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71.
Light‐Driven Reversible Alignment Switching of Liquid Crystals Enabled by Azo Thiol Grafted Gold Nanoparticles 下载免费PDF全文
Dr. Chenming Xue Jie Xiang Hossein Nemati Dr. Hari Krishna Bisoyi Karla Gutierrez‐Cuevas Dr. Ling Wang Dr. Min Gao Shuang Zhou Prof. Deng‐ke Yang Prof. Oleg D. Lavrentovich Dr. Augustine Urbas Prof. Quan Li 《Chemphyschem》2015,16(9):1852-1856
Stimuli‐directed alignment control of liquid crystals (LCs) with desired molecular orientation is currently in the limelight for the development of smart functional materials and devices. Here, photoresponsive azo thiol (AzoSH) was grafted onto gold nanoparticles (GNPs). The resulting hybrid GNPs were able to homogeneously mix with a commercially available nematic LC host, as evidenced by Cryo‐TEM. Interestingly, the LC nanocomposites were found to undergo reversible alignment transition upon light irradiation as a consequence of the trans–cis photoisomerization of the azo groups on the GNP surface. LC molecules in either planar or bare glass cells were able to change their alignment to vertical upon UV irradiation, while the vertically aligned LC molecules returned to the planar or random orientation under visible irradiation. Neither the azo thiol molecules nor the unfunctionalized GNPs alone promoted the alignment of the LC molecules in the system upon light irradiation. The photoinduced vertical alignment without applied electric or magnetic field was very stable over time and with respect to temperature. Furthermore, an optically switchable device based on the photostimulated reversible alignment control of LCs was demonstrated. 相似文献
72.
We show that the r-dominated polynomials on p(2 p ) are integral on 1, and give examples proving that the converse is not true. We characterize when the 2-homogeneous, diagonal polynomials on p(1 < p ) are r-dominated. We prove that, unlike the linear case, there are nuclear polynomials which are not 1-dominated.Received: 6 June 2004; revised: 28 September 2004 相似文献
73.
Christophe Vande Velde Evi Bultinck Karla Tersago Christian Van Alsenoy Frank Blockhuys 《International journal of quantum chemistry》2007,107(3):670-679
Unhindered ortho‐dimethoxy‐substituted phenyl rings often display a coplanar conformation. A theoretical study of a series of methoxybenzenes consisting of methoxybenzene (anisole), the three dimethoxybenzenes, and 1,2,4,5‐tetramethoxybenzene, at the DFT/B3LYP/6‐311++G** level of theory, allows us to identify the factors influencing the conformational preference and attribute the coplanarity of such methoxy groups to mesomeric effects. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
74.
Ramirez E Cabeza M Heuze I Gutiérrez E Bratoeff E Membrillo M Lira A 《Chemical & pharmaceutical bulletin》2002,50(1):15-20
The pharmacological activity of several new pregnane derivatives 15-19 were determined on gonadectomized male hamster flank organs, seminal vesicles and in vitro conversion of testosterone (T) to dihydrotestosterone (DHT) as 5alpha-reductase inhibitors. Steroids 15-19 decreased the diameter of the pigmented spot in the flank organs as compared to the T treated animals; in this model, steroids 16 and 19 showed a higher activity than the commercially available finasteride 3. Injection of T increased the weight of the seminal vesicles. Compounds 15-19 when injected together with T decreased the weight of the seminal vesicles thus showing an antiandrogenic effect. The trienone 19 exhibited a considerably higher activity than finasteride. Steroids 15-19 inhibited the in vitro metabolism of [3H]T to [3H]DHT in seminal vesicles homogenates of gonadectomized male hamsters. Compounds 18 and 19 showed a much higher antiandrogenic effect than finasteride. This enhancement of the biological activity could probably be attributed to the coplanarity of the steroidal skeleton as previously observed by our group. The high antiandrogenic activity of the epoxy compound 16 is probably the result of the ring opening of the oxiran ring with the nucleophilic part of the enzyme 5alpha-reductase thus leading to a stable adduct with concomitant deactivation of this enzyme. 相似文献
75.
