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Van der Waals

Neha Maurya, Mehraj Ud Din Parray, Jitendra Kumar Maurya, Amit Kumar, Rajan Patel
The binding nature of amphiphilic drugs viz. promethazine hydrochloride (PMT) and adiphenine hydrochloride (ADP), with human hemoglobin (Hb) was unraveled by fluorescence, absorbance, time resolved fluorescence, fluorescence resonance energy transfer (FRET) and circular dichroism (CD) spectral techniques in combination with molecular docking and molecular dynamic simulation methods. The steady state fluorescence spectra indicated that both PMT and ADP quenches the fluorescence of Hb through static quenching mechanism which was further confirmed by time resolved fluorescence spectra...
March 11, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Jong Wha Lee, Hyun Hee L Lee, Kimberly L Davidson, Matthew F Bush, Hugh I Kim
The investigation of ion structures based on a combination of ion mobility mass spectrometry (IM-MS) experiments and theoretical collision cross section (CCS) calculations has become important to many fields of research. However, the accuracy of current CCS calculations for ions in nitrogen drift gas limits the information content of many experiments. In particular, few studies have evaluated and attempted to improve the theoretical tools for CCS calculation in nitrogen drift gas. In this study, based on high-quality experimental measurements and theoretical modeling, a comprehensive evaluation of various aspects of CCS calculations in nitrogen drift gas is performed...
March 21, 2018: Analyst
Mengmeng Li, Ying Dai, Wei Wei, Baibiao Huang
Developing two-dimensional (2D) photocatalysts based on traditional layered materials provides new opportunities for photocatalytic applications. However, unlike van der Waals layered structures, the recently synthesized Bi2WO6 monolayer with unsaturated atoms showed more diverse photocatalytic performances. Here, a systematic study about the electronic and photocatalytic properties of monolayer, double-layer and bulk phase (MP, DP and BP) Bi2WO6 was carried out with first-principles calculations to disclose the origin of the superior photocatalytic activities of 2D Bi2WO6...
March 21, 2018: Physical Chemistry Chemical Physics: PCCP
Tomohiko Hayashi, Tomoaki Matsuda, Takashi Nagata, Masato Katahira, Masahiro Kinoshita
We investigate the RBD1-r(GUAGU) binding as a case study using all-atom models for the biomolecules, molecular models for water, and the currently most reliable statistical-mechanical method. RBD1 is one of the RNA-binding domains of mammalian Musashi1 (Msi1), and r(GUAGU) contains the minimum recognition sequence for Msi1, r(GUAG). We show that the binding is driven by a large gain of configurational entropy of water in the entire system. It is larger than the sum of conformational-entropy losses for RBD1 and r(GUAGU)...
March 21, 2018: Physical Chemistry Chemical Physics: PCCP
Matthias Florian, Malte Hartmann, Alexander Steinhoff, Julian Klein, Alexander W Holleitner, Jonathan J Finley, Tim Oliver Wehling, Michael Kaniber, Christopher Gies
The electronic and optical properties of monolayer transition-metal dichalcogenides (TMDs) and van der Waals heterostructures are strongly subject to their dielectric environment. In each layer the field lines of the Coulomb interaction are screened by the adjacent material, which reduces the single-particle band gap as well as exciton and trion binding energies. By combining an electrostatic model for a dielectric hetero-multi-layered environment with semiconductor many-particle methods, we demonstrate that the electronic and optical properties are sensitive to the interlayer distances on the atomic scale...
March 20, 2018: Nano Letters
Anomitra Dey, Aditya Kamat, Sonal Nayak, Dganit Danino, Ellina Kesselman, Prajakta Dandekar, Ratnesh Jain
Researchers have explored the ability of chitosan to form nanoparticles, to suit varying applications, ranging from wound-healing to gene delivery. Ionic gelation is a widely used method for formulating chitosan nanoparticles, where self-assembly plays a crucial role. This self-assembly is initially promoted by hydrophilic-hydrophobic parity amongst individual chitosan residues, along with electrostatic and Van der Waals interactions with the cross-linker. However, until now the intrinsic ability of chitosan to self-assemble is not widely studied; hence, we investigate the self-assembly of chitosan, based on proton balance between its protonated and deprotonated residues, to promote facile nanoparticle synthesis...
