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51.
Extraction of proteins from plant tissues for two-dimensional electrophoresis analysis 总被引:17,自引:0,他引:17
To increase the number of proteins detectable by two-dimensional electrophoresis (2-DE) in plants, we present a new procedure for extracting total proteins from plant tissue. This method avoids any loss of proteins in the course of sample preparation and results in two different fractions, one comprising mainly the cytoplasmatic proteins, the other one containing predominantly structure bond proteins. 2-DE patterns obtained from these two fractions show that the total number of different protein spots detected exceeds the degree of resolution commonly reported for plant proteins threefold. 相似文献
52.
Nowadays, about 150 natural products comprising an allenic or cumulenic structure are known. The chemistry of these compounds has turned out to be a very attractive and prolific area of interest: advances in the isolation and characterization of new allenic natural products have led to the establishment of efficient synthetic procedures which in many cases also open up an access to enantiomerically pure target molecules. Inspired by the intriguing biological activities of many allenic natural products, allene moieties are now systematically introduced in pharmacologically active classes of compounds (steroids, prostaglandins, amino acids, nucleosides). The functionalized allenes thus obtained often exhibit impressive activities as mechanism-based enzyme inhibitors, cytotoxic, or antiviral agents. A prerequisite for further developments in this field is the efficient stereoselective synthesis of allene derivatives. 相似文献
53.
Eberhard Bothe Helmut Gorner Joachim Opitz Dietrich Schulte-Frohlinde Aslam Siddiqi Malgorzata Wala 《Photochemistry and photobiology》1990,52(5):949-959
Double-stranded (ds) calf thymus DNA (0.4 mM), excited by 20 ns laser pulses at 248 nm, was studied in deoxygenated aqueous solution at room temperature and pH 6.7 in the presence of a sodium salt (10 mM). The quantum yields for the formation of hydrated electrons (phi c-), single-strand breaks (phi ssb) and double-strand breaks (phi dsb) were determined for various laser pulse intensities (IL). phi c- and phi ssb increase linearly with increasing IL; however, phi ssb has a tendency to reach saturation at high IL (greater than 5 X 10(6) Wcm-2). The ratio phi ssb/phi c-, representing the number of ssb per radical cation, is about 0.08 at IL less than or equal to 5 X 10(6) Wcm-2. For comparison, the number of ssb per OH radical reacting with dsDNA is 0.22. On going from argon to N2O saturation, phi ssb and phi dsb become larger by factors of approximately 5 and 10-15, respectively. This enhancement is produced by attack on DNA bases by OH radicals generated by N2O-scavenging of the photoelectrons. While phi ssb is essentially independent of the dose (Etot), phi dsb depends linearly on Etot in both argon- and N2O-saturated solutions. The linear dependence of phi dsb implies a square dependence of the number of dsb on Etot. This portion of dsb formation is explained by the occurrence of two random ssb, generated within a critical distance (h) in opposite strands. For both argon- and N2O-saturated solutions h was found to be of the order of 40-70 phosphoric acid diester bonds. On addition of electron scavengers such as 2-chloroethanol (or N2O plus t-butanol), phi dsb is similar to that in neat, argon-saturated solutions. Thus, hydrated electrons are not involved in the chemical pathway leading to laser-pulse-induced dsb of DNA. 相似文献
54.
Dilatometrical indication can be employed to the neutralizing reactions of polybasic acids and is demonstrated by the following acid-base couples: H2SO4/NaOH, H3PO4/NaOH and H5JO6/NaOH. With amounts between 0.5 and 4 mMol several, frequently all, equivalence points can be determined with a deviation of less than 0.2%. The determination of the changes of molar volume of the reactions depending on the concentrations allow conclusions as to the course of the reactions. 相似文献
55.
Preparation of β-hydroxyesters from isoxazolines. A selective Nibpy-catalyzed electrochemical method
Viviane F. CaetanoF.W.Joachim Demnitz Flamarion B. DinizRonaldo M. Mariz Jr. Marcelo Navarro 《Tetrahedron letters》2003,44(45):8217-8220
An electrocatalytic method for the reductive N-O cleavage of isoxazolines is described. Ni0bpy, generated in situ, was used to promote selective ring opening of 3-methoxy-5-phenylisoxazoline (1a) and 3-methoxy-[4,5]cyclohexylisoxazoline (1b). DMF and NaI were used as solvent and supporting electrolyte, and β-hydroxyesters 2a and 2b were obtained in high yields respectively, after acid hydrolysis. β-Hydroxynitriles 3a and 3b were also identified as side products. 相似文献
56.
