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11.
Self-assembled monolayers of alpha-helical peptides on a gold surface were employed as model systems for the investigation of mediated electron transfer. The peptides contained 14, 15, 16, and 17 amino acid residues. The measurements of electron transmission through single molecules of helical peptides were performed using scanning tunneling spectroscopy (STS). The molecules were trapped between the gold tip and the substrate. Electrical contact between the molecule and the gold probe was achieved by the use of peptides containing thiol groups present at each end of the helix. The conductance behavior of the peptides was examined as a function of tip-substrate distance at fixed bias voltage. Measurements performed with peptides containing different numbers of amino acid residues indicate that the distance dependence of electron transmission through an alpha-helix is weaker than that through simple n-alkyl bridges. 相似文献
12.
Polypropylene and poly(ethylene‐co‐1‐octene) effective synthesis with diamine‐bis(phenolate) complexes: Effect of complex structure on catalyst activity and product microstructure 下载免费PDF全文
Marzena Białek Elwira Bisz 《Journal of polymer science. Part A, Polymer chemistry》2017,55(15):2467-2476
A series of group 4 metal complexes bearing amine‐bis(phenolate) ligands with the amino side‐arm donor: (μ‐O)[Me2N(CH2)2N(CH2‐2‐O‐3,5‐tBu2‐C6H2)2ZrCl]2 ( 1a ), R2N(CH2)2N(CH2‐2‐O‐3‐R1‐5‐R2‐C6H2)2TiCl2 (R = Me, R1, R2 = tBu ( 2a ), R = iPr, R1, R2 = tBu ( 2b ), R = iPr, R1 = tBu, R2 = OMe ( 2c )), and Me2N(CH2)2N(CH2‐2‐O‐3,5‐tBu2‐C6H2)(CH2‐2‐O‐C6H4)TiCl2 ( 2d ) are used in ethylene and propylene homopolymerization, and ethylene/1‐octene copolymerization. All complexes, upon their activation with Al(iBu)3/Ph3CB(C6F5)4, exhibit reasonable catalytic activity for ethylene homo‐ and copolymerization giving linear polyethylene with high to ultra‐high molecular weight (600·× 103–3600·× 103 g/mol). The activity of 1a /Al(iBu)3/Ph3CB(C6F5)4 shows a positive comonomer effect, leading to over 400% increase of the polymer yield, while the addition of 1‐octene causes a slight reduction of the activity of the complexes 2a‐2d . The complexes with the NMe2 donor group ( 2a , 2d , 1a ) display a high ability to incorporate a comonomer (up to 9–22 mol%), and the use of a bulkier donor group, N(iPr)2 ( 2b , 2c ), results in a lower 1‐octene incorporation. All the produced copolymers reveal a broad chemical composition distribution. In addition, the investigated complexes polymerized propylene with the moderate ( 1a , 2a ) to low ( 2b‐2d ) activity, giving polymers with different microstructures, from purely atactic to isotactically enriched (mmmm = 28%). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2467–2476 相似文献
13.
Elwira Chrobak Andrzej Maślankiewicz Magdalena Chyćko Leszek Skrzypek Małgorzata Szmielew Maria J. Maślankiewicz 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):1208-1225
Abstract Treatment of 1,4-dithiino[2,3-c:5,6-c′]diquinoline (a thioquinanthrene) (1a) with an excess of nitrating mixture (0 °C, 14 days) led to a mixture of mono- and dinitrothioquinanthrene 7-oxides 2b–e and 2f–h. This mixture was: (i) reduced to a mixture of mono- and dinitrothioquinanthrenes 1b– e, or (ii) oxidatively chlorinated with a gaseous chlorine/80% acetic acid/hydrochloric acid system to a mixture of 4-chloro-3-chlorosulfonylquinoline 3a and its 5- and 8-nitroderivatives 3b and 3d. Sulfochlorides 3a– d were independently synthesized from 3,4′-diquinolinyl sulfides 4 and converted to the respective 4-dimethylamino-3-quinoline-N,N-dimethylsulfonamides 9a–d. 相似文献
14.
This paper presents results of the photoacoustic (PA) spectral studies, of a series of silicon samples with differently prepared
surfaces, in two PA experimental configurations, so-called, absorption and transmission ones. The PA amplitude spectra of
the samples indicated existence of the damaged surface layers. In the paper, the two layer mathematical models of a sample
with a damaged surface layer that were used for numerical interpretation of the amplitude PA spectra of the investigated samples,
are presented and discussed. 相似文献
15.