March 14, 2018: Colloids and Surfaces. B, Biointerfaces
Hao Li, Ming Li, Zhan Kang
The competition between the out-of-plane rigidity and the van der Waals interaction leads to the scrolled and folded structural configurations of graphene. These configuration changes, as compared with the initially planar geometry, significantly affect the electronic, optical and mechanical properties of graphene, promising exciting applications in graphene-nanoelectronics. We propose a finite-deformation theoretical model, in which no presumed assumptions on the geometries of deformed configurations are required...
March 20, 2018: Nanotechnology
Suji Gim, Hyung-Kyu Lim, Hyungjun Kim
The solid-liquid interface is of great interest because of its highly heterogeneous character and its ubiquity in various applications. The most fundamental physical variable determining the strength of the solid-liquid interface is the solid-liquid interfacial tension, which is usually measured according to the contact angle. However, an accurate experimental measurement and a reliable theoretical prediction of the contact angle remain lacking because of many practical issues. Here, we propose a first principles-based simulation approach to quantitatively predict the contact angle of an ideally clean surface using our recently developed multiscale simulation method of density functional theory in classical explicit solvents (DFT-CES)...
March 20, 2018: Journal of Physical Chemistry Letters
Marek E Schmidt, Ahmed M M Hammam, Takuya Iwasaki, Teruhisa Kanzaki, Manoharan Muruganathan, Shinichi Ogawa, Hiroshi Mizuta
Carbon nanoscrolls (CNS) with their open ended morphology have recently attracted interest due to the potential application in gas capture, biosensors and interconnects. However, CNS currently suffer from the same issue that have hindered widespread integration of CNTs in sensors and devices: Formation is done ex-situ, and the tubes have to be placed with precision and reliability - a difficult task with low yield. Here, we demonstrate controlled in-situ formation of electrically contacted CNS from suspended graphene nanoribbons (GNRs) with slight tensile stress...
March 20, 2018: Nanotechnology
Shweta D Dabhi, Basant Roondhe, Prafulla K Jha
Understanding the interactions between biomolecules and boron nitride nanostructures is key for their use in nanobiotechnology and medical engineering. In this study, we investigated the adsorption of nucleobases adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U) over armchair and zigzag boron nitride nanoribbons (BNNR) using density functional theory to define the applicability of BNNR for the sensing of nucleobases and DNA sequencing. To appropriately account for dispersion, the van der Waals forces (DFT-D2)-type method developed by Grimme was also included in the calculations...
March 20, 2018: Physical Chemistry Chemical Physics: PCCP
Eugenio Zallo, Stefano Cecchi, Jos E Boschker, Antonio M Mio, Fabrizio Arciprete, Stefania Privitera, Raffaella Calarco
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
March 19, 2018: Scientific Reports
Nils M Freitag, Tobias Reisch, Larisa A Chizhova, Péter Nemes-Incze, Christian Holl, Colin R Woods, Roman V Gorbachev, Yang Cao, Andre K Geim, Kostya S Novoselov, Joachim Burgdörfer, Florian Libisch, Markus Morgenstern
Coherent manipulation of the binary degrees of freedom is at the heart of modern quantum technologies. Graphene offers two binary degrees: the electron spin and the valley. Efficient spin control has been demonstrated in many solid-state systems, whereas exploitation of the valley has only recently been started, albeit without control at the single-electron level. Here, we show that van der Waals stacking of graphene onto hexagonal boron nitride offers a natural platform for valley control. We use a graphene quantum dot induced by the tip of a scanning tunnelling microscope and demonstrate valley splitting that is tunable from -5 to +10 meV (including valley inversion) by sub-10-nm displacements of the quantum dot position...
March 19, 2018: Nature Nanotechnology
S Hu, K Gopinadhan, A Rakowski, M Neek-Amal, T Heine, I V Grigorieva, S J Haigh, F M Peeters, A K Geim, M Lozada-Hidalgo
Atoms start behaving as waves rather than classical particles if confined in spaces commensurate with their de Broglie wavelength. At room temperature this length is only about one ångström even for the lightest atom, hydrogen. This restricts quantum-confinement phenomena for atomic species to the realm of very low temperatures1-5 . Here, we show that van der Waals gaps between atomic planes of layered crystals provide ångström-size channels that make quantum confinement of protons apparent even at room temperature...
March 19, 2018: Nature Nanotechnology
Marshall Slemrod
This paper addresses the main issue of Hilbert's sixth problem, namely the rigorous passage of solutions to the mesoscopic Boltzmann equation to macroscopic solutions of the Euler equations of compressible gas dynamics. The results of the paper are that (i) in general Hilbert's program will fail because of the appearance of van der Waals-Korteweg capillarity terms in a macroscopic description of motion of a gas, and (ii) the van der Waals-Korteweg theory itself might satisfy Hilbert's quest for a map from the 'atomistic view' to the laws of motion of continua...
