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91.
Fernandes C Santos IC Santos I Pietzsch HJ Kunstler JU Kraus W Rey A Margaritis N Bourkoula A Chiotellis A Paravatou-Petsotas M Pirmettis I 《Dalton transactions (Cambridge, England : 2003)》2008,(24):3215-3225
The quinazoline derivatives (3-chloro-4-fluorophenyl)quinazoline-4,6-diamine (2) and (3-bromophenyl)quinazoline-4,6-diamine (3) were labelled with (99m)Tc using the "4 + 1" mixed-ligand system [Tc(NS3)(CN-R)] and the tricarbonyl moiety fac-[Tc(CO)3]+. In the "4 + 1" approach the technetium(iii) is stabilized by a monodentate isocyanide bearing a quinazoline fragment (L1,L2 ) and by the tetradentate tripodal ligand tris(2-mercaptoethyl)-amine (NS3). In the "4 + 1" approach, 99mTc-labelling was performed in a two-step procedure, the complexes [Tc(NS3)(L1)] (7a) and [Tc(NS3)(L2)] (8a) being obtained in about 50-70% yield. In the tricarbonyl approach, the fac-[Tc(CO)3]+ unit is anchored by two different monoanionic chelators bearing the quinazoline derivatives (3-chloro-4-fluorophenyl)quinazoline-4,6-diamine (2) and (3-bromophenyl)quinazoline-4,6-diamine (3). Both chelators have a N2O donor atom set, but one contains a pyrazolyl ring (L5H) and the other contains a pyridine unit (L6H). In both cases the conjugation of the quinazoline to the chelator was done through the secondary amine of the potentially tridentate and monoanionic chelators, the corresponding 99mTc-complexes (10a, 11a) being obtained in quantitative yield. The identities of the 99mTc-labelled quinazolines (7a, 8a, 10a, 11a) were confirmed by comparison with the HPLC profiles of the analogous Re compounds (7, 8, 10, 11). All these Re complexes were characterized by NMR and IR spectroscopy, elemental analysis and in some cases by MS and X-ray diffraction analysis. In vitro studies indicate that the quinazoline fragments, after conjugation to the cyano group (L1, L2) or to the pyrazolyl containing chelator (L5H), as well as the corresponding Re complexes (7, 8, 10) inhibit significantly the EGFR autophosphorylation and also inhibit A431 cell growth. These two effects were also found for the pyridine-containing chelator (L6H) and corresponding Re complex (11), although to a lesser extent. 相似文献
92.
Hatziantoniou S Nezis IP Margaritis LH Demetzos C 《Micron (Oxford, England : 1993)》2007,38(8):777-781
Transmission electron microscopy was used to visualize the liposomes prepared from total lipids extracted from mouse, human and porcine skin and stratum corneum. The total lipid composition was monitored by high precision thin layer chromatography coupled with a flame identification detector (HPTLC/FID, Iatroscan) and the fatty acid content of the samples was monitored by gas chromatography. The liposomes were prepared by the thin lipid film hydration method and they were visualized by transmission electron microscopy after negative staining using uranyl acetate. The structure of the vesicular structures present in the formulations largely depended on the lipid composition of the samples. The liposomes with high ceramide content were drop like vesicles with sharp tips, whereas the presence of excessive phospholipid content lead to bag like liposomes with two hemispheres divided by a membrane. Finally, the tendency of triacylglycerides to accumulate in the lipophylic region of the lipid bilayer, forms membranes with uneven thickness, resulting in structures with undulated membranes. A degree of fusion depending on the phospholipid content was also observed. 相似文献
93.
The use of continuous-scan and step-scan Fourier transform infrared (FT-IR) spectroscopic techniques to study the dynamics of the response of polymer films and liquid crystals to external perturbations is described here. The first application of dynamic stepscan FT-IR deals with the response of various polymer films to sinusoidally modulated tensile strain. In these experiments, a small amplitude sinusoidal stress is applied to a polymeric film and the transition dipole responses are monitored as a phase lag with respect to the external perturbation. The degree of deformation is small enough to cause only linear reversible responses to the sample. The main advantage of the technique is that it can provide valuable information at the molecular level that can be used to interpret the macroscopic properties of the polymeric material under investigation. Results for heterogeneous polymers include semicrystalline high density/low density polyethylene blends and the micro-phase separated copolymer Kratonr̀ are presented. In addition, continuous-scan stroboscopic FT-IR was used to explore the submolecular (functional group) contributions to the reorientation dynamics of the liquid crystal director in response to pulsed (DC) electric fields. For the nematic liquid crystal molecules, 4-pentyl-4'-cyanobiphenyl (5CB) and 4-pentyl-4'-cyanophenylcyclohexane (5PCH), the individual response of the rigid and floppy parts was examined. 相似文献
94.
