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31.
Rozhon W Petutschnig E Wrzaczek M Jonak C 《Analytical and bioanalytical chemistry》2005,382(7):1620-1627
Salicylic acid (SA) is an important signaling compound in plants and is involved in various defense responses. Here we report a new method for quantification of free and total soluble SA in Arabidopsis thaliana with 5-fluorosalicylic acid (5-FSA) as internal standard. The SA was isolated from leaf extracts by solid-phase extraction with phenyl-phase cartridges and selectively eluted as the cationic iron(III)-complex. Recoveries of SA and 5-FSA were equal and exceeded 90%. Free SA was subsequently released from the iron(III)-complex by addition of 2,2-bipyridyl and high-performance anion-exchange chromatography was performed on an NH2 column. The SA appeared as last peak with a retention time of 15 min, baseline-separated from other substances. On-line detection was performed fluorimetrically for both SA and 5-FSA at an excitation wavelength of 300 nm and an emission wavelength of 410 nm, because both substances give similar fluorescence spectra. The detection limit for SA was 5 ng g–1 FW for a sample size of 100 mg. Thus the main advantages of the method are highly selective sample preparation, increased sensitivity, reduced analysis time compared with reversed-phase HPLC, and use of a novel internal standard detectable under the same conditions as SA. The techniques described are applicable to other plant materials. 相似文献
32.
F. Nastase Ioan Stamatin Claudia Nastase D. Mihaiescu A. Moldovan 《Progress in Solid State Chemistry》2006,34(2-4):191
In the present work, we explore the possibility to deposit polyaniline–silicon dioxide (PAni–SiO2) and polythiophene–silicon dioxide (PTh–SiO2) nanocomposites through a plasma polymerization route. The films were generated by spraying of mixtures of nano-sized silica particles dispersed in the liquid monomer into a plasma stream of the DC-plasma discharge reactor. The silica in the resulted polymer matrix changes the conduction mechanisms varying from ohmic to ballistic and traps inducing the space charged limited currents (SCLC). The silica modifies the morphology and composition of the deposited films. 相似文献
33.
Luis A.?León Rafael?Notario Jairo?QuijanoEmail author Ederley?Vélez Claudia?Sánchez J. Camilo?Quijano Nouria?Al-Awadi 《Theoretical chemistry accounts》2003,110(6):387-394
Theoretical studies on the thermolysis in the gas phase of 4-arylideneimino-1,2,4-triazol-3(2H)-ones and 4-arylideneimino-1,2,4-triazol-3(2H)-thiones were carried out using density functional theory methods, at the B3LYP/6-31G(d) and B3LYP/6-311+G(2d,p) levels of theory. The proposed reaction mechanism occurs in one step, leading to the formation of 3-hydroxy-(2H)-1,2,4-triazole or 3-mercapto-(2H)-1,2,4-triazole and a 4-substituted benzonitrile, via a six-membered cyclic transition state. The progress of the reactions was followed by means of the Wiberg bond indices. The results indicate that the transition states have character intermediate between reactants and products, and the calculated synchronicities show that the reactions are slightly asynchronous, in the case of triazolones, and show a higher asynchronicity in the case of triazolthiones. The bond-breaking processes are slightly more advanced than the bond-forming ones, indicating a small bond deficiency in the transition states. Kinetic and activation parameters for the reactions studied have been calculated and compared with available experimental data.From the Proceedings of the 28th Congreso deQuímicos Teóricos de Expresión Latina (QUITEL 2002) 相似文献
34.
Herforth C Wiesner J Franke S Golisade A Jomaa H Link A 《Journal of combinatorial chemistry》2002,4(4):302-314
We have investigated the in vitro antimalarial activity of a new series of adenosine derivatives. The results show that N(6)-(1-naphthylmethyl)-5'-deoxy-5'-(amido)adenosines as well as N(6)-(4-phenylbenzyl)-5'-deoxy-5'-(amido)adenosines display significant activity against the malaria-causing parasites, with the sterically demanding bisubstituted species reported being active in most cases in the low-micromolar range. The novel compounds with unusual substitution pattern were obtained applying an efficient convergent polymer-assisted solution-phase (cPASP) synthesis protocol. Thus, we were able to prepare a series of substituted derivatives in parallel that would have been difficult to synthesize by standard techniques. The scope and limitations of the synthetic methodology are discussed. 相似文献
35.