Maddox AF Erickson KA Tanski JM Waterman R 《Chemical communications (Cambridge, England)》2011,47(42):11769-11771
Reaction of (N(3)N)ZrX complexes (X = amido, Cl(-), CH(3)(-)) with carbodiimide substrates results in insertion into an Zr-N bond of the triamidoamine ligand rather than the Zr-X bond as has been observed for related (N(3)N)ZrX complexes (X = PR(2)(-), AsR(2)(-)). 相似文献
76.
Willem Jespers Dr. Grégory Verdon Dr. Jhonny Azuaje Dr. Maria Majellaro Dr. Henrik Keränen Prof. Xerardo García-Mera Dr. Miles Congreve Dr. Francesca Deflorian Dr. Chris de Graaf Dr. Andrei Zhukov Dr. Andrew S. Doré Dr. Jonathan S. Mason Prof. Johan Åqvist Dr. Robert M. Cooke Prof. Eddy Sotelo Dr. Hugo Gutiérrez-de-Terán 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16679-16686
We present a robust protocol based on iterations of free energy perturbation (FEP) calculations, chemical synthesis, biophysical mapping and X-ray crystallography to reveal the binding mode of an antagonist series to the A2A adenosine receptor (AR). Eight A2AAR binding site mutations from biophysical mapping experiments were initially analyzed with sidechain FEP simulations, performed on alternate binding modes. The results distinctively supported one binding mode, which was subsequently used to design new chromone derivatives. Their affinities for the A2AAR were experimentally determined and investigated through a cycle of ligand-FEP calculations, validating the binding orientation of the different chemical substituents proposed. Subsequent X-ray crystallography of the A2AAR with a low and a high affinity chromone derivative confirmed the predicted binding orientation. The new molecules and structures here reported were driven by free energy calculations, and provide new insights on antagonist binding to the A2AAR, an emerging target in immuno-oncology. 相似文献
77.
D. Blanco Gomis A M Picinelli Lobo M. D. Gutiérrez Alvarez J. J. Mangas Alonso 《Chromatographia》1990,29(3-4):155-160
Summary A rapid and sensitive method for the simultaneous determination of primary amino acids in apple is described. After sample preparation, amino acids were derivatized with o-phthaldialdehyde/2-mercaptoethanol and separated on a reversed phase column with a gradient of phosphate buffer-tetrahydrofuran-methanol as the mobile phase. Detection was carried out with a fluorescence detector at excitation and emission wavelengths of 340 nm and 425 nm respectively. Recovery studies showed good results for all substances (91–109%) (with coefficients of variation ranging, from 0.1 to 9.0%). This method was applied to the monitoring of amino acids during the ripening of apples. 相似文献
78.
Chinchilla D Zavaleta J Martinez K Gomez FA 《Analytical and bioanalytical chemistry》2005,383(4):625-631
Multiple-injection affinity capillary electrophoresis (MIACE) is used to determine binding constants (K
b) between receptors and ligands using as model systems vancomycin and teicoplanin from Streptomyces orientalis and Actinoplanes teichomyceticus, respectively, and their binding to D-Ala-D-Ala peptides and carbonic anhydrase B (CAB. EC 4.2.1.1) and the binding of the latter to arylsulfonamides. A sample plug
containing a non-interacting standard is first injected followed by multiple plugs of sample containing the receptor and then
a final injection of sample containing a second standard. Between each injection of sample, a small plug of buffer is injected
which contains an increasing concentration of ligand to effect separation between the multiple injections of sample. Electrophoresis
is then carried out in an increasing concentration of ligand in the running buffer. Continued electrophoresis results in a
shift in the migration time of the receptor in the sample plugs upon binding to their respective ligand. Analysis of the change
in the relative migration time ratio (RMTR) or electrophoretic mobility (μ) of the resultant receptor–ligand complex relative to the non-interacting standards, as a function of the concentration of
ligand yields a value for K
b. The MIACE technique is a modification in the ACE method that allows for the estimation of binding affinities between biological
interactions on a timescale faster than that found for standard ACE. In addition sample volume requirements for the technique
are reduced compared to traditional ACE assays. These findings demonstrate the advantage of using MIACE to estimate binding
parameters between receptors and ligands. 相似文献
79.