Carol B. Gell William W. Graessley Vasilis Efstratiadis Marinos Pitsikalis Nikos Hadjichristidis 《Journal of Polymer Science.Polymer Physics》1997,35(12):1943-1954
The crossover from linear to branched polymer dynamics in highly entangled melts was investigated with a series of asymmetric three-arm stars of poly(ethylene-alt-propylene). Two arms of equal length formed a linear backbone, kept constant through the series, while branches of various length were appended as the third arm. The materials were made by carbanionic polymerization of isoprene and the judicious application of chlorosilane linking chemistry. Subsequent saturation of the polymeric double bonds with deuterium and hydrogen, followed by fractionation, led to a set of structurally matched, nearly monodisperse pairs of deuterium-labeled and fully hydrogenous samples. Dynamic moduli were measured over wide ranges of frequency and temperature. With increasing branch length, the resulting master curves evolve smoothly, but with surprising rapidity, from the relatively narrow terminal spectrum of linear polymers to the much broader spectrum of symmetric stars. The viscosity ηo increases rapidly with branch length, and the diffusion coefficient D, obtained by forward recoil spectrometry, decreases even more rapidly. The product ηoD, however, distinguishes the transition from linear to branched polymer dynamics most clearly: for a backbone with about 38 entanglements, the crossover is already approaching completion for a single mid-backbone branch with only about three entanglements. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1943–1954, 1997 相似文献
95.
Thomas L. Theis Bhavik R. Bakshi Delcie Durham Vasilis M. Fthenakis Timothy G. Gutowski Jacqueline A. Isaacs Thomas Seager Mark R. Wiesner 《固体物理学:研究快报》2012,6(2):98-98
The name of a further author and contributor to this work, Roland Clift , has been added to the author list of the article in agreement with all co‐authors. It had been inadvertently omitted from the original version of the paper (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
96.
Thin coatings technology demands that characterization tools are readily available to distinguish between the composition and physical state of the coated layers versus the substrate. In principle, infrared photoacoustic spectroscopy (PAS) possesses all the appropriate features to become a mainstream technique for these types of characterizations. These features include the ability to characterize coatings of a variety of thickness (monolayers to tens of microns) and the fact that the technique requires virtually no sample preparation. One category of such samples involves systems having few micron thin layered structures coated on relatively thick polyester substrates. The phase delay of the photoacoustic signal can be used in conjunction with the knowledge of the thermal properties of the coated fluids in the calculation of the relative as well as the absolute depths of these multi-layered coatings. The phase delay is calculated at wavelengths that are characteristic of the various components of the different layers in the system. The technique is applied to the characterization of a coated system having a submicron layer as the top layer. Step-scan FT-IR photoacoustic data are presented that prove the ability of the technique to successfully isolate the infrared signature of the top layer from the infrared spectrum of the bulk material, proving the sub-micron resolution capability of the method. In addition, results will be shown that underline the fact that the most serious problem in PAS is saturation at high absorptivities. 相似文献
97.
Min Wang Vasilis Nikolaou Anna Loiudice Ian D. Sharp Antoni Llobet Raffaella Buonsanti 《Chemical science》2022,13(43):12673
Copper-based tandem schemes have emerged as promising strategies to promote the formation of multi-carbon products in the electrocatalytic CO2 reduction reaction. In such approaches, the CO-generating component of the tandem catalyst increases the local concentration of CO and thereby enhances the intrinsic carbon–carbon (C–C) coupling on copper. However, the optimal characteristics of the CO-generating catalyst for maximizing the C2 production are currently unknown. In this work, we developed tunable tandem catalysts comprising iron porphyrin (Fe-Por), as the CO-generating component, and Cu nanocubes (Cucub) to understand how the turnover frequency for CO (TOFCO) of the molecular catalysts impacts the C–C coupling on the Cu surface. First, we tuned the TOFCO of the Fe-Por by varying the number of orbitals involved in the π-system. Then, we coupled these molecular catalysts with the Cucub and assessed the current densities and faradaic efficiencies. We discovered that all of the designed Fe-Por boost ethylene production. The most efficient Cucub/Fe-Por tandem catalyst was the one including the Fe-Por with the highest TOFCO and exhibited a nearly 22-fold increase in the ethylene selectivity and 100 mV positive shift of the onset potential with respect to the pristine Cucub. These results reveal that coupling the TOFCO tunability of molecular catalysts with copper nanocatalysts opens up new possibilities towards the development of Cu-based catalysts with enhanced selectivity for multi-carbon product generation at low overpotential.Coupling the tunability of molecular catalysts and copper nanocatalysts opens up new possibilities towards the development of Cu-based catalysts with enhanced selectivity for multi-carbon product generation at low overpotential. 相似文献
98.
