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Van der waal

Fatemeh Khosravi, Hassan Mansouri-Torshizi
Four Co(III)-, Cu(II)-, Zn(II)- and Pd(II)- based potent antibacterial complexes of formula K3[Co(ox)3].3H2O (I), [Cu(bpy)2Cl]Cl.5H2O (II), [Zn(bpy)3]Cl2 (III) and [Pd(bpy)2](NO3)2 (IV) (where ox is oxalate and bpy is 2,2'-bipyridine) were synthesized. They were characterized by elemental analyses, molar conductance measurements, UV-Vis, FT-IR, (1)H NMR and (13)C NMR spectra. These metal complexes were ordered in three combination series of I+II, I+II+III and I+II+III+IV. Antibacterial activity was tested for each of these four metal complexes and their combinations against gram positive and gram negative bacteria...
January 16, 2017: Journal of Biomolecular Structure & Dynamics
Svetlana A Malinovskaya
Quantum control methodology is presented to design many-body spin states in a spin chain of Rydberg atoms using laser pulses and a magnetic field. A two-photon ladder-type configuration is implemented, which is advantageous due to the combined action of the one-photon and two-photon detunings as control parameters. Many-body spin states are designed consisting of an ensemble of spins encoded in sublevels of Rydberg states and coupled via the van der Waals interactions.
January 15, 2017: Optics Letters
Huan He, Juan Xu, Dan-Yang Cheng, Li Fu, Yu-Shu Ge, Feng-Lei Jiang, Yi Liu
Amino naphthalene 2-Cyanoacrylate (ANCA) probe is a kind of fluorescent amyloid binding probe that can report a different fluorescence emission when bound to different types of amyloid deposits in tissue, while their interactions with amyloid fibrils remain unclear due to the insoluble nature of amyloid fibrils. Here, all atom molecular dynamics simulations were used to investigate the interaction between ANCA probes with three different amyloid fibrils. Two common binding modes of ANCA probes on Aβ40 amyloid fibrils were identified by cluster analysis of multiple simulations...
January 12, 2017: Journal of Physical Chemistry. B
Christina R Forbes, Sudipta Kumar Sinha, Himal Kanti Ganguly, Shi Bai, Glenn P A Yap, Sandeep Patel, Neal J Zondlo
Thiols can engage favorably with aromatic rings in S-H/π interactions, within abiological systems and within proteins. However, the underlying bases for S-H/π interactions are not well understood. The crystal structure of Boc-L-4-thiolphenylalanine tert-butyl ester revealed crystal organization centered on the interaction of the thiol S-H with the aromatic ring of an adjacent molecule, with a through-space Hthiol...Caromatic distance of 2.71 Å, below the 2.90 Å sum of the van der Waals radii of H and C...
January 12, 2017: Journal of the American Chemical Society
Zonglin Gu, Phil De Luna, Zaixing Yang, Ruhong Zhou
Molybdenum disulfide (MoS2) has recently emerged as a promising nanomaterial in a wide range of applications due to its unique and impressive properties. For example, MoS2 has gained attention in the biomedical field because of its ability to act as an antibacterial and anticancer agent. However, the potential influence of this exciting nanomaterial on biomolecules is yet to be extensively studied. Molecular dynamics (MD) simulations are invaluable tools in the examination of protein interactions with nanomaterials such as MoS2...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
Marko Pavlovic, Paul Rouster, Elodie Bourgeat-Lami, Vanessa Prevot, Istvan Szilagyi
Colloidal stability of polymeric latex particles was studied in the presence of oppositely charged layered double hydroxide (LDH) platelets of different interlayer anions. Adsorption of the LDH particles led to charge neutralization and to overcharging of the latex at appropriate concentrations. Mixing stable colloidal suspensions of individual particles results in rapid aggregation once the LDH adsorption neutralizes the negative charges of the polymer spheres, while stable suspensions were observed at high and low LDH doses...
January 12, 2017: Soft Matter
Takuya Iwasaki, Manoharan Muruganathan, Marek E Schmidt, Hiroshi Mizuta
The transformation of systematic vacuum and hydrogen annealing effects in graphene devices on the SiO2 surface is reported based on experimental and van der Waals interaction corrected density functional theory (DFT) simulation results. Vacuum annealing removes p-type dopants and reduces charged impurity scattering in graphene. Moreover, it induces n-type doping into graphene, leading to the improvement of the electron mobility and conductivity in the electron transport regime, which are reversed by exposing to atmospheric environment...
