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Taraknath Mandal, Ronald G Larson
Using fully atomistic and coarse-grained (CG) molecular dynamics (MD) simulations, we report, for the first time, the self-assembly of initially randomly dispersed dodecyl-β-d-maltoside (DDM) surfactants into a striped cylindrical micelle (SCM) with lamellae of surfactant heads and tails alternating along the cylindrical axis, with both heads and tails in contact with the water. By changing the interaction strength of the head group with water relative to itself, we find that such micelles are most likely for head groups with marginal solubility in the water solvent...
March 22, 2018: Soft Matter
Jianchang Xu, Shuangqing Sun, Zhikun Wang, Shiyuan Peng, Songqing Hu, Lijuan Zhang
Dissipative particle dynamics (DPD) simulation is used to study the effect of pH on the morphological transition in micelles assembled from dirhamnolipids (diRLs), and analyze the pH-driven mechanism and influence factors of micellar surface patterns. At pH < 4.0, various multilayer structures with homogeneous surface patterns are observed, whereas diRLs can self-assemble into novel anisotropic morphologies with phase-separated surface patterns at pH > 7.4, such as patchy spherical micelles, rod-like micelles with helical surface patterns and a lamellar phase with anisotropic surface patterns...
March 22, 2018: Physical Chemistry Chemical Physics: PCCP
Tuan Anh Ho, Yifeng Wang, Louise J Criscenti
Kerogen plays a central role in hydrocarbon generation in an oil/gas reservoir. In a subsurface environment, kerogen is constantly subjected to stress confinement or relaxation. The interplay between mechanical deformation and gas adsorption of the materials could be an important process for shale gas production but unfortunately is poorly understood. Using a hybrid Monte Carlo/molecular dynamics simulation, we show here that a strong chemo-mechanical coupling may exist between gas adsorption and mechanical strain of a kerogen matrix...
March 22, 2018: Physical Chemistry Chemical Physics: PCCP
Neeladri Sekhar Roy, Subrata Debnath, Abhijit Chakraborty, Prasenjit Chakraborty, Indrani Bera, Raka Ghosh, Nanda Ghoshal, Saikat Chakrabarti, Siddhartha Roy
Localized separation of strands of duplex DNA is a necessary step in many DNA-dependent processes, including transcription and replication. Little is known about how these strand separations occur. The strand-separated E.coli RNA polymerase-promoter open-complex structure showed four bases of the non-template strand, the master base -11A, -7, -6 and +2, in a flipped state and inserted into protein pockets. To explore whether any property of these bases in the duplex state pre-disposes them to flipping, NMR studies were performed on a wild-type promoter in the duplex state...
March 22, 2018: Physical Chemistry Chemical Physics: PCCP
Evgeniya V Kaigorodova, Olga E Savelieva, Liubov A Tashireva, Natalia A Tarabanovskaya, Elena I Simolina, Evgeny V Denisov, Elena M Slonimskaya, Evgeny L Choynzonov, Vladimir M Perelmuter
The biological properties of circulating tumor cells (CTCs), and their dynamics during neoadjuvant chemotherapy are important, both for disease progression prediction and therapeutic target determination, with the aim of preventing disease progression. The aim of our study was to estimate of different CTC subsets in breast cancer during the NACT (neoadjuvant chemotherapy). The prospective study includes 27 patients with invasive breast cancer, T2-4N0-3M0, aged 32 to 60 years. Venous heparinized blood samples, taken before and after biopsy, after each courses of chemotherapy (on days 3-7), and before surgical intervention, served as the material for this study...
March 22, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Qiujing Dong, Chunhua Luo, Na Li, Jiaxiang Chi, Qingqing Zhang
A series of copolymers with an adamantyl side group (poly(NIPAM-co-AdMA) and poly(DMAM-co-AdMA)) were prepared by radical copolymerization of N -isopropylacrylamide (NIPAM) and N , N -dimethylacrylamide (DMAM) with a 2-methyl-2-adamantylmethacrylate (AdMA) monomer. The structure and composition of the as-synthesized copolymers were characterized by Fourier transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance (¹H NMR) spectroscopy, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and elemental analysis...
March 22, 2018: Materials
Xiaofeng Niu, Shidong Feng, Shaopeng Pan
Structural defects were investigated by a recently proposed structural parameter, quasi-nearest atom (QNA), in a modeled Zr50 Cu50 metallic glass through molecular dynamics simulations. More QNAs around an atom usually means that more defects are located near the atom. Structural analysis reveals that the spatial distribution of the numbers of QNAs displays to be clearly heterogeneous. Furthermore, QNA is closely correlated with cluster connections, especially four-atom cluster connections. Atoms with larger coordination numbers usually have less QNAs...