Maike Lettow Kim Greis Eike Mucha Tyler R. Lambeth Murat Yaman Vasilis Kontodimas Christian Manz Waldemar Hoffmann Gerard Meijer Ryan R. Julian Gert von Helden Mateusz Marianski Kevin Pagel 《Angewandte Chemie (International ed. in English)》2023,62(24):e202302883
Fucose is a signaling carbohydrate that is attached at the end of glycan processing. It is involved in a range of processes, such as the selectin-dependent leukocyte adhesion or pathogen-receptor interactions. Mass-spectrometric techniques, which are commonly used to determine the structure of glycans, frequently show fucose-containing chimeric fragments that obfuscate the analysis. The rearrangement leading to these fragments—often referred to as fucose migration—has been known for more than 25 years, but the chemical identity of the rearrangement product remains unclear. In this work, we combine ion-mobility spectrometry, radical-directed dissociation mass spectrometry, cryogenic IR spectroscopy of ions, and density-functional theory calculations to deduce the product of the rearrangement in the model trisaccharides Lewis x and blood group H2. The structural search yields the fucose moiety attached to the galactose with an α(1→6) glycosidic bond as the most likely product. 相似文献
99.
John A. Mikroyannidis Vasilis P. Barberis Věra Cimrová 《Journal of polymer science. Part A, Polymer chemistry》2007,45(6):1016-1027
A novel conjugated poly[(fluorene‐2,7‐vinylene)‐alt‐(1,4‐phenylenevinylene)] derivative 2 with quaternizable tertiary amino groups was synthesized by Heck coupling of a substituted 2,7‐dibromofluorene and 1,4‐dialkoxy‐2,5‐divinylbenzene. The corresponding quaternary ammonium cationic polyelectrolyte 3 was obtained by the treatment of 2 with bromoethane. Both polymers were soluble in common organic solvents, like tetrahydrofuran, chloroform, and dichloromethane. Polymer 3 showed a limited solubility in alcohols and was insoluble in water. Photophysical and electrochemical properties of the resulting polymers were fully investigated. An intensive green photoluminescence (PL) with maxima at 550 and 545 nm was observed from thin films of 2 and 3 polymers, respectively, red‐shifted compared with the PL emission spectra measured in the solution. The electrochemical band gaps were 2.38–2.45 eV. Single‐layer and double‐layer (with poly[3,4‐(ethylenedioxy)thiophene]/poly (styrenesulfonate) (PEDOT:PSS)) light‐emitting devices (LEDs) with ITO and Al electrodes were prepared and studied. They emitted a green light and their electroluminescence (EL) spectra were similar to those of PL thin films. The external EL efficiency was determined to be 0.43 and 0.32% for ITO/PEDOT:PSS/ 2 /Al and ITO/PEDOT:PSS/ 3 /Al LEDs, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1016–1027, 2007 相似文献
100.
The scientific and commercial interest for polymer aluminium silicate clay nanocomposites has risen dramatically over the last decades, whereas the monitoring of the extent of intercalation and exfoliation using an efficient, fast and convenient method remains an issue. For this purpose, infrared spectroscopy constitutes a very promising characterization technique to fulfill this role. Few studies have already been conducted towards this direction, however no direct correlation between the intercalation/exfoliation and the SiO stretching vibrations has been reported so far. In most cases multiple peaks are used for the fitting of the spectra without any direct report on their origin. We report for the first time in the present study the distinct vibrational species that are attributed to the intercalated/exfoliated structures and are necessary for the fitting of the spectra in the SiO stretching vibration region. Moreover, we also report that the intercalation/exfoliation process gives rise to two new peaks at around 1085 and 1040 cm−1 whose relative intensities to the main SiO stretching peaks at 1070 and 1050 cm−1 provide insight on the progress of intercalation/exfoliation in polymer clay nanocomposites. 相似文献