January 11, 2017: Nanoscale
Stephanie Bettis Homan, Vinod K Sangwan, Itamar Balla, Hadallia Bergeron, Emily A Weiss, Mark C Hersam
van der Waals heterojunctions between two-dimensional (2D) layered materials and nanomaterials of different dimensions present unique opportunities for gate-tunable optoelectronic devices. Mixed-dimensional p-n heterojunction diodes, such as p-type pentacene (0D) and n-type monolayer MoS2 (2D), are especially interesting for photovoltaic applications where the absorption cross-section and charge transfer processes can be tailored by rational selection from the vast library of organic molecules and 2D materials...
January 11, 2017: Nano Letters
Shubhaditya Majumdar, Jonathan A Malen, Alan J H McGaughey
The effect of the local molecular environment on thermal transport through organic-inorganic heterojunctions is investigated using binary self-assembled monolayer (SAM) junctions built from a mixture of alkanethiol and alkanedithiol species sandwiched between gold leads. Thermoreflectance measurements and molecular dynamics simulations demonstrate that the thermal conductances of the binary SAM junctions vary with molecular composition and are greater than predictions of a parallel resistance model. The enhancement results from increased thermal transport through the alkanethiols, whose terminal methyl groups are confined by the anchored alkanedithiols...
January 11, 2017: Nano Letters
Guanxiong Liu, Sergey Rumyantsev, Matthew A Bloodgood, Tina T Salguero, Michael Shur, Alexander A Balandin
We report results of investigation of the low-frequency electronic excess noise in quasi-1D nanowires of TaSe3 capped with quasi-2D h-BN layers. Semimetallic TaSe3 is a quasi-1D van der Waals material with exceptionally high breakdown current density. It was found that TaSe3 nanowires have lower levels of the normalized noise spectral density, SI/I(2), compared to carbon nanotubes and graphene (I is the current). The temperature-dependent measurements revealed that the low-frequency electronic 1/f noise becomes the 1/f(2) type as temperature increases to ∼400 K, suggesting the onset of electromigration (f is the frequency)...
January 11, 2017: Nano Letters
Li-Yang Cheng, Min Fang, Ai-Min Bai, Yu Ouyang, Yan-Jun Hu
In this study, fluorescence spectroscopy and molecular modeling approaches were employed to investigate the binding of methotrexate to human serum albumin (HSA) under physiological conditions. From the mechanism, it was demonstrated that fluorescence quenching of HSA by methotrexate results from the formation of a methotrexate/HSA complex. Binding parameters calculated using the Stern-Volmer method and the Scatchard method showed that methotrexate binds to HSA with binding affinities in the order 10(4)  L·mol(-1) ...
January 10, 2017: Luminescence: the Journal of Biological and Chemical Luminescence
Zhongkai Zhou, Jingjing Xu, Yuqian Liu, Demei Meng, Xiaoli Sun, Hong Yi, Yunjing Gao, Guoyu Sun, Padraig Strappe, Chris Blanchard, Rui Yang
Rice bran albumin protein (RAP) is sensitive to thermal changes and tends to degrade when exposed to high-temperature processing. In this work, RAP-epigallocatechin-3-gallate (EGCG) complex (RAPE) was prepared and the thermal stability was evaluated. Fluorescence results showed that EGCG could interact with RAP with a binding number n of 0.0885:1 (EGCG:RAP, w/w) and a binding constant K of 1.02 (± 0.002) ×10(4) /M, suggesting both hydrogen bonding and van der Waals forces played an important role. FTIR analysis demonstrated that EGCG could induce secondary structural changes in RAP above a ratio of 1...
January 10, 2017: Journal of Food Science
Chendong Zhang, Chih-Piao Chuu, Xibiao Ren, Ming-Yang Li, Lain-Jong Li, Chuanhong Jin, Mei-Yin Chou, Chih-Kang Shih
By using direct growth, we create a rotationally aligned MoS2/WSe2 hetero-bilayer as a designer van der Waals heterostructure. With rotational alignment, the lattice mismatch leads to a periodic variation of atomic registry between individual van der Waals layers, exhibiting a Moiré pattern with a well-defined periodicity. By combining scanning tunneling microscopy/spectroscopy, transmission electron microscopy, and first-principles calculations, we investigate interlayer coupling as a function of atomic registry...
