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101.
Sandberg RL Paul A Raymondson DA Hädrich S Gaudiosi DM Holtsnider J Tobey RI Cohen O Murnane MM Kapteyn HC Song C Miao J Liu Y Salmassi F 《Physical review letters》2007,99(9):098103
We present the first experimental demonstration of lensless diffractive imaging using coherent soft x rays generated by a tabletop soft-x-ray source. A 29 nm high harmonic beam illuminates an object, and the subsequent diffraction is collected on an x-ray CCD camera. High dynamic range diffraction patterns are obtained by taking multiple exposures while blocking small-angle diffraction using beam blocks of varying size. These patterns reconstruct to images with 214 nm resolution. This work demonstrates a practical tabletop lensless microscope that promises to find applications in materials science, nanoscience, and biology. 相似文献
102.
We tested the hypothesis that partial volume effects due to poor in-plane resolution and/or low temporal resolution used in clinical dynamic contrast-enhanced magnetic resonance imaging results in erroneous diagnostic information based on inaccurate estimates of tumor contrast agent extravasation and tested whether reduced encoding techniques can correct for dynamic data volume averaging. Image spatial resolution was reduced from 469 x 469 microm2 to those reported below by selecting a subset of k-space data. We then compared the top five K(trans)/V(T) "hot spots" obtained from the original data set, 469 x 469-microm in-plane spatial resolution and an 18-s temporal resolution processed by fast Fourier transform (FFT), with values obtained from data sets having in-plane spatial resolutions of 938 x 938, 1875 x 1875 and 2500 x 2500 microm2 and a temporal resolution of 18 s, or data sets with temporal resolutions of 36, 54 and 72 and a spatial resolution of 469 x 469 microm2, and found them to statistically differ from the parent data sets. We then tested four different post processing methods for improving the spatial resolution without sacrificing temporal resolution: zero-filled FFT, keyhole, reduced-encoding imaging by generalized-series reconstruction (RIGR) and two-reference RIGR (TRIGR). The top five values of K(trans)/V(T) obtained from data sets, the in-plane spatial resolutions of which were improved to 469 x 469 microm2 by zero-filling FFT, Keyhole and RIGR, statistically differed from those obtained from the original 469 x 469 microm2 FFT parent image data set. Only the 938 x 938 and 1875 x 1875 microm2 data sets reconstructed to 469 x 469 microm2 with TRIGR reconstruction method yielded values of the top five K(trans)/V(T) hot spots statistically the same as the original parent data set, 469 x 469 microm2 in-plane spatial and 18-s temporal-resolution FFT. That is, partial volume effects from data sets of different in-plane spatial resolution resulted in statistically different values of the top five K(trans)/V(T) hot spots relative to a high spatial and temporal resolution data set, and TRIGR reconstruction of these low resolution data sets to high resolution images provided statistically similar values with a savings in temporal resolution of 2 to 4 times. 相似文献
103.
Pabla A. Barra Luis F. Barraza Verónica A. Jiménez José A. Gavin Joel B. Alderete 《Structural chemistry》2014,25(5):1443-1455
Fully atomistic molecular dynamics (MD) simulations and NMR spectroscopy were employed to get insights about the molecular details of drug-dendrimer supramolecular association phenomena, using piroxicam (PRX) and the third generation poly(amido amine) (PAMAM-G3) dendrimer as model systems. Theoretical results concerning the complex stoichiometry suggest that PRX forms drug-dendrimer complexes of the type 24:1 at pH 7.0. This result was validated with the experimental quantities obtained from aqueous solubility profiles, which led to an empiric stoichiometry of 23:1 for the PRX:PAMAM-G3 system. The predicted binding mode between PRX and PAMAM-G3 accounts for the preferred encapsulation of the drug inside dendrimer cavities, which is mainly driven by van der Waals and hydrogen bonding interactions, and to a lesser extent, for the external association of the guest through electrostatic contacts with the positively charged amino groups of PAMAM periphery. The binding mode obtained from MD simulations was confirmed with 2D-NOESY experiments, which evidence the preferred internal complexation of PRX with PAMAM-G3. The predominance of internal encapsulation over external contacts in the PRX:PAMAM-G3 system differs from the general behaviour expected for acidic anionic guests, for which external electrostatic interactions with the positively charged PAMAM surface have been postulated as the most relevant factor for drug association. 相似文献
104.
