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221.
Patricia Lpez‐García Aline D. de Araujo Ana E. Bergues‐Pupo Isabell Tunn David P. Fairlie Kerstin G. Blank 《Angewandte Chemie (International ed. in English)》2021,60(1):232-236
Coiled coils (CCs) are powerful supramolecular building blocks for biomimetic materials, increasingly used for their mechanical properties. Here, we introduce helix‐inducing macrocyclic constraints, so‐called staples, to tune thermodynamic and mechanical stability of CCs. We show that thermodynamic stabilization of CCs against helix uncoiling primarily depends on the number of staples, whereas staple positioning controls CC mechanical stability. Inserting a covalent lactam staple at one key force application point significantly increases the barrier to force‐induced CC dissociation and reduces structural deformity. A reversible His‐Ni2+‐His metal staple also increases CC stability, but ruptures upon mechanical loading to allow helix uncoiling. Staple type, position and number are key design parameters in using helical macrocyclic templates for fine‐tuning CC properties in emerging biomaterials. 相似文献
222.
Ohne Zusammenfassung 相似文献
223.
V. D. Blank A. A. Nuzhdin V. M. Prokhorov R. Kh. Bagramov 《Physics of the Solid State》1998,40(7):1261-1263
Measurements of the specific heat and elastic wave velocities for a C60 fullerene sample treated at high pressure and temperature are used to estimate the Debye temperature and the function ΔC=C
p−C
v, and also to calculate the thermal expansion work in the ideal approximation. Similar calculations were made for graphite,
diamond, silicon, germanium, and various refractory metals. The results were used to draw qualitative conclusions on the structural
stability of a new material obtained from fullerene C60 which possesses extremely high hardness.
Fiz. Tverd. Tela (St. Petersburg) 40, 1387–1389 (July 1998) 相似文献
224.
Enantioselective or diastereoselective intramolecular cyclization of functionalized secondary phosphines or their borane adducts catalyzed by chiral Pd(diphosphine) complexes gave P-stereogenic benzophospholanes in up to 70% ee. These results provide a new method for the synthesis of chiral phospholanes, which are valuable ligands in asymmetric catalysis. [reaction: see text] 相似文献
225.
The surfaces of constant Gaussian curvature bearing conjugate networks of conic lines are found.Translated from Ukrainskií Geometricheskií Sbornik, Issue 29, 1986, pp. 3–5. 相似文献
226.
Electron Spin Resonance Imaging Probes and a Sample Holder for Thin and Long One-Dimensional Samples
Most electron spin resonance (ESR) experiments involve the use of samples that can be easily placed in millimeter-size tubes and measured efficiently in conventional resonators. However, in some cases, the samples must remain intact, due to which conventional commercial resonators may not be suitable to measure them. Here, we describe a set of three resonators, which can be combined and incorporated as part of a 1-D continuous wave ESR imaging probe to measure and image very thin (~50–500 μm) and very long (~10–30 mm) objects. The dielectric resonators we employ make it possible to greatly enhance spin sensitivity per unit of length––compared to the use of a rectangular ESR cavity, at ~9.3 GHz. In addition, a special sample holder was developed to facilitate the handling and measurement of such thin and long delicate objects, which in our case are the Arabidopsis roots. A detailed design of the resonators, imaging probe, and the sample holder is provided, along with experimental results for the resonator properties, its spin sensitivity, and imaging capability. 相似文献
227.
Dr. Nir Dayan Dr. Yaron Artzi Moamen Jbara Dr. David Cristea Prof. Aharon Blank 《Chemphyschem》2023,24(7):e202200624
Nuclear magnetic resonance (NMR) spectroscopy provides atomic-level molecular structural information. However, in molecules containing unpaired electron spins, NMR signals are difficult to measure directly. In such cases, data is obtained using the electron-nuclear double resonance (ENDOR) method, where nuclei are detected through their interaction with nearby unpaired electron spins. Unfortunately, electron spins spread the ENDOR signals, which challenges current acquisition techniques, often resulting in low spectral resolution that provides limited structural details. Here, we show that by using miniature microwave resonators to detect a small number of electron spins, integrated with miniature NMR coils, one can excite and detect a wide bandwidth of ENDOR data in a single pulse. This facilitates the measurement of ENDOR spectra with narrow lines spread over a large frequency range at much better spectral resolution than conventional approaches, which helps reveal details of the paramagnetic molecules’ chemical structure that were not accessible before. 相似文献
228.
