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Hai Qian, Susnata Pramanik, Ivan Aprahamian
A family of easily accessible light-activated hydrazone switches has been developed having thermal half-lives of up to 2700 years! Structure-property analysis shows that replacing the rotor pyridyl group of our typical hydrazone switch with a phenyl one leads to the long-live negative photochromic compounds. The switching properties of the hydrazones in both toluene and DMSO were assessed offering insights into the kinetics and thermodynamics of the switching process.
June 23, 2017: Journal of the American Chemical Society
Hai Yu, Sebastian Engel, Gábor Janiga, Dominique Thévenin
Flow-induced hemolysis is a crucial issue for many biomedical applications; in particular, it is an essential issue for the development of blood-transporting devices such as left ventricular assist devices, and other types of blood pumps. In order to estimate red blood cell (RBC) damage in blood flows, many models have been proposed in the past. Most models have been validated by their respective authors. However, the accuracy and the validity range of these models remains unclear. In this work, the most established hemolysis models compatible with computational fluid dynamics of full-scale devices are described and assessed by comparing two selected reference experiments: a simple rheometric flow and a more complex hemodialytic flow through a needle...
June 23, 2017: Artificial Organs
Mohammed Saeed, Hakan Oral
No abstract text is available yet for this article.
June 16, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
Jos C M Kistemaker, Peter Stacko, Diederik Roke, Alexander Thomas Wolters, G Henrieke Heideman, Mu-Chieh Chang, Pieter van der Meulen, Johan Visser, Edwin Otten, Ben L Feringa
Symmetric molecular motors based on two overcrowded alkenes with a notable absence of a stereogenic center show potential to function as novel mechanical systems in the development of more advanced nanomachines and controlled motion over surfaces. Elucidation of the key parameters and limitations of these third generation motors is essential for the design of optimized molecular machines based on light-driven rotary motion. Herein we demonstrate the thermal and photochemical rotational behavior of a series of third generation light-driven molecular motors...
June 19, 2017: Journal of the American Chemical Society
Eun A Kim, Joseph Panushka, Trevor Meyer, Nicholas Ide, Ryan Carlisle, Samantha Baker, David F Blair
Direction switching in the flagellar motor of Escherichia coli is under the control of a complex on the rotor formed from the proteins FliG, FliM, and FliN. FliG lies at the top of the switch complex (i.e., nearest the membrane) and is arranged with its C-terminal domain (FliGC) resting on the middle domain (FliGM) of the neighboring subunit. This organization requires the protein to adopt an open conformation that exposes the surfaces engaging in inter-subunit FliGC/FliGM contacts. In a recent study, Baker and coworkers [Nat...
June 15, 2017: Journal of Molecular Biology
Markéta Kubánková, Ismael López-Duarte, James A Bull, Devkee M Vadukul, Louise C Serpell, Marie de Saint Victor, Eleanor Stride, Marina K Kuimova
Changes in microscopic viscosity and macromolecular crowding accompany the transition of proteins from their monomeric forms into highly organised fibrillar states. Previously, we have demonstrated that viscosity sensitive fluorophores termed 'molecular rotors', when freely mixed with monomers of interest, are able to report on changes in microrheology accompanying amyloid formation, and measured an increase in rigidity of approximately three orders of magnitude during aggregation of lysozyme and insulin. Here we extend this strategy by covalently attaching molecular rotors to several proteins capable of assembly into fibrils, namely lysozyme, fibrinogen and amyloid-β peptide (Aβ(1-42))...
September 2017: Biomaterials
Cuiping Chen, William R Folk, Rodrigo Lazo-Portugal, Thomas M Finn, Martha Knight
Spiral countercurrent-chromatography has great potential for improving the capacity and efficiency of purification of secondary metabolites, and here we describe applications useful for the isolation of flavonoids from the widely used South African medicinal plant, Sutherlandia frutescens (L.) R. Br. In the spiral tubing support rotor, STS-4 for high-speed counter-current chromatography, several polar butanol aqueous solvent systems were selected using a logK plot, and the novel flavonol glycosides (sutherlandins A-D) were well separated by the optimized solvent system (ethyl acetate:n-butanol:acetic acid:water; 5:1:0...
July 28, 2017: Journal of Chromatography. A
Navin Khaneja, Ashutosh Kumar
The paper describes a family of novel recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, called two pulse recoupling. These pulse sequences can be employed for both homonuclear and heteronuclear recoupling experiments and are robust to dispersion in chemical shifts and rf-inhomogeneity. The homonuclear pulse sequence consists of a building block (π)ϕ(π)-ϕ where ϕ=π4n, and n is number of blocks in a rotor period. The recoupling block is made robust to rf-inhomogeneity by extending it to (π)ϕ(π)-ϕ(π)π+ϕ(π)π-ϕ...
