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61.
Kredel S Nienhaus K Oswald F Wolff M Ivanchenko S Cymer F Jeromin A Michel FJ Spindler KD Heilker R Nienhaus GU Wiedenmann J 《Chemistry & biology》2008,15(3):224-233
Fluorescent proteins (FPs) emitting in the far-red region of the spectrum are highly advantageous for whole-body imaging applications because scattering and absorption of long-wavelength light is markedly reduced in tissue. We characterized variants of the red fluorescent protein eqFP611 with bright fluorescence emission shifted up to 639 nm. The additional red shift is caused by a trans-cis isomerization of the chromophore. The equilibrium between the trans and cis conformations is strongly influenced by amino acid residues 143 and 158. Pseudo monomeric tags were obtained by further genetic engineering. For the red chromophores of eqFP611 variants, molar extinction coefficients of up to approximately 150,000 were determined by an approach that is not affected by the presence of molecules with nonfunctional red chromophores. The bright fluorescence makes the red-shifted eqFP611 variants promising lead structures for the development of near-infrared fluorescent markers. The red fluorescent proteins performed well in cell biological applications, including two-photon imaging. 相似文献
62.
Mangrove trees, which develop along tropical coasts, are known to use saline water uptake. In French Guiana, the high salinity condition is the result of seawater evaporation on mud banks formed from the Amazon sediment flumes. In the back mangrove a few kilometres inland, groundwater, soil water and the xylem sap uptake in the trees remain highly salty, and only very tolerant plants like Avicennia germinans can flourish, whereas the less salt-tolerant Rhizophora mangle is more difficult to find. Curiously, the same Avicennia trees propagate on the seafront. However, stable isotope ratio mass spectrometry (IRMS) measurements and ion analysis (high-performance liquid chromatography (HPLC) and inductively coupled plasma atomic emission (ICP-AES) spectroscopy reveal that the origin of the water in the back mangrove is not seawater. It is freshwater percolating into the sand bars from the inland marshes and rainwater during the wet season that redissolves a marine evaporite and gives a saline groundwater. The absence of barren saltine areas ('tanne') in French Guiana could be explained by this freshwater inflow, the aquifer being no longer linked with the ocean. Copyright (c) 2008 John Wiley & Sons, Ltd. 相似文献
63.
Dr. Ernesto Scoppola Dr. Erik B. Watkins Dr. Richard A. Campbell Dr. Oleg Konovalov Dr. Luc Girard Prof. Jean‐Francois Dufrêche Dr. Geoffroy Ferru Dr. Giovanna Fragneto Dr. Olivier Diat 《Angewandte Chemie (International ed. in English)》2016,55(32):9326-9330
Knowledge of the (supra)molecular structure of an interface that contains amphiphilic ligand molecules is necessary for a full understanding of ion transfer during solvent extraction. Even if molecular dynamics already yield some insight in the molecular configurations in solution, hardly any experimental data giving access to distributions of both extractant molecules and ions at the liquid–liquid interface exist. Here, the combined application of X‐ray and neutron reflectivity measurements represents a key milestone in the deduction of the interfacial structure and potential with respect to two different lipophilic ligands. Indeed, we show for the first time that hard trivalent cations can be repelled or attracted by the extractant‐enriched interface according to the nature of the ligand. 相似文献
64.
Fadil Iyikanat Prof. Dr. Ramazan T. Senger Prof. Dr. Francois M. Peeters Prof. Dr. Hasan Sahin 《Chemphyschem》2016,17(23):3985-3991
By using density functional theory and non‐equilibrium Green′s function‐based methods, we investigated the electronic and transport properties of a TiS3 monolayer p–n junction. We constructed a lateral p–n junction on a TiS3 monolayer using Li and F adatoms. An applied bias voltage caused significant variability in the electronic and transport properties of the TiS3 p–n junction. In addition, the spin‐dependent current–voltage characteristics of the constructed TiS3 p–n junction were analyzed. Important device characteristics were found, such as negative differential resistance and rectifying diode behaviors for spin‐polarized currents in the TiS3 p–n junction. These prominent conduction properties of the TiS3 p–n junction offer remarkable opportunities for the design of nanoelectronic devices based on a recently synthesized single‐layered material. 相似文献
65.
Hantash J Bartlett A Oldfield P Dénès G O'Rielly R David F 《Analytical and bioanalytical chemistry》2007,387(1):351-357
A flow-injection biosensor-like system based on a nonenzymatic approach has been developed to determine the carbamate pesticide
carbaryl in complex biological samples without lengthy and expensive extraction steps. Molecularly imprinted polymeric beads
were used to immobilize carbaryl from biological samples. pH variation permitted the elution of carbaryl from the binding
cavity to the flow cell. A pH electrode was used to detect changes in the charge of carbaryl in the sample solution resulting
from the protonation and deprotonation of the molecule over different pH ranges. At pH 2.0, the secondary amine group is protonated,
giving a (+1) charge to the carbaryl molecule. At pH 8.0, the ionized carbaryl loses a proton to become neutral, changing
the local pH of the flow cell. The pH change at the flow cell generated by the deprotonation of carbaryl ion in alkaline medium
was used to determine the carbaryl concentration. Parameters influencing the performance of the system were optimized for
use in the detection procedure. The validated biosensor-like system had a carbaryl detection limit of 10.0 μg/mL and a response
that was linear (r
2 > 0.98) over the concentration range of 10.0–00 μg/mL. 相似文献
66.