María José Heras‐Ojea Daniel Reta Mañeru Lidia Rosado Dr. Juan Rubio Zuazo Dr. German R. Castro Subrata Tewary Dr. Gopalan Rajaraman Dr. Guillem Aromí Dr. Erika Jiménez Dr. E. Carolina Sañudo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(33):10439-10445
The new diimine fluorescent ligand ACRI‐1 based on a central acridine yellow core is reported along with its coordination complex [Co2( ACRI‐1 )2] ( 1 ), a fluorescent weak ferromagnet. Due to the strong fluorescence of the acridine yellow fluorophore, it is not completely quenched when the ligand is coordinated to CoII. The magnetic properties of bulk complex 1 and its stability in solution have been studied. Complex 1 has been deposited on highly ordered pyrolitic graphite (HOGP) from solution. The thin films prepared have been characterized by AFM, time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS), grazing incidence X‐ray diffraction (GIXRD), X‐ray absorption spectroscopy (XAS), X‐ray magnetic circular dichroism (XMCD) and theoretical calculations. The data show that the complex is robust and remains intact on the surface of graphite. 相似文献
105.
Bixue Xu Luca Unione Dr. Joao Sardinha Shaoping Wu Prof. Mélanie Ethève‐Quelquejeu Prof. Amelia Pilar Rauter Prof. Yves Blériot Dr. Yongmin Zhang Dr. Sonsoles Martín‐Santamaría Dr. Dolores Díaz Prof. Jesus Jiménez‐Barbero Prof. Matthieu Sollogoub 《Angewandte Chemie (International ed. in English)》2014,53(36):9597-9602
Molecular mimicry is an essential part of the development of drugs and molecular probes. In the chemical glycobiology field, although many glycomimetics have been developed in the past years, it has been considered that many failures in their use are related to the lack of the anomeric effects in these analogues. Additionally, the origin of the anomeric effects is still the subject of virulent scientific debates. Herein, by combining chemical synthesis, NMR methods, and theoretical calculations, we show that it is possible to restore the anomeric effect for an acetal when replacing one of the oxygen atoms by a CF2 group. This result provides key findings in chemical sciences. On the one hand, it strongly suggests the key relevance of the stereoelectronic component of the anomeric effect. On the other hand, the CF2 analogue adopts the natural glycoside conformation, which might provide new avenues for sugar‐based drug design. 相似文献
106.
Dr. Iryna Antonyshyn Dipl.-Eng. Ana M. Barrios Jiménez Dr. Olga Sichevych Dr. Ulrich Burkhardt Dr. Igor Veremchuk Dr. Marcus Schmidt Dr. Alim Ormeci Dr. Ioannis Spanos Dr. Andrey Tarasov Dr. Detre Teschner Dr. Gerardo Algara-Siller Prof. Dr. Robert Schlögl Prof. Yuri Grin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16913-16919
107.
Juan-Ramón Jiménez Jana Glatz Amina Benchohra Geoffrey Gontard Lise-Marie Chamoreau Jean-François Meunier Azzedine Bousseksou Rodrigue Lescouëzec 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(21):8166-8170
A mixed-valence {MnII3MnIIIFeII2FeIII2} cyanide-bridged molecular cube hosting a caesium cation, Cs⊂{Mn4Fe4}, was synthesized and structurally characterized by X-ray diffraction. Cyclic-voltammetry measurements show that its electronic state can be switched between five different redox states, which results in a remarkable electrochromic effect. Magnetic measurements on fresh samples point to the occurrence of a spin-state change near room temperature, which could be ascribed to a metal-to-metal electron transfer converting the {FeII−CN−MnIII} pair into a {FeIII−CN−MnII} pair. This feature was only previously observed in the polymeric MnFe Prussian-blue analogues (PBAs). Moreover, this novel switchable molecule proved to be soluble and stable in organic solvents, paving the way for its integration into advanced materials. 相似文献
108.