Schaut A De Saeger S Sergent T Schneider YJ Larondelle Y Pussemier L Blank R Van Peteghem C 《Biomedical chromatography : BMC》2008,22(9):1013-1020
Liquid chromatographic methods were used for the detection of ochratoxin A (OTA) and its metabolites ochratoxin alpha (OTalpha), 10-hydroxy OTA (10-OHOTA), 4R-hydroxy OTA (4R-OHOTA) and the ethyl ester of OTA (OTC) in in vitro samples, obtained with Caco-2 cell culture experiments and in in vivo urine samples from sheep. A high-performance liquid chromatography method with fluorescence detection (HPLC-FLD) and a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method were developed and validated for the detection of OTA and its metabolites OTalpha, 10-OHOTA, 4R-OHOTA and OTC, which was used as internal standard. The LOD/LOQ values for OTalpha, 4R-OHOTA and OTA were 0.63/2.11, 0.99/3.31 and 0.84/2.81 microg/L, respectively, for the HPLC-FLD method and 0.98/3.28, 1.11/3.72 and 0.88/2.96 microg/L, respectively for the LC-MS/MS method. Within-day and between-day precision were both <12% for the HPLC-FLD method, and <10% for the LC-MS/MS method. The recovery of OTA and its metabolites ranged between 71 and 111% for the HPLC-FLD method and between 79 and 110 % for the LC-MS/MS method. In the first experiment only OTA was added to the Caco-2 cells while in the second experiment 3-methylcholanthrene (3MC) was also present in the cell culture systems. Besides OTA, which was recovered in all the samples, an unknown compound was also observed in the second experiment. When 3MC was added, the results showed that the OTA concentration in the basolateral samples was decreased by 50%. The methods were also implemented for the analysis of urine samples of sheep, fed increasing amounts of OTA. With the HPLC-FLD method it could be concluded that the concentration of OTA and OTalpha increased according to ingested amounts of OTA, with OTalpha being the most abundant compound. The results obtained with the LC-MS/MS method confirmed these results. Copyright (c) 2008 John Wiley & Sons, Ltd. 相似文献
229.
Stawski TM Veldhuis SA Castricum HL Keim EG Eeckhaut G Bras W Blank DH ten Elshof JE 《Langmuir : the ACS journal of surfaces and colloids》2011,27(17):11081-11089
The structural evolution of sol-gel derived lead zirconate titanate (PZT) precursor films during and after physical drying was investigated by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), selected area electron diffraction (SAED), and time-resolved X-ray diffraction (XRD). Films were deposited from initial 0.3 mol/dm(3) precursor sols with varying hydrolysis ratios. Zr-rich grains of 1-10 nm size, embedded in a Pb-, Zr-, and Ti-containing amorphous matrix were found in as-dried films. The Zr-rich regions were crystalline at hydrolysis ratios [H(2)O]/[PZT] < 27.6, and amorphous at ratios > 100. X-ray diffraction analysis of PZT and zirconia sols revealed that the crystalline nanoparticles in both sols are identical and are probably composed of nanosized zirconium oxoacetate-like clusters. This study demonstrates that time-resolved X-ray diffraction combined with electron energy loss spectroscopy mapping is a powerful tool to monitor the nanoscale structural evolution of sol-gel derived thin films. 相似文献
230.
Silvana V. F. Gomes Alan D. C. Santos Valéria R. S. Moraes Lúcia R. R. Martins Monalisa D. Viana Arie F. Blank Edenir R. Pereira-Filho Quezia B. Cass Paulo C. L. Nogueira Péricles B. Alves 《Chromatographia》2010,72(3-4):275-280
A liquid chromatographic method with photodiode-array detection has been developed for differentiation of seven genotypes of Lippia gracilis Schauer, originated from Sergipe state (named 106 to 110) and from Bahia state (201 and 202), cultivated and collected in the rural campus of the Federal University of Sergipe. For a comparative analysis of the fingerprint chromatograms, chemometric tools were applied with exploratory methods. The genotypes were differentiated and their relationship with original place was established (Sergipe and Bahia states) by principal component analysis of the fingerprint chromatograms of both leaves and stem samples. 相似文献