36.
Quagliotto P Viscardi G Barolo C D'Angelo D Barni E Compari C Duce E Fisicaro E 《The Journal of organic chemistry》2005,70(24):9857-9866
[reaction: see text] In this work, we report the synthesis of a new series of glucocationic surfactants, a class of surfactants we introduced very recently. The preparation of the surfactants is based on the synthesis of the 2-bromoethyl-2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside, whose preparation was studied in order to improve yields and stereoselectivity of this key intermediate. These glucocationic amphiphiles were prepared and studied as a model of cationic surfactants marked with a carbohydrate moiety. The use of carbohydrates as markers on cationic lipids was recently introduced to induce recognition by specific receptors, present on the surface of cell membranes. The chemicophysical characterization of these model structures can give more insight on the aggregation behavior. Conductivity and surface tension measurements were performed in order to characterize the compounds from the amphiphilic point of view. The results showed a different effect of the glucosidic moiety on the cmc value with respect to the glucopyridinium cationic surfactants. The surfactants also showed the tendency to form premicellar aggregates in solution when the hydrophobicity is raised. 相似文献
37.
Claudia Malvenuto 《Graphs and Combinatorics》1993,9(1):63-73
A conjecture of Stanley states that if the generating function of a posetP is symmetric, then in factP belongs to the family of posets induced by some skew shape /. In this paper we show that if the setL(P) of the linear extensions of a posetP is plactic-closed, thenP is a poset induced by a skew shape.Supported by LA CIM-UQAM and Consiglio Nazionale delle Ricerche 相似文献
38.
Bazzicalupi C Bencini A Berni E Bianchi A Ciattini S Giorgi C Maoggi S Paoletti P Valtancoli B 《The Journal of organic chemistry》2002,67(25):9107-9110
The synthesis of three new tris-macrocycles, containing three [12]aneN(4) (L1), [12]aneN(3)O (L2), or [14]aneN(4) (L3) moieties appended to a tren unit, is reported. The crystal structure of the [(Na(ClO(4))(6)) subset L1(2)H(13)]Na(6)Cl(2)(ClO(4))(12) compound shows the anionic cluster [Na(ClO(4))(6)](5)(-) assembled inside the cavity defined by two bowl-shaped polyammonium receptors, held by multiple charge-charge and hydrogen bond interactions. 相似文献
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40.
In the present investigation we report selection of the N-methyl-N-(tert.-butydimethylsilyl)trifluoroacetamide (MTBSTFA) reagent as the most comprehensive derivatization protocol among 17 tested reactions covering trifluoroacetylation, pentafluorobenzylation, methylations, and trimethylsilylations. MTBSTFA allowed easy and robust tert.-butyldimethylsilyl derivatization of 1-aminocyclopropane-1-carboxylic acid, indole-3-acetic acid, (+/-)-jasmonic acid, salicylic acid, (+/-)-abscisic acid, meta-topolin, and trans-zeatin. Detection limits as analysed by selected ion monitoring quadrupole GC-MS were 0.2, 0.01, 1.0, 0.02, 0.3, 0.3, and 0.9 pmol of injected substance, respectively. Analysis of gibberellic acid A3, trans-zeatin riboside and (+/-)-abscisic acid-beta-D-glucopyranosyl ester was best when coupled by splitting extracts and trimethysilylation. The MTBSTFA derivatization protocol was optimised, and validated. The preparation was insensitive to 2% residual water and to < or = 1 day storage at room temperature. The final scheme was highly reproducible and successfully applied to extracts from approximately 300 mg (fresh mass) of tobacco (Nicotiana tabacum) root and Arabidopsis thaliana seedling. 相似文献