Two new ligands consisting of bis(oxime) amine units tethered by a bridge have been synthesized. Their nickel chloride and nickel nitrate complexes have also been synthesized and characterized by X-ray crystallography, FTIR, mass spectrometry, and elemental analysis. One of these ligands, L1 (N,N,N',N'-tetra(1-propan-2-onyl oxime)-diamino-m-xylene), is always dinucleating, while the other ligand, L2 (N,N,N',N'-tetra(1-propan-2-onyl-oxime)-1,3-diaminopropane), shows an unusual anion dependence on the nuclearity. When nickel chloride is used, the ligand acts in a dinucleating manner and coordinates two nickels; however, when nickel nitrate is used, the ligand acts in a monodentate fashion and coordinates only one nickel. Once the mononuclear complex is formed, it is not possible to add a second nickel if Ni(NO(3))(2) is used as the nickel source; it is possible, however, to add a second nickel if NiCl(2) is used as the nickel source. The dinuclear complex can be converted to the mononuclear one by either using silver nitrate to exchange the chloride anions for nitrates or by dissolving the complex in water. Ni(2)(L1)Cl(4)(DMF)(2).DMF: orthorhombic, P2(1)2(1)2(1), a = 12.2524(11) A, b = 16.6145(15) A, c = 20.1234(19) A, V = 4096.5(6) A(3), Z = 4. [Ni(2)(L2)Cl(4)(DMF)](2).2DMF: triclinic, P-1, a = 12.5347(5) A, b = 12.5403(5) A, c = 14.3504(6) A, alpha = 67.348(1) degrees , beta = 69.705(1) degrees , gamma = 81.549(1) degrees , V = 1952.25(14) A(3), Z = 1. Ni(L2).(NO(3))(2): monoclinic, P2(1)/n, a = 9.6738(3) A, b = 30.2229(9) A, c = 15.8238(5) A, beta = 97.995(1) degrees , V = 4581.4(2) A(3), Z = 8. 相似文献
57.
Friedrich J Dolg M Gansäuer A Geich-Gimbel D Lauterbach T 《Journal of the American Chemical Society》2005,127(19):7071-7077
The mechanism of titanocene mediated 3-exo cyclizations was investigated by a combined theoretical and experimental study. A gradient corrected density functional theory (DFT) method has been scaled against titanocene dichloride, the parent butenyl radical, and in bond dissociation energy (BDE) calculations. The BP86 method using density fitting, and a basis set of triple-zeta quality emerged as a highly reliable tool for studying titanocene mediated radical reactions. The computational results revealed important kinetic and thermodynamic features of cyclopropane formation. Surprisingly, the beta-titanoxy radicals, the first intermediates of our investigations, were demonstrated to possess essentially the same thermodynamic stabilization as the corresponding alkyl radicals by comparison of the calculated BDEs. In contrast to suggestions for samarium mediated reactions, the cyclization was shown to be thermodynamically favorable in agreement with earlier kinetic studies. It was established that stereoselectivity of the cyclization is governed by the stability of the intermediates and thus the trans disubstituted products are formed preferentially. The observed ratios of products are in good to excellent agreement with the DFT results. By a combination of computational and experimental results, it was also shown that for the completion of the overall cyclopropane formation the efficiency of the trapping of the cyclopropylcarbinyl radicals is decisive. 相似文献
58.
Iron-silicon thin films have been characterized by means of analytical transmission electron microscopic methods. Under certain conditions — composition and annealing temperature — these films exhibit thermoelectric behavior. In particular, the morphology and phase formation which results from annealing of these films, and doping with oxygen and nitrogen, are of interest. The thermoelectric phase -FeSi2 is formed at temperatures above 500°C. This phase is transformed into electrically conducting phases at about 1000°C. A small oxygen content does not influence this crystallization process. If the oxygen content is higher than 15 atom-% the electrically conducting phases exist even at 500°C. The presence of a small nitrogen content inhibits the formation of the -FeSi2 phase. The development of silicon and iron nitrides is possible. 相似文献
59.
Hans‐Jürgen Holdt Holger Müller Alexandra Kelling Hans‐Joachim Drexler Thomas Müller Thomas Schwarze Uwe Schilde Ines Starke 《无机化学与普通化学杂志》2006,632(1):114-122
Mercury(II) Chloride and Iodide Complexes of Dithia‐ and Tetrathiacrown Ethers The complexes [(HgCl2)2((ch)230S4O6)] ( 1 ), [HgCl2(mn21S2O5)] ( 2 ), [HgCl2(ch18S2O4)] ( 3 ) and [HgI(meb12S2O2)]2[Hg2I6] ( 4 ) have been synthesized, characterized and their crystal structures were determined. In [(HgCl2)2((ch)230S4O6)] two HgCl2 units are discretely bonded within the ligand cavity of the 30‐membered dichinoxaline‐tetrathia‐30‐crown‐10 ((ch)230S4O6) forming a binuclear complex. HgCl2 forms 1 : 1 “in‐cavity” complexes with the 21‐membered maleonitrile‐dithia‐21‐crown‐7 (mn21S2O5) ligand and the 18‐membered chinoxaline‐dithia‐18‐crown‐6 (ch18S2O4) ligand, respectively. The 12‐membered 4‐methyl‐benzo‐dithia‐12‐crown‐4 (meb12S2O2) ligand gave with two equivalents HgI2 the compound [HgI(meb12S2O2)]2[Hg2I6]. In the cation [HgI(meb12S2O2)]+ meb12S2O2 forms with the cation HgI+ a half‐sandwich complex. 相似文献
60.
The absorption intensities of two infrared active lattice modes of crystalline N2O have been measured. Both the frequencies and intensities of the external modes of N2O have been found to be very similar to those of CO2, and most of the differences between the spectra of CO2 and N2O can be explained by the differences in the quadrupole moments. 相似文献