67.
Chitosan loaded with silver nanoparticles,CS‐AgNPs,using thymus syriacus,wild mint,and rosemary essential oil extracts as reducing and capping agents 下载免费PDF全文
Fadi AL‐Shnani Thanaa Al‐Haddad Francois Karabet Abdul Wahab Allaf 《Journal of Physical Organic Chemistry》2017,30(11)
The present study describes the green method for the preparation of chitosan loaded with silver nanoparticles (CS‐AgNPs) in the presence of 3 different extracted essential oils. The essential oils play dual roles as reductant and capping agents. The reducing power and DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) assay for the 3 essential oils—Thymus syriacus (T), wild mint (M), and rosemary (R)—have been reported. The preparation of CS‐AgNPs was performed by 2 steps. The 3 previously extracted essential oils have been used as reducing and capping agent in the first step, while in the second step, silver nanoparticles were integrated in chitosan. The integration of AgNPs in the structure of chitosan was confirmed by ultraviolet‐visible, Fourier transform infrared spectroscopy, scanning electron microscopy techniques, and energy dispersive X‐ray. Surface plasmon resonance confirmed the formation of CS‐AgNPs with maximum absorbance at λmax between 405 ‐ 410 and 410 ‐ 430 nm for colloidal and films of CS‐AgNPs, respectively. The intensity of bands at 3408 cm?1 in the fourier transform infrared spectroscopy measurements was decreased substantially and shifted slightly to lower frequency (?υ = 43 cm?1). Scanning electron microscopy shows a spherical morphology of AgNPs with size of 62 nm for both colloidal and film samples, and energy dispersive X‐ray analysis shows peaks confirming AgNPs formation. 相似文献
68.
Valerio Scagnoli Claudio Mazzoli Carsten Detlefs Pascal Bernard Andrea Fondacaro Luigi Paolasini Federica Fabrizi Francois De Bergevin 《Journal of synchrotron radiation》2009,16(6):778-787
An in‐vacuum double‐phase‐plate diffractometer for performing polarization scans combined with resonant X‐ray diffraction experiments is presented. The use of two phase plates enables the correction of some of the aberration effects owing to the divergence of the beam and its energy spread. A higher rate of rotated polarization is thus obtained in comparison with a system with only a single retarder. Consequently, thinner phase plates can be used to obtain the required rotated polarization rate. These results are particularly interesting for applications at low energy (e.g. 4 keV) where the absorption owing to the phase plate(s) plays a key role in the feasibility of these experiments. Measurements by means of polarization scans at the uranium M4 edge on UO2 enable the contributions of the magnetic and quadrupole ordering in the material to be disentangled. 相似文献
69.
Recently, surface modifications on a commercial Ni/γ-Al2O3 catalyst during the production of methane from synthesis gas were investigated by quasi insitu X-ray photoelectron spectroscopy (XPS) [I. Czekaj, F. Loviat, F. Raimondi, J. Wambach, S. Biollaz, A. Wokaun, Appl. Catal. A: Gen. 329 (2007) 68]. The conclusion was that the reactivity and the observed reaction mechanisms on the different Ni particles are influenced directly by both the size and the composition of the particles on the γ-Al2O3 support.In this investigation, Ni deposition and cluster growth on model catalyst samples (10 nm thick, polycrystalline γ-Al2O3 on Si(100)) were investigated by XPS. Several steps in the binding energy during Ni deposition indicate changes in the cluster growth. The molecular structure of the catalyst was investigated using Density Functional Theory calculations (StoBe) with a cluster model and non-local functional (RPBE) approach. An Al15O40H35 cluster was selected to represent the γ-Al2O3(100) surface. Ni clusters of different size were cut from a Ni(100) surface and deposited on the Al15O40H35 cluster in order to validate the deposition model determined by XPS. 相似文献
70.
McMahon G Saint-Cyr HF Lechene C Unkefer CJ 《Journal of the American Society for Mass Spectrometry》2006,17(8):1181-1187
We have studied the mechanism of formation CN- secondary ions under Cs+ primary ion bombardment. We have synthesized 13C and 15N labeled polyglycine samples with the distance between the two labels and the local atomic environment of the 13C label systematically varied. We have measured four masses in parallel: 12C, 13C, and two of 12C14N, 13C14N, 12C15N, and 13C15N. We have calculated the 13C/12C isotope ratio, and the different combinations of the CN isotope ratios (27CN/26CN, 28CN/27CN, and 28CN/26CN). We have measured a high 13C15N- secondary ion current from the 13C and 15N labeled polyglycines, even when the 13C and 15N labels are separated. By comparing the magnitude of the varied combinations of isotope ratios among the samples with different labeling positions, we conclude the following: CN- formation is in large fraction due to recombination of C and N; the CO double bond decreases the extent of CN- formation compared to the case where carbon is singly bonded to two hydrogen atoms; and double-labeling with 13C and 15N allows us to detect with high sensitivity the molecular ion 13C15N-. 相似文献