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51.
Kazi A. Azam Mohitosh Bhowmick Golam Mohammad Golzar Hossain Shariff E. Kabir Kalipada Kundu Khalifa Mohammad Abdul Malik Salina Perven 《Journal of chemical crystallography》2001,31(1):63-68
Treatment of [Ru3(CO)10(-dppm)] (1) with the ditelluride Te2(C6H4OEt-4)2 in refluxing toluene afforded the new aryltellurol bridged complex [Ru2(CO)4(-TeC6H4OEt-4)2 (-dppm)] (2) together with three known complexes [Ru4(CO)8(-CO)(4-Te)2(-dppm)] (3), [Ru2(CO)6{-CH2PPh(C6H4)PPh}] (4), and [Ru2(CO)6{-C6H4PPh(CH2)PPh}] (5). All the four complexes were characterized by spectroscopic methods, including an X-ray structure determination for 5. Complex 5 crystallizes in the monoclinic space group P21/c with a = 13.650(2), b = 9.995(2), c = 18.929(3) Å, = 97.49(2)°, V = 2560.4(8) Å3, and Z = 4. In this complex the two ruthenium atoms are bridged by the phosphino-phosphide ligand C6H4PPh(CH2)PPh which is attached to one Ru by the C6H4 group and a P atom while to the other Ru by both the two P atoms. Both the ruthenium atoms show distorted octahedral geometry. The Ru—Ru bond length is 2.8719(7) Å. 相似文献
52.
The strengthening of the hydrogen bonding (H-bond) network as well as transition from the tetrahedral-like water network to
the zigzag chain structure of alcohol upon increasing the alcohol concentration in ethanol-water and tertiary butanol (TBA)
— water mixtures have been studied by using both steady state and time resolved spectroscopy. Absorption and emission characteristics
of coumarin 153 (C153), a widely used non-reactive solvation probe, have been monitored to investigate the structural transition
in these binary mixtures. The effects of the hydrogen bond (H-bond) network with alcohol concentration are revealed by a minimum
in the peak frequency of the absorption spectrum of C153 which occur at alcohol mole fraction ∼0·10 for water-ethanol and
at ∼0·04 for water-TBA mixtures. These are the mole fractions around which several thermodynamic properties of these mixtures
show anomalous change due to the enhancement of H-bonding network. While the strengthening of H-bond network is revealed by
the absorption spectra, the emission characteristics show the typical non-ideal alcohol mole fraction dependence at all concentrations.
The time resolved anisotropy decay of C153 has been found to be bi-exponential at all alcohol mole fractions. The sharp change
in slopes of average rotational correlation time with alcohol mole fraction indicates the structural transition in the environment
around the rotating solute. The changes in slopes occur at mole fraction ∼0·10 for TBA-water and at ∼0·2 for ethanol-water
mixtures, which are believed to reflect alcohol mole fraction induced structural changes in these alcohol-water binary mixtures. 相似文献
53.
Pyramidal indentations and focused-ion-beam machining have been used to study the damage during contact loading of textured columnar titanium nitride hard coatings on three steels and aluminium. The influence of the substrate hardness and coating thickness on the type and extent of fracture have been examined. In particular, the primary mechanism of deformation is shown to undergo a change from inter-columnar shear to other forms of subsurface damage. A physical model is proposed to explain this transition in the fracture mode. The implications of such behaviour for coating design are discussed. 相似文献
54.
Tuhin Patra Peter Bellotti Felix Strieth‐Kalthoff Frank Glorius 《Angewandte Chemie (International ed. in English)》2020,59(8):3172-3177
An intermolecular, two‐component vicinal carboimination of alkenes has been accomplished by energy transfer catalysis. Oxime esters of alkyl carboxylic acids were used as bifunctional reagents to generate both alkyl and iminyl radicals. Subsequently, addition of the alkyl radical to an alkene generates a transient radical for selective radical–radical cross‐coupling with the persistent iminyl radical. Furthermore, this process provides direct access to aliphatic primary amines and α‐amino acids by simple hydrolysis. 相似文献
55.
Huaqing Chen Biswajit Bhowmick Yu Tang Jesus Lozano-Fernandez Qian Han 《Molecules (Basel, Switzerland)》2022,27(15)
A specific mosquito enzyme, 3-hydroxykynurenine transaminase (HKT), is involved in the processing of toxic metabolic intermediates of the tryptophan metabolic pathway. The HKT enzymatic product, xanthurenic acid, is required for Plasmodium spp. development in the mosquito vectors. Therefore, an inhibitor of HKT may not only be a mosquitocide but also a malaria-transmission blocker. In this work, we present a study investigating the evolution of HKT, which is a lineage-specific duplication of an alanine glyoxylate aminotransferases (AGT) in mosquitoes. Synteny analyses, together with the phylogenetic history of the AGT family, suggests that HKT and the mosquito AGTs are paralogous that were formed via a duplication event in their common ancestor. Furthermore, 41 amino acid sites with significant evidence of positive selection were identified, which could be responsible for biochemical and functional evolution and the stability of conformational stabilization. To get a deeper understanding of the evolution of ligands’ capacity and the ligand-binding mechanism of HKT, the sequence and the 3D homology model of the common ancestor of HKT and AGT in mosquitoes, ancestral mosquito AGT (AncMosqAGT), were inferred and built. The homology model along with 3-hydroxykynurenine, kynurenine, and alanine were used in docking experiments to predict the binding capacity and ligand-binding mode of the new substrates related to toxic metabolites detoxification. Our study provides evidence for the dramatic biochemical evolution of the key detoxifying enzyme and provides potential sites that could hinder the detoxification function, which may be used in mosquito larvicide and design. 相似文献
56.