March 22, 2018: Materials
Yah Yun Aw, Cheow Keat Yeoh, Muhammad Asri Idris, Pei Leng Teh, Khairul Amali Hamzah, Shulizawati Aqzna Sazali
Fused deposition modelling (FDM) has been widely used in medical appliances, automobile, aircraft and aerospace, household appliances, toys, and many other fields. The ease of processing, low cost and high flexibility of FDM technique are strong advantages compared to other techniques for thermoelectric polymer composite fabrication. This research work focuses on the effect of two crucial printing parameters (infill density and printing pattern) on the tensile, dynamic mechanical, and thermoelectric properties of conductive acrylonitrile butadiene styrene/zinc oxide (CABS/ZnO composites fabricated by FDM technique...
March 22, 2018: Materials
Peter A Muller, Jennifer L Mueller, Michelle Mellenthin, Rashmi Murthy, Michael Capps, Brandie Wagner, Melody Alsaker, Robin Deterding, Scott D Sagel, Jordana Hoppe
Lung function monitoring by spiromety plays a critical role in the clinical care of pediatric cystic fibrosis (CF) patients, but many young children are unable to perform spirometry, and the outputs are often normal even in the presence of lung disease. Measures derived from electrical impedance tomography (EIT) images were studied for their utility as potential surrogates for spirometry in CF patients and to assess response to intravenous antibiotic treatment for acute pulmonary exacerbations (PEx) in a subset of patients...
March 22, 2018: Physiological Measurement
Melissa Preissner, Rhiannon P Murrie, Isaac Pinar, Freda Werdiger, Richard P Carnibella, Graeme R Zosky, Andreas Fouras, Stephen Dubsky
We have developed an X-ray imaging system for &lt;i&gt;in vivo&lt;/i&gt; four-dimensional computed tomography (4DCT) of small animals for pre-clinical lung investigations. Our customized laboratory facility is capable of high resolution &lt;i&gt;in vivo&lt;/i&gt; imaging at high frame rates. Characterization using phantoms demonstrate a spatial resolution of slightly below 50 μm at imaging rates of 30 Hz, and the ability to quantify material density differences of at least 3%...
March 22, 2018: Physics in Medicine and Biology
A Shore-Maggio, G S Aeby, S M Callahan
Environmental cofactors alter host-pathogen interactions and influence disease dynamics by impairing host resistance and/or increasing pathogen virulence. Terrestrial runoff is recognized as a major threat to coral reef health. However, the direct links between runoff and coral disease are not clear. Montipora white syndrome (MWS) is a coral disease that occurs in the Hawaiian archipelago, can be caused by various bacterial pathogens, including Vibrio species, and is linked to conditions associated with heavy rainfall and runoff...
March 22, 2018: Diseases of Aquatic Organisms
Seyed Mohammad Taghdisi, Noor Mohammad Danesh, Mohammad Ramezani, Ahmad Sarreshtehdar Emrani, Khalil Abnous
Zearalenone (ZEN) toxicity is a significant risk for human beings. Thus, it is of high importance to develop sensitive, precise and inexpensive analytical methods for ZEN detection, especially in human serum. Here, a colorimetric aptasensor is presented for determination of ZEN based on nontarget-induced aptamer walker, catalytic reaction of gold nanoparticles (AuNPs), exonuclease III (Exo III) as signal amplifier and 4-nitrophenol as colorimetric agent. Low amount of ZEN requirement and signal amplification are some of the distinct advantages of the proposed aptasensor...
March 22, 2018: ACS Applied Materials & Interfaces
Daniel Bonhenry, François Dehez, Mounir Tarek
The low bioavailability of most therapeutic compounds is often counterbalanced by association with molecular vectors capable of crossing cell membranes. Previous studies demonstrated that for vectors bearing titratable chemical groups, the translocation process might be accompanied by a change in the protonation state. For simple compounds e.g. a lysine analog, free energy calculations, using a single collective variable, namely the insertion depth, suggest that such a transition could only take place if the amino acid diffuses deep enough into the hydrophobic core of the membrane, a situation thermodynamically unfavorable...