Jose Zavaleta Alejandra Ramirez Karla Martinez John E. Ladbury Frank A. Gomez 《Talanta》2007,71(1):192-201
Partial filling multiple injection affinity capillary electrophoresis (PFMIACE) is used to determine binding constants between vancomycin (Van) from Streptomyces orientalis, teicoplanin (Teic) from Actinoplanes teicomyceticus and ristocetin (Rist) from Nocardia lurida to d-Ala-d-Ala terminus peptides and carbonic anhydrase B (CAB, E.C.4.2.1.1) to arylsulfonamides. Two variations of PFMIACE are described herein. In the first technique, the capillary is partially filled with ligand at increasing concentrations, a non-interacting standard, three or four separate plugs of receptor each separated by small plugs of buffer, a plug containing a second non-interacting standard, and then electrophoresed in buffer. Upon continued electrophoresis, equilibrium is established between the ligand and receptors causing a shift in the migration time of the receptors with respect to the non-interacting standards. This change in migration time is utilized for estimating multiple binding constants (Kb) for the same interaction. In the second technique, separate plugs of sample containing non-interacting standards, peptide one, buffer, and peptide two, were injected into the capillary column. The capillary is partially filled with a series of buffers containing an antibiotic at increasing concentrations and electrophoresed. Peptides migrate through the column at similar electrophoretic mobilities since their charge-to-mass ratios are approximately the same but remain as distinct zones due to the buffer plug between peptides. Upon electrophoresis, the plug of antibiotic flows into the peptide plugs affecting a shift in the migration time of the peptides with respect to the non-interacting standards occurs due to formation of the of the antibiotic-peptide complex. The shift in the migration time of the peptides upon binding to the antibiotic is used for the Scatchard analysis and measurement of a Kb. The PFMIACE technique expands the functionality and potential of ACE as an analytical tool to examine receptor-ligand interactions. In PFMIACE, a smaller amount of sample is required in the assay compared to both conventional ACE and MIACE. Furthermore, a wide array of data is obtained from a single experiment, thus, expediting the assay of biological species. 相似文献
80.
Mehrdad Pourayoubi Atekeh Tarahhomi Fatemeh Karimi Ahmadabad Karla Fejfarová Arie van der Lee Michal Dušek 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(4):o164-o169
In N,N′‐di‐tert‐butyl‐N′′,N′′‐dimethylphosphoric triamide, C10H26N3OP, (I), and N,N′,N′′,N′′′‐tetra‐tert‐butoxybis(phosphonic diamide), C16H40N4O3P2, (II), the extended structures are mediated by P(O)...(H—N)2 interactions. The asymmetric unit of (I) consists of six independent molecules which aggregate through P(O)...(H—N)2 hydrogen bonds, giving R21(6) loops and forming two independent chains parallel to the a axis. Of the 12 independent tert‐butyl groups, five are disordered over two different positions with occupancies ranging from to . In the structure of (II), the asymmetric unit contains one molecule. P(O)...(H—N)2 hydrogen bonds give S(6) and R22(8) rings, and the molecules form extended chains parallel to the c axis. The structures of (I) and (II), along with similar structures having (N)P(O)(NH)2 and (NH)2P(O)(O)P(O)(NH)2 skeletons extracted from the Cambridge Structural Database, are used to compare hydrogen‐bond patterns in these families of phosphoramidates. The strengths of P(O)[...H—N]x (x = 1, 2 or 3) hydrogen bonds are also analysed, using these compounds and previously reported structures with (N)2P(O)(NH) and P(O)(NH)3 fragments. 相似文献