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71.
Tobias Baumann Matthias Hauf Fabian Schildhauer Katharina B. Eberl Patrick M. Durkin Erhan Deniz Jan G. Lffler Carlos G. Acevedo‐Rocha Jelena Jaric Berta M. Martins Holger Dobbek Jens Bredenbeck Nediljko Budisa 《Angewandte Chemie (International ed. in English)》2019,58(9):2899-2903
Allosteric information transfer in proteins has been linked to distinct vibrational energy transfer (VET) pathways in a number of theoretical studies. Experimental evidence for such pathways, however, is sparse because site‐selective injection of vibrational energy into a protein, that is, localized heating, is required for their investigation. Here, we solved this problem by the site‐specific incorporation of the non‐canonical amino acid β‐(1‐azulenyl)‐l ‐alanine (AzAla) through genetic code expansion. As an exception to Kasha's rule, AzAla undergoes ultrafast internal conversion and heating after S1 excitation while upon S2 excitation, it serves as a fluorescent label. We equipped PDZ3, a protein interaction domain of postsynaptic density protein 95, with this ultrafast heater at two distinct positions. We indeed observed VET from the incorporation sites in the protein to a bound peptide ligand on the picosecond timescale by ultrafast IR spectroscopy. This approach based on genetically encoded AzAla paves the way for detailed studies of VET and its role in a wide range of proteins. 相似文献
72.
Vladimir Iashin Dénes Berta Konstantin Chernichenko Martin Nieger Karina Moslova Imre Pápai Timo Repo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(61):13873-13879
Organoboron compounds are essential reagents in modern C−C coupling reactions. Their synthesis via catalytic C−H borylation by main group elements is emerging as a powerful tool alternative to transition metal based catalysis. Herein, a straightforward metal-free synthesis of aryldifluoroboranes from BF3 and heteroarenes is reported. The reaction is assisted by sterically hindered amines and catalytic amounts of thioureas. According to computational studies the reaction proceeds via frustrated Lewis pair (FLP) mechanism. The obtained aryldifluoroboranes are further stabilized against destructive protodeborylation by converting them to the corresponding air stable tetramethylammonium organotrifluoroborates. 相似文献
73.
Rare earth arenedisulfonate metal-organic frameworks: an approach toward polyhedral diversity and variety of functional compounds 总被引:1,自引:0,他引:1
Gándara F García-Cortés A Cascales C Gómez-Lor B Gutiérrez-Puebla E Iglesias M Monge A Snejko N 《Inorganic chemistry》2007,46(9):3475-3484
Eight 2D and 3D metal-organic framework (MOF) rare earth naphthalenedisulfonates have been obtained. The different geometry of the naphthalenedisulfonic acids used as connectors [(1,5-NDS) and (2,6-NDS)] gives rise to the three new structure types. In Ln(OH)(1,5-NDS)H2O, LnPF-1 (lanthanide polymeric framework; Ln=La, Nd, Pr, Sm and Eu), the lanthanide ion is octacoordinated. Its 3D structure is formed by (Ln2O14)-S-(Ln2O14) infinite chains, connected through complete NDS connectors. LnPF-2 (Ln=Nd), with the same empirical formula as the former, and the lanthanide in octa- and nonacoordination, owns an arrangement of sulfonate bridges and neodymium polyhedra that gives rise to a 2D structure. [Ln5(2,6-NDS)3(OH)9(H2O)4](H2O)2, LnPF-3 (Ln=Nd, Eu), demonstrates that it is possible to obtain a 3D structure with (2,6-NDS), when a greater Ln/connector ratio is employed. It is worth pointing out the existence, in this latter family of compounds, of a mu5-OH group, whose hydrogen atom is very close to one-sixth Ln atom (distance Ln...H=2.09 A). The materials, with high thermal stability, act as active and selective bifunctional heterogeneous catalysts in oxidation of linalool yielding cyclic hydroxy ethers. The absence of any 3D Nd-Nd magnetic interaction is explained due to the inner nature of 4f orbitals of Nd3+, which do not favor the magnetic exchange. The influence of the polymeric frame matrix results in a better photoluminescence efficiency for NdPF-1. 相似文献
74.
A general method for polymer-assisted solution-phase (PASP) Suzuki reactions employing a combination of anthracene-tagged palladium catalyst and anthracene-tagged boronic acid with a polymer-supported carbonate base is reported. The anthracene-tagged catalyst allows for the easy removal of the Pd catalyst along with the dissociated phosphine ligand and phosphine oxide byproducts by sequestration through a chemoselective Diels-Alder reaction with a maleimide resin. The polymer-supported carbonate base facilitates the removal of excess boronic acid and the borane-containing byproducts present at the end of the coupling reaction. The Suzuki coupling reaction can be efficiently conducted by using combinations of the anthracene-tagged Pd catalyst, polymer-supported carbonate base, and anthracene-tagged boronic acid to yield the desired product in high purity and yield without the use of chromatography. 相似文献
75.