June 12, 2017: Journal of Magnetic Resonance
Massimo Mella, Emanuele Curotto
Despite the fact that the \emph{para}--hydrogen molecule ($p$--H$_2$) and its isotopomers ($o$--D$_2$ and $p$--T$_2$) are commonly modelled as spherical objects due to the large separation between rotational states, there may be situations (\emph{e.g.} adsorption in pores and on surfaces) in which such an approximation neglects important degrees of freedom (\emph{i.e.} the rotational ones) and introduces uncontrolled biases in the predicted properties. To better understand when approximating such molecules as spheres introduces shortcomings in their representation, we employed diffusion Monte Carlo to simulate small/medium--sized molecular aggregates, either isolated in space or experiencing external model potentials, to compute energetic quantities and distribution functions...
June 15, 2017: Journal of Physical Chemistry. A
Alessia Marruzzo, Payal Tyagi, Fabrizio Antenucci, Andrea Pagnani, Luca Leuzzi
The inverse problem is studied in multi-body systems with nonlinear dynamics representing, e.g., phase-locked wave systems, standard multimode and random lasers. Using a general model for four-body interacting complex-valued variables we test two methods based on pseudolikelihood, respectively with regularization and with decimation, to determine the coupling constants from sets of measured configurations. We test statistical inference predictions for increasing number of sampled configurations and for an externally tunable temperature-like parameter mimicing real data noise and helping minimization procedures...
June 14, 2017: Scientific Reports
Dennis H Lau, Dominik Linz, Ulrich Schotten, Rajiv Mahajan, Prashanthan Sanders, Jonathan M Kalman
Recent advances in our understanding of the mechanisms underlying atrial fibrillation (AF) have further underscored the complex pathophysiological basis of the arrhythmia. It has become apparent that the current clinical classification of AF does not reflect the severity of the underlying atrial disease. Atrial fibrosis has been identified as the key structural change in different substrates that are responsible for the perpetuation of AF. Three-dimensional electroanatomical mapping and late gadolinium-enhanced magnetic resonance imaging are novel modalities that can be used to facilitate identification and quantitation of atrial fibrosis for improved delineation of the AF substrate...
May 24, 2017: Heart, Lung & Circulation
Branko Zajamsek, Con J Doolan, Danielle J Moreau, Jeoffrey Fischer, Zebb Prime
Trailing edge noise from stationary and rotating NACA 0012 airfoils is characterised and compared with a noise prediction based on the semi-empirical Brooks, Pope, and Marcolini (BPM) model. The NACA 0012 is symmetrical airfoil with no camber and 12% thickness to chord length ratio. Acoustic measurements were conducted in an anechoic wind tunnel using a stationary NACA 0012 airfoil at 0° pitch angle. Airfoil self-noise emissions from rotating NACA 0012 airfoils mounted at 0° and 10° pitch angles on a rotor-rig are studied in an anechoic room...
May 2017: Journal of the Acoustical Society of America
Junaid A B Zaman, Tina Baykaner, Paul Clopton, Vijay Swarup, Robert C Kowal, James P Daubert, John D Day, John Hummel, Amir A Schricker, David E Krummen, Moussa Mansour, Gery F Tomassoni, Kevin R Wheelan, Mohan Vishwanathan, Shirley Park, Paul J Wang, Sanjiv M Narayan, John M Miller
INTRODUCTION: The role of atrial fibrillation (AF) substrates is unclear in patients with paroxysmal AF (PAF) that recurs after pulmonary vein isolation (PVI). We hypothesized that patients with recurrent post-ablation (redo) PAF despite PVI have electrical substrates marked by rotors and focal sources, and structural substrates that resemble persistent AF more than patients with (de novo) PAF at first ablation. METHODS: In 175 patients at 11 centers, we compared AF substrates in both atria using 64 pole-basket catheters and phase mapping, and indices of anatomical remodeling between patients with de novo or redo PAF and first ablation for persistent AF...
April 2017: JACC. Clinical Electrophysiology
Lingling Wang, Guo Huan, Roya Momen, Alireza Azizi, Tianlv Xu, Steven R Kirk, Michael Filatov, Samantha Jenkins
A quantum theory of atoms in molecules (QTAIM) and stress tensor analysis was applied to analyze intramolecular interactions influencing the photoisomerization dynamics of a light-driven rotary molecular motor. For selected nonadiabatic molecular dynamics trajectories characterized by markedly different S1 state lifetimes, the electron densities were obtained using the ensemble density functional theory method. The analysis revealed that torsional motion of the molecular motor blades from the Franck-Condon point to the S1 energy minimum and the S1/S0 conical intersection is controlled by two factors: greater numbers of intramolecular bonds before the hop-time and unusually strongly coupled bonds between the atoms of the rotor and the stator blades...