March 22, 2018: Physical Chemistry Chemical Physics: PCCP
Konda Reddy Karnati, Yixuan Wang
Two widely used anticancer drugs, doxorubicin (DOX) and paclitaxel (PTX), possess distinct physical properties and chemotherapy specificity. In order to investigate their interaction mechanism with single-walled carbon nanotubes (SWCNTs), co-loading and releasing from the SWCNTs, all-atom molecular dynamics (MD) simulations were firstly carried out for different SWCNT systems, followed by binding free energy calculation with MM-PBSA. The results indicate that the co-loading of DOX and PTX onto the pristine SWCNT is exothermic and spontaneous...
March 22, 2018: Physical Chemistry Chemical Physics: PCCP
Jeannine Steinmeyer, Heidi-Kristin Walter, Mathilde A Bichelberger, Violetta Schneider, Tomáš Kubař, Franziska Rönicke, Bettina Olshausen, Karin Nienhaus, Gerd Ulrich Nienhaus, Ute Schepers, Marcus Elstner, Hans-Achim Wagenknecht
Two fluorescent dyes covalently attached in diagonal interstrand orientation to siRNA undergo energy transfer and thereby enable a dual color fluorescence readout (red/green) for hybridization. Three different structural variations were carried out and compared by their optical properties, including (i) the base surrogate approach with an acyclic linker as a substitute of the 2-deoxyriboside between the phosphodiester bridges, (ii) the 2'-modification of conventional ribofuranosides and (iii) the arabino-configured 2'-modification...
March 22, 2018: Organic & Biomolecular Chemistry
Songcheng Wang, Yi Zhang, J Carson Meredith, Sven H Behrens, Manoj Kumar Tripathi, Kirti Chandra Sahu
Air bubbles rising through an aqueous medium have been studied extensively and are routinely used for the separation of particulates via froth flotation, a key step in many industrial processes. Oil-coated bubbles can be more effective for separating hydrophilic particles with low affinity for the air-water interface, but the rise dynamics of oil-coated bubbles has not yet been explored. In the present work, we report the first systematic study of the shape and rise trajectory of bubbles engulfed in a layer of oil...
March 22, 2018: Soft Matter
C S Dias, J M Tavares, N A M Araújo, M M Telo da Gama
Low-density networks of molecules or colloids are formed at low temperatures when the interparticle interactions are valence limited. Prototypical examples are networks of patchy particles, where the limited valence results from highly directional pairwise interactions. We combine extensive Langevin simulations and Wertheim's theory of association to study these networks. We find a scale-free (relaxation) dynamics within the liquid-gas coexistence region, which differs from that usually observed for isotropic particles...
March 22, 2018: Soft Matter
Lingci Zhao, Irina P Suarez, Diego F Gauto, Rodolfo M Rasia, Jin Wang
The intrinsically disordered protein domain DCL1-A is the first report of a complete double stranded RNA binding domain folding upon binding. DCL1-A recognizes the dsRNA by acquiring a well-folded structure after engagement with its interaction partner. Despite the structural characterization of the interaction complex underlying the recognition of dsRNA has been established, the dynamics of disorder-to-order transitions in the binding process remains elusive. Here we have developed a coarse-grained structure-based model with consideration of electrostatic interactions to explore the mechanism of the coupled folding and binding...
March 22, 2018: Physical Chemistry Chemical Physics: PCCP
T Mondal
The static and dynamic aspects of the T2 ⊗ (e + t2) Jahn-Teller coupling effects in the X[combining tilde]2T2 electronic state of the AlH4 radical are investigated theoretically by probing the first photodetachment spectrum of AlH4-. Associated potential energy surfaces up to two-dimensional space of nuclear coordinates are established from extensive electronic structure calculations and nuclear dynamics calculations are done on them via wave packet propagation including the nonadiabatic coupling of the three electronic sheets...
March 22, 2018: Physical Chemistry Chemical Physics: PCCP
Michalina Błażkiewicz, Ida Wiszomirska, Katarzyna Kaczmarczyk, Andrzej Wit
BACKGROUND: Falls constitute an important health issue. They cause significant morbidity, mortality and have marked psychological effects on the individual, too. The aim of this study has been to determine parameters describing human movement strategies for balance and the reaction if balance is lost as a result of an unstable ground, and to attempt to describe the types of falls. MATERIAL AND METHODS: The study group comprised 20 volunteers. Kinematic parameters of falling and dynamic stability were measured using the Vicon Motion System and the Biodex Balance System SD...
March 15, 2018: Medycyna Pracy
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