Berta Barta Holló Katalin Mészáros Szécsényi Mária Deli Lóránd Kiss Alfréd Kállay-Menyhárd Vukosava Živković-Radovanović Zoran D. Tomić 《Structural chemistry》2016,27(4):1121-1133
Synthetic paths toward the two polymorphs of a monohydrate, one anhydrous polymorph of 1-carboxamidino-5-hydroxy-3-methylpyrazole (hcmp) and two polymorphs of zinc complexes containing hcmp ligand are presented. By choosing ions which are not part of the final product, it is possible to direct the synthesis toward the particular polymorph. In all three modifications of hcmp, the same hydrogen bonding motif appears, leading to formation of similar molecular chains. Differences arise due to different modes of chain aggregation and the presence of solvent water. Analysis of the crystal packing and the energetic features of hcmp polymorphs is made using the PIXEL model. The thermal decomposition processes are examined using differential scanning calorimetry and thermogravimetry. Analysis of crystal packing in the two polymorphs of zinc complex suggests the key role of the hydrogen bonding capacity of the aqua ligand for the appearance of the two polymorphic forms. In both polymorphs of zinc complex, stacking interactions have an important role. However, the enhanced hydrogen bonding capacity of the aqua ligand influences the formation of multistacking arrangement. 相似文献
76.
A new rigid bidentate ligand, bis(1-naphthylimino)acenaphthene, L1, and its Zn(II) and Pd(II) complexes [ZnCl 2( L1)], 1, and [PdCl 2( L1)], 2, were synthesized. L1 was prepared by the "template method", reacting 1-naphthyl amine and acenaphthenequinone in the presence of ZnCl 2, giving 1, which was further demetallated. Reaction of 1-naphthyl amine with acenaphthenequinone and PdCl 2 afforded dichloride bis(1-naphthyl)acenaphthenequinonediimine palladium, 2. L1, 1, and 2 were obtained as a mixture of syn and anti isomers. Compound 2 was also obtained by the reaction of PdCl 2 activated by refluxing it in acetonitrile followed by the addition of L1; by this route also a mixture of syn and anti isomers was obtained, but at a different rate. The solid-state structures of L1 and the anti isomer of compound 2 have been determined by single-crystal X-ray diffraction. All compounds have been characterized by elemental analyses; matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry; IR; UV-vis; (1)H, (13)C, and (1)H- (1)H correlation spectroscopy; (1)H- (13)C heteronuclear single quantum coherence; (1)H- (13)C heteronuclear single quantum coherence-total correlation spectroscopy; and (1)H- (1)H nuclear Overhauser effect spectrometry NMR spectroscopies when applied. Density functional theory studies showed that both conformers for [PdCl 2(BIAN)] are isoenergetic, and they can both be obtained experimentally. However, we can predict that the isomerization process is not available in a square-planar complex, but it is possible for the free ligand. The molecular geometry is very similar in both isomers, and only different orientations for naphthyl groups can be expected. 相似文献
77.
Dr. Jose R. Magana Dr. Berta Gumí-Audenis Dr. Roderick P. Tas Levena Gascoigne Dr. Dylan L. Atkins Prof. Ilja K. Voets 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(66):15330-15336
Silica materials attract an increasing amount of interest in (fundamental) research, and find applications in, for example, sensing, catalysis, and drug delivery. As the properties of these (nano)materials not only depend on their chemistry but also their size, shape, and surface area, the controllable synthesis of silica is essential for tailoring the materials to specific applications. Advantageously, bioinspired routes for silica production are environmentally friendly and straightforward since the formation process is spontaneous and proceeds under mild conditions. These strategies mostly employ amine-bearing phosphorylated (bio)polymers. In this work, we expand this principle to supramolecular polymers based on the water-soluble cationic cyanine dye Pinacyanol acetate. Upon assembly in water, these dye molecules form large, polyaminated, supramolecular fibers. The surfaces of these fibers can be used as a scaffold for the condensation of silicic acid. Control over the ionic strength, dye concentration, and silicic acid saturation yielded silica fibers with a diameter of 25 nm and a single, 4 nm pore. Unexpectedly, other unusual superstructures, namely, nummulites and spherulites, are also observed depending on the ionic strength and dye concentration. Transmission and scanning electron microscopy (TEM and SEM) showed that these superstructures are formed by aligned silica fibers. Close examination of the dye scaffold prior silicification using small-angle X-ray scattering (SAXS), and UV/Vis spectroscopy revealed minor influence of the ionic strength and dye concentration on the morphology of the supramolecular scaffold. Total internal reflection fluorescence (TIRF) during silicification unraveled that if the reaction is kept under static conditions, only silica fibers are obtained. Experiments performed on the dye scaffold and silica superstructures evidenced that the marked structural diversity originates from the arrangement of silica/dye fibers. Under these mild conditions, external force fields can profoundly influence the morphology of the produced silica. 相似文献
78.
79.
Conformational analysis of 1-amino-3-butene and 3-butene-1-thiol was carried out using the 4-21G basis set. The conformers obtained were subjected to 6-31G* single-point analysis for the calculation of energies, charge distributions, and dipole moments. The geometries and stabilities obtained are in good agreement with available experimental data. The results are interpreted in terms of intramolecular hydrogen bonding and anomeric interactions: Some of the most stable conformers of both molecules have intramolecular hydrogen bonds between the hydrogens of the amino or thiol groups and the electrons of the double bond. The 4-21G geometries were refined to obtain rotational constants closer to the experimental values. 相似文献
80.
Metallation of thiols RFC2H4SH followed by alkylation with iodides R′FC2H4I leads either to symmetrical or to unsymmetrical sulphides RFC2H4SC2H4R′F (with RF=R′F or RF ≠ R′F). All compounds obtained are good solvents of gases (particularly O2, CO, CO2, N2).This property allows their application as biological carriers of dissolved gases. 相似文献