Apoorva D. Srivastava Dr. Luca Unione Dr. Margreet A. Wolfert Dr. Pablo Valverde Dr. Ana Ardá Prof. Dr. Jesús Jiménez-Barbero Prof. Dr. Geert-Jan Boons 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(67):15605-15612
The parasitic worm, Schistosoma mansoni, expresses unusual fucosylated glycans in a stage-dependent manner that can be recognized by the human innate immune receptor DC-SIGN, thereby shaping host immune responses. We have developed a synthetic approach for mono- and bis-fucosylated LacdiNAc (LDN-F and LDN-DF, respectively), which are epitopes expressed on glycolipids and glycoproteins of S. mansoni. It is based on the use of monosaccharide building blocks having carefully selected amino-protecting groups, facilitating high yielding and stereoselective glycosylations. The molecular interaction between the synthetic glycans and DC-SIGN was studied by NMR and molecular modeling, which demonstrated that the α1,3-fucoside of LDN-F can coordinate with the Ca2+-ion of the canonical binding site of DC-SIGN allowing for additional interactions with the underlying LDN backbone. The 1,2-fucoside of LDN-DF can be complexed in a similar manner, however, in this binding mode GlcNAc and GalNAc of the LDN backbone are placed away from the protein surface resulting in a substantially lower binding affinity. Glycan microarray binding studies showed that the avidity and selectivity of binding is greatly enhanced when the glycans are presented multivalently, and in this format Lex and LDN-F gave strong responsiveness, whereas no binding was detected for LDN-DF. The data indicates that S. mansoni has developed a strategy to avoid detection by DC-SIGN in a stage-dependent manner by the addition of a fucoside to a number of its ligands. 相似文献
109.
Bismuth borate glasses containing phosphors and luminescent rare-earths are of interest for applications in light-emitting devices. Herein, the influence of CuO impurities on red-emitting Eu3+-doped bismuth borate glasses of the 25Bi2O3-15BaO-10Li2O-50B2O3 type was investigated by various spectroscopic methods. The glasses were prepared by the melt-quench technique and characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, UV/Vis optical absorption (OA), and photoluminescence (PL) spectroscopy including decay kinetics assessment. The XRD data confirmed the amorphous nature of the glasses whereas FT-IR spectra indicated the basic structural features of trigonal BO3 units and BO4 tetrahedra. The OA analysis showed that addition of CuO up to 0.5 mol% results in significant growth of the visible Cu2+ absorption band around 715 nm, with slight decrease in the optical band gap energies assessed through Tauc plots. A drastic PL quenching of Eu3+ ions emission was evidenced concurring with the detrimental effect of Cu2+. The assessment of the Eu3+ emission decay curves revealed significant lifetime decrease of the 5D0 emitting state with increasing CuO concentration. An analysis of quenching constants was finally performed comparing results from integrated PL data with the emission decay rates. It is argued that the bismuth borate glass system supports an effective Eu3+→Cu2+ energy transfer (more so than phosphates) in connection with a strong spectral overlap between Eu3+ emission and Cu2+ absorption. 相似文献
110.
以邻苯二甲醛柱前衍生,ODS(C_(18))柱分离,pH 6.0乙酸盐缓冲溶液与甲醇二元梯度洗脱,荧光检测,仅9min内分离测定了大鼠脑中5种氨基酸递质的含量。在1~10μmol·L~(-1)浓度范围内,氨基酸的峰面积与其浓度呈现良好的线性关系,相关系数在0.9978~0.9999之间。 相似文献