
1.
2.
Wen Li Edita Mjekiqi Wessel Douma Xin Wang Dr. Oksana Kavatsyuk Prof. Dr. Ronnie Hoekstra Dr. Jean-Christophe Poully Dr. Thomas Schlathölter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):16114-16119
Vacuum ultraviolet photoionization of a gas-phase oligonucleotide anion leads to the formation of a valence hole. This hole migrates towards an energetically favorable site where it can weaken bonds and ultimately lead to bond cleavage. We have studied Vacuum UV photoionization of deprotonated oligonucleotides containing the human telomere sequence dTTAGGG and G-quadruplex structures consisting of four dTGGGGT single strands, stabilized by NH4+ counter ions. The oligonucleotide and G-quadruplex anions were confined in a radiofrequency ion trap, interfaced with a synchrotron beamline and the photofragmentation was studied using time-of-flight mass spectrometry. Oligonucleotide 12-mers containing the 5'-TTAGGG sequence were found to predominantly break in the GGG region, whereas no selective bond cleavage region was observed for the reversed 5'-GGGATT sequence. For G-quadruplex structures, fragmentation was quenched and mostly non-dissociative single and double electron removal was observed. 相似文献
3.
L’ubomíra Balková Edita Pelantová Wolfgang Steiner 《Monatshefte für Mathematik》2008,155(3-4):251-263
An infinite word has the property R m if every factor has exactly m return words. Vuillon showed that R 2 characterizes Sturmian words. We prove that a word satisfies R m if its complexity function is (m ? 1)n + 1 and if it contains no weak bispecial factor. These conditions are necessary for m = 3, whereas for m = 4 the complexity function need not be 3n + 1. A new class of words satisfying R m is given. 相似文献
4.
Cellulose liquefaction in acidified ethylene glycol 总被引:3,自引:0,他引:3
Wood pulp cellulose was used in a study of its catalyzed liquefaction in the presence of ethylene glycol, p-toluene sulfonic acid monohydrate or sulphuric acid being the catalysts. For this study, microcrystalline cellulose, Whatman
filter paper no. 1 and cotton linters with molar masses of 76,000, 699,000 and 1,910,000 g mol−1, respectively were used. This liquefaction was studied by gravimetric determinations, by X-ray diffraction analysis of the
residual cellulose and by monitoring of the molar mass decrease over different time intervals, using size-exclusion chromatography.
The disordered regions, even of cellulose with the highest molar mass degraded in the initial minute of liquefaction. However,
the highly ordered cellulose regions remained relatively stable for a longer time. None the less, partial degradation of the
highly ordered regions of the cellulose was achieved. 相似文献
5.
6.
7.
The objective of present study was to establish and compare the contents of secondary metabolites of two Hypericum species, H. perforatum and H. maculatum, native to Lithuania, and to evaluate factors predetermining their variation with some practical implications for utilization and conservation. The HPLC analysis of the ethanolic extracts of the studied species showed some regularity in their composition. Both species contained chlorogenic acid, hyperoside, quercitrin, quercetin and hypericin. The presence of rutin and hyperforin was observed only in H. perforatum. The quantitative analysis showed higher content of quercitrin in H. perforatum, than in H. maculatum, whereas the differences in the contents of quercetin, hypericin and chlorogenic acid were not statistically significant between the species. H. maculatum contained a significantly higher content of hyperoside than H. perforatum. The data on phytochemical analysis suggest almost equivalent use of both H. perforatum and H. maculatum extracts in the food industry, cosmetics and pharmaceutics. 相似文献
8.
Anna Sopková Jozef Chomič Edita Matejěíková 《Monatshefte für Chemie / Chemical Monthly》1971,102(4):961-963
Zusammenfassung Durch Ersetzung des Cadmiums im Clathrat Cden[Ni(CN)4]·2C6H6 wurden drei Verbindungen des TypsM(en)
m[Ni(CN)4]·nC6H6 (M
2+=Ni, Cu, Zn;m=2–3;n=0.14–0.28) hergestellt und charakterisiert.
Synthesis of ethylendiamine-(metal II)-tetracyanoniccolate dibenzene clathrate compounds
Replacing cadmium ion in Cden[Ni(CN)4]·2C6H6 clathrate compound three compounds ofM(en) m[Ni(CN)4]·nC6H6 type (M 2+=Ni, Cu, Zn;m=2–3;n=0.14–0.28) were prepared and characterized.相似文献
9.
L’ubomíra Balková Karel Klouda Edita Pelantová 《Letters in Mathematical Physics》2009,87(1-2):181-195
Classical crystals are solid materials containing arbitrarily long periodic repetitions of a single motif. In this Letter, we study the maximal possible repetition of the same motif occurring in β-integers—one dimensional models of quasicrystals. We are interested in β-integers realizing only a finite number of distinct distances between neighboring elements. In such a case, the problem may be reformulated in terms of combinatorics on words as a study of the index of infinite words coding β-integers. We will solve a particular case for β being a quadratic non-simple Parry number. 相似文献
10.