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101.
Alberto Bargagna Pietro Schenone Francesco Bondavalli Mario Longobardi 《Journal of heterocyclic chemistry》1980,17(1):33-37
Cycloaddition of sulfene to N,N-disubstituted 4-amino-3-methyl-3-buten-2-ones (III) occurred in fair to good yield only in the case of aliphatic N-substitution to give 4-dialkylamino-3,4-dihydro-5,6-dimethyl-1,2-oxathiin 2,2-dioxides, whereas N,N-disubstituted 1-amino-1-penten-3-ones (II) did not react at all. Cycloaddition of dichloroketene to II, III and N,N-disubstituted 4-amino-3-buten-2-ones occurred only in the case of the methylphenylamino derivative, giving in good to moderate yield 6,(5)(di)alkyl-3,3-dichloro-3,4-dihydro-4-methylphenylamino-2-Hpyran-2-ones, which were dehydrochlorinated with DBN to 6,(5)(di)alkyl-3-chloro-4-methylphenylamino-2H-pyran-2-ones. 相似文献
102.
Alegría Carrasco-Pancorbo Sonia Cortacero-Ramírez Alberto Fernández-Gutiérrez 《Talanta》2007,71(1):397-405
Two different families of compounds, i.e., phenolic and amino acids have been separated by capillary electrophoresis using a physically adsorbed polymer as capillary coating. The polymer used was N,N-dimethylacrylamide-ethylpyrrolidine methacrylate (DMA-EpyM) and it provided an stable coating by only flushing the capillary with a DMA-EpyM aqueous solution for 2 min between runs. The usefulness of this procedure has been demonstrated through the fast analysis of different families of solutes. Two different detection systems, diode-array detector and laser-induced fluorescence, have been used to determine phenolic acids and derivatized amino acids with fluorescein isothiocyanate, respectively. The main factors affecting reversal of electroosmotic flow (EOF) such as pH, type and concentration of buffer, and concentration and influence of organic solvents, as well as all the instrumental conditions were studied and optimized for both families of compounds. 相似文献
103.
The silanol acidity of Waters Resolve C18, Waters Resolve silica, Waters Symmetry C18, Waters Symmetry silica, Waters XTerra MS C18 and underivatized XTerra columns has been measured from the retention of LiNO3 with a methanol/water (60:40) mobile phase buffered to different pH values. The Li+ cation is retained by cationic exchange with the background cation of the mobile phase (Na+) through the ionized silanols. The number of active silanols increases in the order: XTerra MS C18 < Symmetry C18 < underivatized XTerra < Resolve C18 < Resolve silica approximately equal to Symmetry silica. XTerra MS C18 does not present any residual silanol acidity up to s(s)pH 10.0 (pH in 60% methanol) as measured by LiNO3. The underivatized XTerra packing and Symmetry C18 present active silanols only at s(s)pH values higher than 7.0. For the other three columns, two different types of silanols with different acidity (s(s)pKa values about 3.5-4.6 and 6.2-6.8, respectively) have been observed. Symmetry C18 shows evidence of the presence of active basic sites that retain NO3- by anionic exchange. 相似文献
104.
Francesca Benedini Giorgio Bertolini Francesco Ferrario Angelo Motti Alberto Sala Flavio Somenzi 《Journal of heterocyclic chemistry》1995,32(1):103-107
The preparation and the physico-chemical characterization of 2H-pyrido[2,3-e]-1,3-oxazine-2,4(3H)-diones, 2H-pyrido[4,3-e]-1,3-oxazine-2,4(3H)-diones, 2H-pyrido[4,3-e]-1,3-oxazin-4(3H)-ones, 2H-thieno[2,3-e]-1,3-oxazin-4(3H)-ones and 2H-thieno[3,4-e]-1,3-oxazine-2,4(3H)-diones are reported. 相似文献
105.