January 2017: Science Advances
T Karthick, Poonam Tandon, Swapnil Singh
Tretinoin is known to be a pharmaceutical drug for treating acne vulgaris, keratosis pilaris, and acute promyelocytic leukemia. In order to reveal the possible conformers of tretinoin, the energies of all the conformers through rotational bonds have been evaluated by systematic rotor search analysis. The intramolecular interactions ranging from strong hydrogen bonds to weak van der Waals forces present in tretinoin have been distinguished with the help of electron density mapping and wavefunction analysis. The global reactivity descriptors and Fukui functions of tretinoin have been calculated and discussed...
2017: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
Renu Geetha Bai, Kasturi Muthoosamy, Fiona Natalia Shipton, Sivakumar Manickam
Graphene is one of the highly explored nanomaterials due to its unique and extraordinary properties. In this study, by utilizing a hydrothermal reduction method, graphene oxide (GO) was successfully converted to reduced graphene oxide (RGO) without using any toxic reducing agents. Following this, with the use of ultrasonic cavitation, profoundly stable few layer thick RGO nanodispersion was generated without employing any stabilizers or surfactants. During ultrasonication, shockwaves from the collapse of bubbles cause a higher dispersing energy to the graphene nanosheets which surpass the forces of Van der Waal's and π-π stacking and thus pave the way to form a stable aqueous nanodispersion of graphene...
May 2017: Ultrasonics Sonochemistry
Yan-Yue Lou, Kai-Li Zhou, Dong-Qi Pan, Jia-Le Shen, Jie-Hua Shi
Clonazepam, a type of benzodiazepine, is a classical drug used to prevent and treat seizures, panic disorder, movement disorder, among others. For further clarifying the distribution of clonazepam in vivo and the pharmacodynamic and pharmacokinetic mechanisms, the binding interaction between clonazepam and bovine serum albumin (BSA) was investigated using ultraviolet spectroscopy (UV), steady-state fluorescence spectroscopy, synchronous fluorescence spectroscopy, three-dimensional (3D) fluorescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and molecular docking methods...
December 24, 2016: Journal of Photochemistry and Photobiology. B, Biology
Aaron W Chen, Bing Fang, Hyunbok Lee, Alejandro L Briseno, Maria M Santore
This study addresses the electrostatic and van der Waals interactions at the aqueous interface of large area CVD graphene, 1-3 layers thick on a silica support and assessed by Raman spectroscopy to have exclusive sp2 character. Ionic strength was found to substantially alter the interactions of silica microspheres with silica-supported graphene. Particles were nonadhesive at large Debye lengths but became irreversibly adherent at reduced Debye lengths about 2nm or less. This was demonstrated to be qualitatively parallel to the influence of ionic strength on silica-silica interactions...
December 2, 2016: Journal of Colloid and Interface Science
Honglei Wang, Jin Shi, Guokui Liu, Yongqin Zhang, Jingjing Zhang, Shenmin Li
Molecular dynamics simulations were used to investigate the transport properties of water-methanol solutions getting through the carbon nanotube (CNT) with an oscillating electric field. Eight alternating electric fields with different oscillation periods were used in this work. Under the oscillating electric field, water molecules have the advantage of occupying CNT over methanol molecules. Meanwhile, the space occupancy of water-methanol solution in the CNT increases with the increasing of oscillating period...
January 9, 2017: Journal of Physical Chemistry. B
Zhengyang Gao, Yi Ding, Weijie Yang, Wentao Han
High moisture content is a main characteristic of low-rank coal, such as lignite. Numerous oxygen containing functional groups in lignite make it represent some special properties, and these functional groups affect the adsorption mechanisms of water molecules on lignite surface. This study reports some typical water · · · lignite conformations, along with a detailed analysis of the geometry, electrostatic potential distribution, reduced density gradient of interaction, and interaction energy decomposition...
January 2017: Journal of Molecular Modeling
Donglin Li, Yonggang Yang, Chaozheng Li, Yufang Liu
The dispersion-corrected density functional theory (DFT-D3) is used to investigate the mechanism of mesoporous pulp waste (MPW) and polyaniline (PANI) adsorptive removal methyl orange (MO) dye from their aqueous solutions. The results are absolutely reliable because of the sufficiently accurate method although such big systems are studied. It is demonstrated that hydrogen bond and Van Der Waals interactions play a significant role in MO adsorption by MPW and PANI. For MO adsorption by MPW, hydrogen bond and Van Der Waals interactions are both weakened in S1 state...
January 5, 2017: Environmental Research
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