April 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
C Binot, C-H Chouard
The existence of an information vector common to very different pathologies is the hypothesis of one of us, the argumentation and discussion of which we present here. It is a mesomorphic state of material called liquid crystal. The liquid-ordered (Lo) phase, made up of membrane rafts mediated by cholesterol, lies at the center of our concept. This mesophase is either preexistent and then modified by the pathogenic process, or initiated by the latter. The most notable disorders involved are Alzheimer's, Parkinson's, Charcot and Creutzfeldt-Jakob diseases, flu-like illnesses and acquired immunodeficiency syndrome (AIDS), although this list may well be extended to include other anisotropic, birefringent amyloid proteinopathies, which have properties compatible with those of liquid crystals...
March 16, 2018: Revue Neurologique
Sankaran Sundaresan, Ali Ozel, Jari Kolehmainen
As multiscale structures are inherent in multiphase flows, constitutive models employed in conjunction with transport equations for momentum, species, and energy are scale dependent. We suggest that this scale dependency can be better quantified through deep learning techniques and formulation of transport equations for additional quantities such as drift velocity and analogies for species, energy, and momentum transfer. How one should incorporate interparticle forces, which arise through van der Waals interaction, dynamic liquid bridges between wet particles, and tribocharging, in multiscale models warrants further study...
March 19, 2018: Annual Review of Chemical and Biomolecular Engineering
Katarina Ulicna, Zuzana Bednarikova, Wei-Tse Hsu, Martina Holztragerova, Josephine W Wu, Slavka Hamulakova, Steven S-S Wang, Zuzana Gazova
Amyloid aggregates of proteins are one of the most abundant and important naturally occurring self-associated assemblies. Formation of poly/peptide amyloid aggregates is also associated with the widely spread diseases, so called amyloidosis, which include Alzheimer's disease, diabetes mellitus and lysozyme amyloidosis. These disorders are still incurable and novel therapeutical approaches are focused on using small molecules for inhibition of amyloid aggregation. We have observed effect of three structurally distinct groups of tacrine/acridone - coumarin heterodimers on hen egg white (HEW) lysozyme fibrillization in vitro...
March 9, 2018: Colloids and Surfaces. B, Biointerfaces
Xingjia Guo, Jie Yao, Xuehui Liu, Hongyan Wang, Lizhi Zhang, Liping Xu, Aijun Hao
Eu3+ doped LaPO4 fluorescent nanorods (LaPO4 :Eu) was successfully fabricated by a hydrothermal process. The obtained LaPO4 :Eu nanorods under the optimal conditions were characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD) technique, Fourier transform infrared (FTIR), UV-vis absorption and fluorescence spectroscopy. The nanorods with a length of 50-100nm and a diameter of about 10nm, can emit strong red fluorescence upon excitation at 241nm. The FTIR result confirmed that there are lots of phosphate groups on the surfaces of nanorods...
March 6, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Qi Gao, Chao Lu, Xiao-Wen Wang, Jun-Wei Zhang, Youtao Song, You-Lin Xue
Irisin is found closely associated with promoting the browning of beige fat cells in white adipose tissue. The crystal structure reveals that irisin forms a continuous inter-subunit β-sheet dimer. Here, molecular dynamics (MD) simulation and steered molecular dynamics (SMD) simulation were performed to investigate the dissociation process and the intricate interactions between the two irisin monomers. In the process of MD, the interactions between the monomers were roughly analyzed through the average numbers of both hydrophobic contacts and H-bonds...
March 16, 2018: Journal of Molecular Modeling
V Sofonea, T Biciuşcă, S Busuioc, Victor E Ambruş, G Gonnella, A Lamura
Aiming to study the bubble cavitation problem in quiescent and sheared liquids, a third-order isothermal lattice Boltzmann model that describes a two-dimensional (2D) fluid obeying the van der Waals equation of state, is introduced. The evolution equations for the distribution functions in this off-lattice model with 16 velocities are solved using the corner-transport-upwind (CTU) numerical scheme on large square lattices (up to 6144×6144 nodes). The numerical viscosity and the regularization of the model are discussed for first- and second-order CTU schemes finding that the latter choice allows to obtain a very accurate phase diagram of a nonideal fluid...
February 2018: Physical Review. E
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