Binding and condensation of plasmid DNA onto functionalized carbon nanotubes: toward the construction of nanotube-based gene delivery vectors 总被引:10,自引:0,他引:10
Singh R Pantarotto D McCarthy D Chaloin O Hoebeke J Partidos CD Briand JP Prato M Bianco A Kostarelos K 《Journal of the American Chemical Society》2005,127(12):4388-4396
Carbon nanotubes (CNTs) constitute a class of nanomaterials that possess characteristics suitable for a variety of possible applications. Their compatibility with aqueous environments has been made possible by the chemical functionalization of their surface, allowing for exploration of their interactions with biological components including mammalian cells. Functionalized CNTs (f-CNTs) are being intensively explored in advanced biotechnological applications ranging from molecular biosensors to cellular growth substrates. We have been exploring the potential of f-CNTs as delivery vehicles of biologically active molecules in view of possible biomedical applications, including vaccination and gene delivery. Recently we reported the capability of ammonium-functionalized single-walled CNTs to penetrate human and murine cells and facilitate the delivery of plasmid DNA leading to expression of marker genes. To optimize f-CNTs as gene delivery vehicles, it is essential to characterize their interactions with DNA. In the present report, we study the interactions of three types of f-CNTs, ammonium-functionalized single-walled and multiwalled carbon nanotubes (SWNT-NH3+; MWNT-NH3+), and lysine-functionalized single-walled carbon nanotubes (SWNT-Lys-NH3+), with plasmid DNA. Nanotube-DNA complexes were analyzed by scanning electron microscopy, surface plasmon resonance, PicoGreen dye exclusion, and agarose gel shift assay. The results indicate that all three types of cationic carbon nanotubes are able to condense DNA to varying degrees, indicating that both nanotube surface area and charge density are critical parameters that determine the interaction and electrostatic complex formation between f-CNTs with DNA. All three different f-CNT types in this study exhibited upregulation of marker gene expression over naked DNA using a mammalian (human) cell line. Differences in the levels of gene expression were correlated with the structural and biophysical data obtained for the f-CNT:DNA complexes to suggest that large surface area leading to very efficient DNA condensation is not necessary for effective gene transfer. However, it will require further investigation to determine whether the degree of binding and tight association between DNA and nanotubes is a desirable trait to increase gene expression efficiency in vitro or in vivo. This study constitutes the first thorough investigation into the physicochemical interactions between cationic functionalized carbon nanotubes and DNA toward construction of carbon nanotube-based gene transfer vector systems. 相似文献
106.
Samples in the system Lu2−xYxSi2O7 (0?x?2) have been synthesized following the sol-gel method and calcined to 1300 °C, a temperature at which the β-polymorph is known to be the stable phase for the end-members Lu2Si2O7 and Y2Si2O7. The XRD patterns of all the compositions studied are compatible with the structure of the β-polymorph. Unit cell parameters are calculated as a function of composition from XRD patterns. They show a linear change with increasing Y content, which indicates a solid solubility of β-Y2Si2O7 in β-Lu2Si2O7 at 1300 °C. 29Si MAS NMR spectra of the different members of the system agree with the XRD results, showing a linear decrease of the 29Si chemical shift with increasing Y content. Finally, a correlation reported in the literature to predict 29Si chemical shifts in silicates is applied here to obtain the theoretical variation in 29Si chemical shift values in the system Lu2Si2O7-Y2Si2O7 and the results compare favorably with the values obtained experimentally. 相似文献
107.