Jesse Murillo Rina Bhowmick Katie L. M. Harriman Alejandra Gomez-Torres Joshua Wright Robert W. Meulenberg Pere Mir Alejandro Metta-Magaa Muralee Murugesu Bess Vlaisavljevich Skye Fortier 《Chemical science》2021,12(40):13360
Addition of [UI2(THF)3(μ-OMe)]2·THF (2·THF) to THF solutions containing 6 equiv. of K[C14H10] generates the heteroleptic dimeric complexes [K(18-crown-6)(THF)2]2[U(η6-C14H10)(η4-C14H10)(μ-OMe)]2·4THF (118C6·4THF) and {[K(THF)3][U(η6-C14H10)(η4-C14H10)(μ-OMe)]}2 (1THF) upon crystallization of the products in THF in the presence or absence of 18-crown-6, respectively. Both 118C6·4THF and 1THF are thermally stable in the solid-state at room temperature; however, after crystallization, they become insoluble in THF or DME solutions and instead gradually decompose upon standing. X-ray diffraction analysis reveals 118C6·4THF and 1THF to be structurally similar, possessing uranium centres sandwiched between bent anthracenide ligands of mixed tetrahapto and hexahapto ligation modes. Yet, the two complexes are distinguished by the close contact potassium-arenide ion pairing that is seen in 1THF but absent in 118C6·4THF, which is observed to have a significant effect on the electronic characteristics of the two complexes. Structural analysis, SQUID magnetometry data, XANES spectral characterization, and computational analyses are generally consistent with U(iv) formal assignments for the metal centres in both 118C6·4THF and 1THF, though noticeable differences are detected between the two species. For instance, the effective magnetic moment of 1THF (3.74 μB) is significantly lower than that of 118C6·4THF (4.40 μB) at 300 K. Furthermore, the XANES data shows the U LIII-edge absorption energy for 1THF to be 0.9 eV higher than that of 118C6·4THF, suggestive of more oxidized metal centres in the former. Of note, CASSCF calculations on the model complex {[U(η6-C14H10)(η4-C14H10)(μ-OMe)]2}2− (1*) shows highly polarized uranium–arenide interactions defined by π-type bonds where the metal contributions are primarily comprised by the 6d-orbitals (7.3 ± 0.6%) with minor participation from the 5f-orbitals (1.5 ± 0.5%). These unique complexes provide new insights into actinide–arenide bonding interactions and show the sensitivity of the electronic structures of the uranium atoms to coordination sphere effects.Use of Chatt metal-arene protocols with uranium leads to the synthesis of the first well-characterized, unsupported actinide–arenide sandwich complexes. The electronic structures of the actinide centres show a key sensitivity to ion pairing effects. 相似文献
57.
A steady state thermoelastic mixed boundary value problem for an isotropic thick plate is considered in this paper. The faces
of an external circular crack situated in the mid-plane of the plate are opened up by the application of temperature while
the bounding surface of the plate are maintained at a constant zero temperature. Solution valid for large values of the ratio
of the plate thickness to the diameter of the crack has been obtained. Expressions for various quantities of physical interest
are derived by finding iterative solutions of the equations and the results are shown graphically. 相似文献
58.
An axisymmetric steady-state thermoelastic problem of an infinite isotropic medium containing an annular crack is considered.
The faces of the crack are exposed to prescribed temperature distribution. The normal components of stress and displacement
on the crack plane and the stress-intensity factors at the boundaries of the crack are expressed in power series in terms
of the ratio between the radii of the inner and outer boundaries. These are illustrated graphically. 相似文献
59.
Gayathri Kolliyedath Tuhin Sahana Silpa Mary Johnson Dr. Subrata Kundu 《Angewandte Chemie (International ed. in English)》2023,62(50):e202313187
(Per)thionitrite (SNO−/SSNO−) intermediates play vital roles in modulating nitric oxide (NO) and hydrogen sulfide (H2S) dependent bio-signalling processes. Whilst the previous preparations of such intermediates involved reactive H2S/HS− or sulfane sulfur (S0) species, the present report reveals that relatively stable thiocarbonyl compounds (such as carbon disulfide (CS2), thiocarbamate, thioacetic acid, and thioacetate) react with nitrite anion to yield SNO−/SSNO−. For instance, the reaction of CS2 and nitrite anion (NO2−) under ambient condition affords CO2 and SNO−/SSNO−. A detailed investigation involving UV/Vis, FTIR, HRMS, and multinuclear NMR studies confirm the formation of SNO−/SSNO−, which are proposed to form through an initial nucleophilic attack by nitrite anion followed by a transnitrosation step. Notably, reactions of CS2 and nitrite in the presence of thiol RSH show the formation of organic polysulfides R-Sn-R, thereby illustrating that the thiocarbonyls are capable of influencing the pool of bioavailable sulfane sulfurs. Furthermore, the availability of both NO2− and thiocarbonyl motifs in the biological context hints at their synergistic metal-free activations leading to the generation of NO gas and various reactive sulfur species via SNO−/SSNO−. 相似文献
60.
Metal-based netropsin mimics showing AT-selective DNA binding and DNA cleavage activity at red light
Copper(II) bis-arginate [Cu(l-arg)2](NO3)2 (1) and [Cu(l-arg)(phen)Cl]Cl (2) as mimics of the minor-groove-binding natural antibiotic netropsin show preferential binding to the AT-rich region of double-stranded DNA. The complexes with a d-d band near 600 nm display oxidative DNA cleavage activity on photoirradiation at UV-A light of 365 nm and at red light of 647.1 nm (Ar-Kr laser) in a metal-assisted photoexcitation process forming singlet oxygen (1O2) species in a type-2 pathway. 相似文献