June 14, 2017: Journal of Physical Chemistry. A
Wang Li, Chun-Ting He, Ying Zeng, Cheng-Min Ji, Zi-Yi Du, Wei-Xiong Zhang, Xiao-Ming Chen
A new strategy for the construction of crystalline molecular rotors is presented. The combination of a conformation-modifiable macrocyclic host and two cooperative guests affords one supramolecular gyroscope-like compound, (t-BuNH3)(18-crown-6)[ZnCl3(H2O)], in which the coordinated water molecule functions as an ultrasmall polar rotator, revealed by its significant dielectric relaxation and the molecular dynamics simulations. In addition, such a compound can reversibly undergo a polar-to-polar phase transition triggered by the changed conformation of the 18-crown-6 host, leading to a switchable on/off rotation of water molecule, well controlled by strength and direction of charge-assisted hydrogen bonds...
June 21, 2017: Journal of the American Chemical Society
Alexander Semenov, Dmitri A Babikov
A mixed quantum/classical theory for inelastic collision of two asymmetric-top rotor molecules is developed. In this method the quantum state-to-state transitions between the rotational states of molecules (internal) are treated quantum mechanically using time-dependent Schrodinger equation, whereas their relative translational motion (responsible for scattering) is treated classically, using the average trajectory approach. Two versions of the formula for transition matrix elements are presented: a straightforward approach that uses numerical multi-dimensional quadrature over all the internal degrees of freedom, and a more standard analytic approach that uses expansion of the PES over the basis set of spherical harmonics...
June 5, 2017: Journal of Physical Chemistry. A
Peter S Sherin, Ismael López-Duarte, Michael R Dent, Markéta Kubánková, Aurimas Vyšniauskas, James A Bull, Evdokiya S Reshetnikova, Andrey S Klymchenko, Yuri P Tsentalovich, Marina K Kuimova
The plasma membranes of cells within the eye lens play an important role in metabolite transport within the avascular tissue of the lens, maintaining its transparency over the entire lifespan of an individual. Here we use viscosity-sensitive 'molecular rotors' to map the microscopic viscosity within these unusual cell membranes, establishing that they are characterised by an unprecedentedly high degree of lipid organisation.
May 1, 2017: Chemical Science
Wenjie Zhou, Xuesong Wei, Leqin Wang, Guangkuan Wu
Solving the static equilibrium position is one of the most important parts of dynamic coefficients calculation and further coupled calculation of rotor system. The main contribution of this study is testing the superlinear iteration convergence method-twofold secant method, for the determination of the static equilibrium position of journal bearing with finite length. Essentially, the Reynolds equation for stable motion is solved by the finite difference method and the inner pressure is obtained by the successive over-relaxation iterative method reinforced by the compound Simpson quadrature formula...
May 2017: Royal Society Open Science
Yaxi Hu, Shuo Wang, Shenlin Wang, Xiaonan Lu
Carcinogenic Sudan I has been added illegally into spices for an apparent freshness. (1)H solution and solid-state (SS) nuclear magnetic resonance (NMR) spectroscopies were applied and compared for determination of Sudan I in paprika powders (PPs). For solution NMR, PPs spiked with Sudan I were extracted with acetonitrile, centrifuged, rotor-evaporated, and re-dissolved in DMSO-d6 for spectral collection. For SSNMR, Sudan I contaminated PPs were mixed with DMSO-d6 solution and used for spectral collection. Linear regression models constructed for quantitative analyses resulted in the average accuracies for unknown samples as 98% and 105%, respectively...
June 1, 2017: Scientific Reports
Peter Štacko, Jos C M Kistemaker, Thomas van Leeuwen, Mu-Chieh Chang, Edwin Otten, Ben L Feringa
Biological molecular motors translate their local directional motion into ordered movement of other parts of the system to empower controlled mechanical functions. The design of analogous geared systems that couple motion in a directional manner, which is pivotal for molecular machinery operating at the nanoscale, remains highly challenging. Here, we report a molecular rotary motor that translates light-driven unidirectional rotary motion to controlled movement of a connected biaryl rotor. Achieving coupled motion of the distinct parts of this multicomponent mechanical system required precise control of multiple kinetic barriers for isomerization and synchronous motion, resulting in sliding and rotation during a full rotary cycle, with the motor always facing the same face of the rotor...
June 2, 2017: Science
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