We have performed a comparative study of the electronic properties of six different electron-doped metal-phthalocyanine (MPc) compounds (ZnPc, CuPc, NiPc, CoPc, FePc, and MnPc), in which the electron density is controlled by means of potassium intercalation. Despite the complexity of these systems, we find that the nature of the underlying molecular orbitals produces observable effects in the doping dependence of the electrical conductivity of the materials. For all the MPc's in which the added electrons are expected to occupy orbitals centered on the ligands (ZnPc, CuPc, and NiPc), the doping dependence of the conductivity has an essentially identical shape. This shape is different from that observed in MPc materials in which electrons are also added to orbitals centered on the metal atom (CoPc, FePc, and MnPc). The observed relation between the macroscopic electronic properties of the MPc compounds and the properties of the molecular orbitals of the constituent molecules clearly indicates the richness of the alkali-doped metal-phthalocyanines as a model class of compounds for the investigation of the electronic properties of molecular systems. 相似文献
108.
A series of cyano-bridged binuclear mixed valence complexes of the general formula M-Ru(III)(NH(3))(4)pyCOOH [pyCOOH = isonicotinic acid; M = cis-Ru(bpy)(2)(CN)(2), 1 (bpy = 2,2' bipyridine); trans-Ru(py)(4)(CN)(2), 2 (py = pyridine); [Ru(CN)(6)](4)(-), 3; [Fe(CN)(6)](4)(-), 4] have been prepared and anchored through the carboxylic function to nanocrystalline TiO(2) or SnO(2) electrodes. The complexes display a reversible electrochromic behavior in the range of applied potential from -0.5 to +0.5 V, versus SCE. Tuning of the electronic transitions in the visible and near-infrared spectral regions is achieved through changes of the solvent and of the cyano-bridged metal moiety M. 相似文献
109.
Freiría A Bastida R del Carmen Fernández-Fernández M Macías A Valencia L Vicente M 《Inorganic chemistry》2005,44(4):930-934
We report here the first pentanuclear Ba(II) complex of a new tri-aza, tri-oxa macrocycle with two carboxymethyl "arms" pending from two N atoms, H2L2. The crystal structure corresponds to the formula [Ba5(H0.375L2)4(ClO4)(CH3CH2OH)(H2O)2](ClO4)2.5 x 9.5H2O and reveals the presence of four molecules of the ligand surrounding five Ba(II) ions, giving rise to an unusual structure with the metal ions inside a spherical organic cavity. 相似文献
110.
Klärner FG Kahlert B Boese R Bläser D Juris A Marchioni F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(11):3363-3374
Novel molecular clips with anthracene sidewalls (1 a-c) were synthesized; they form stable host-guest complexes with a variety of electron-deficient aromatic and quinoid molecules. According to single-crystal structure analyses of clip 1 c and 1,2,4,5-tetracyanobenzene (TCNB) complex 14@1 b, the clips' anthracene sidewalls have to be compressed substantially during the complex formation to provide attractive pi-pi interactions between the aromatic guest molecule and the two anthracene sidewalls in the complex. The compression and expansion of aromatic sidewalls are calculated by molecular mechanics to be low-energy processes, so the energy required for compression of the anthracene sidewalls during complex formation is apparently overcompensated by the gain in energy resulting from the attractive pi-pi interactions. The finding that complexes of the clips 1 a-c are more stable than those of the corresponding clips 2 a-c can be explained in terms of the larger van der Waals contact surfaces of the anthracene sidewalls in 1 a-c (relative to the naphthalene sidewalls in 2 a-c). Color changes resulting from charge-transfer (CT) bands are observed in complex formation by 1 a-c: from colorless to red or purple with TCNB (14), and from yellow to green with 2,4,7-trinitro-9-fluorenone TNF (17). Independently, the host 1 b and guest 14 fluoresce from their respective excited singlet states, whilst in the complex 14@1 b the charge-transfer state quenches the higher-energy singlet states of the two components, and as a result luminescence is only observed from this new CT state. To the best of our knowledge, complex 14@1 b is the first example of CT luminescence from a host-guest complex. The binding constant determined for the formation of the TCNB complex 14@1 b from a UV/Vis titration experiment (Ka = 12 400 m(-1)) agrees well with the value (K(a) = 12 800 m(-1)) obtained by 1H NMR titration. 相似文献