This paper presents step by step the procedure of determination of the quantum efficiency of luminescence of Mn2+ ions in the Zn1−x−yBexMnySe crystals. The method is based on the photoacoustic spectroscopy approach. In the paper, the experimental spectra of absorbance,
transmission, absorption and photoacoustic spectra of the samples are presented and analyzed from the point of view of the
possibility of determination of the quantum efficiency of Mn2+ ion luminescence at room temperature. It was determined experimentally that in the investigated crystals the quantum efficiency
of luminescence in the Mn2+ ions is about 35%, 40%, 32% for the absorption peaks at 430 nm, 470 nm, and 510 nm, respectively, for Zn0.75Be0.2Mn0.05Se crystal. 相似文献
16.
Grzegorz Kalisz Barbara Gieroba Olga Chrobak Magdalena Suchora Agata L. Starosta Anna Sroka-Bartnicka 《Molecules (Basel, Switzerland)》2021,26(5)
Fourier Transform Infrared (FT-IR) spectroscopy and imaging combined with hierarchical cluster analysis (HCA) was applied to analyse biochemical properties of Early Middle Ages hemp (Cannabis sativa L.) bast fibres collected from lake bottom sediment of lake Słone. The examined plant macrofossil material constitutes residues of the hemp retting process that took place in the 7th–8th century. By comparison of three samples: untreated isolated bast fibres, and fibres incubated overnight at 4 and 37 °C, we were able to mimic the retting conditions. Using FT-IR qualitative and semi-quantitative assessment of the primary polysaccharides content, total protein content, and their spatial distribution was performed within the hemp fibres. The concentration of cellulose remained vastly unchanged, while the concentration of lignin and pectin was the highest in the untreated sample. The spatial distributions of compounds were heterogeneous in the untreated and 4 °C-incubated samples, and homogenous in the specimen processed at 37 °C. Interestingly, a higher amide content was detected in the latter sample indicating the highest degree of enzymatic degradation. In this study, we show that the spectroscopic methods allow for a non-destructive evaluation of biochemical composition of plant fibres without preparation, which can be an appropriate approach for studying ancient plant remains. 相似文献
17.
Kadela-Tomanek Monika Bober Katarzyna Bębenek Ewa Chrobak Elwira Boryczka Stanisław 《平面色谱法杂志一现代薄层色谱法》2017,30(3):219-224
JPC – Journal of Planar Chromatography – Modern TLC - Lipophilicity is a very important property while designing new drugs. Its influence on the pharmacological responses of compounds... 相似文献
18.
The work concerns influence of rare earth elements on crystallization of Fe82Nb2B14RE2 (RE = Y, Gd, Tb, and Dy) group of amorphous alloys. The samples were obtained by typical melt spinning technique. The crystallization studies were carried out with the use of (i) differential scanning calorimetry (DSC) in the temperature range from 300 K to 850 K with different heating rates and (ii) standard magnetic balance (Faraday type). The crystalline structure before and after the first stage of crystallization were checked by XRD and HRTEM techniques. The measurements allow the determining crystallization temperatures, activation energies of crystallization, average size of nanograins formed during crystallization and the Curie temperatures. In the paper all the obtained results are widely discussed in the context of different rare earth alloying additions. 相似文献
19.
Urszula E. Wawrzyniak Mateusz Woźny Jarosław Kowalski Sławomir Domagała Elwira Maicka Renata Bilewicz Prof. Krzysztof Woźniak Prof. Bohdan Korybut‐Daszkiewicz Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(1):149-157
New dithiolated derivatives of neutral CuII and NiII tetraazamacrocyclic complexes have been synthesized and characterized by spectroscopic and diffractional methods. These rod‐shaped molecules were assembled in monocomponent and mixed monolayers on gold electrodes. In the mixed monolayers, the active molecules were embedded in a hexanethiol matrix. The dithiolated complexes are oriented perpendicularly to the electrode, and reveal faster kinetics of electron transfer than those assembled in a single‐component monolayer. They appear as protrusions, which are easily addressed by using the STM method. In the presence of a suitable electron acceptor in the solution, the donor properties of the anchored Cu complex were weakened, which revealed donor–acceptor interactions with the monolayer. The peak position in the voltammogram indicates a stronger interaction of the solution‐based acceptor with the reduced CuII form than with the CuIII complex. This suggests the possibility of switching the association on or off by applying an appropriate potential. 相似文献
20.
A new electrochemical method for the determination of trace water in methanol has been developed. This method is based on the effect, that a minor change in the water content affects the value of conductivity measured for dissolved in the solutions electrolyte. The conductivity measurements were performed for four inorganic salts, i.e. NaCl, KCl, RbCl, and CsCl in solutions with different amounts of water traces in methanol and the calibration curves for three of them were determined. With the exception of cesium chloride the high values of correlation coefficients for the regression lines as well as low limits of detection were achieved in all cases which indicates that this method is a useful tool for the determination of the trace amounts of water in methanol. 相似文献