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Kinetic chain

Kunpeng Cui, Zhe Ma, Nan Tian, Fengmei Su, Dong Liu, Liangbin Li
Flow-induced crystallization (FIC) is a typical nonequilibrium phase transition and a core industry subject for the largest group of commercially useful polymeric materials: semicrystalline polymers. A fundamental understanding of FIC can benefit the research of nonequilibrium ordering in matter systems and help to tailor the ultimate properties of polymeric materials. Concerning the crystallization process, flow can accelerate the kinetics by orders of magnitude and induce the formation of oriented crystallites like shish-kebab, which are associated with the major influences of flow on nucleation, that is, raised nucleation density and oriented nuclei...
January 19, 2018: Chemical Reviews
Hyunjoong Chung, Dmytro Dudenko, Fengjiao Zhang, Gabriele D'Avino, Christian Ruzié, Audrey Richard, Guillaume Schweicher, Jérôme Cornil, David Beljonne, Yves Geerts, Ying Diao
Martensitic transition is a solid-state phase transition involving cooperative movement of atoms, mostly studied in metallurgy. The main characteristics are low transition barrier, ultrafast kinetics, and structural reversibility. They are rarely observed in molecular crystals, and hence the origin and mechanism are largely unexplored. Here we report the discovery of martensitic transition in single crystals of two different organic semiconductors. In situ microscopy, single-crystal X-ray diffraction, Raman and nuclear magnetic resonance spectroscopy, and molecular simulations combined indicate that the rotating bulky side chains trigger cooperative transition...
January 18, 2018: Nature Communications
Kyungtae Kim, Akash Arora, Ronald M Lewis, Meijiao Liu, Weihua Li, An-Chang Shi, Kevin D Dorfman, Frank S Bates
Cooling disordered compositionally asymmetric diblock copolymers leads to the formation of nearly spherical particles, each containing hundreds of molecules, which crystallize upon cooling below the order-disorder transition temperature (TODT). Self-consistent field theory (SCFT) reveals that dispersity in the block degrees of polymerization stabilizes various Frank-Kasper phases, including the C14 and C15 Laves phases, which have been accessed experimentally in low-molar-mass poly(isoprene)-b-poly(lactide) (PI-PLA) diblock copolymers using thermal processing strategies...
January 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
Chen Jia
Here we develop an effective approach to simplify two-time-scale Markov chains with infinite state spaces by removal of states with fast leaving rates, which improves the simplification method of finite Markov chains. We introduce the concept of fast transition paths and show that the effective transitions of the reduced chain can be represented as the superposition of the direct transitions and the indirect transitions via all the fast transition paths. Furthermore, we apply our simplification approach to the standard Markov model of single-cell stochastic gene expression and provide a mathematical theory of random gene expression bursts...
September 2017: Physical Review. E
Yasmin Shamsudin Khan, Hugo Gutiérrez de Terán, Johan Åqvist
Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX) 1 and 2 with varying degrees of selectivity. A group of COX-2 selective inhibitors - coxibs - bind in a time-dependent manner through a three-step mechanism, utilizing a side-pocket in the binding site. Coxibs have been extensively probed to identify the structural features regulating the slow tight-binding mechanism responsible for COX-2 selectivity. In this study, we further probe a structurally and kinetically diverse data set of COX inhibitors in COX-2 by molecular dynamics and free energy simulations...
January 18, 2018: Biochemistry
Didier Clénet
Due to their thermosensitivity, most vaccines must be kept refrigerated from production to use. To successfully carry out global immunization programs, ensuring the stability of vaccines is crucial. In this context, two important issues are critical, namely: (i) predicting vaccine stability and (ii) preventing product damage due to excessive temperature excursions outside of the recommended storage conditions (cold chain break). We applied a combination of advanced kinetics and statistical analyses on vaccine forced degradation data to accurately describe the loss of antigenicity for a multivalent freeze-dried inactivated virus vaccine containing three variants...
January 13, 2018: European Journal of Pharmaceutics and Biopharmaceutics
Rui He, Archie C Reyes, Tina L Amyes, John Richard
The side chain of Q295 of glycerol-3-phosphate dehydrogenase from human liver (hlGPDH) lies in a flexible loop. This loop folds over the phosphodianion of substrate dihydroxyacetone phosphate (DHAP), where Q295 interacts with the side chain cation from R269, which is ion-paired to the substrate phosphodianion. Kinetic parameters kcat/Km (M-1 s-1) and kcat/KGAKHPi (M-2 s-1) were determined, respectively, for catalysis of the reduction of DHAP and for dianion activation of catalysis of reduction of glycolaldeyde (GA) catalyzed by wildtype, Q295G, Q295S, Q295A, and Q295N mutants of hlGPDH...
January 16, 2018: Biochemistry
Yo-Han Kwon, Jung Jin Park, Lisa M Housel, Krysten Minnici, Guoyan Zhang, Sujin R Lee, Seung Woo Lee, Zhongming Chen, Suguru Noda, Esther S Takeuchi, Kenneth J Takeuchi, Amy C Marschilok, Elsa Reichmanis
A carbon nanotube (CNT) web electrode comprising magnetite spheres and few-walled carbon nanotubes (FWNTs) linked by the carboxylated conjugated polymer, poly[3-(potassium-4-butanoate) thiophene] (PPBT), was designed to demonstrate benefits derived from the rational consideration of electron/ion transport coupled with the surface chemistry of the electrode materials components. To maximize transport properties, the approach introduces monodispersed spherical Fe3O4 (sFe3O4) for uniform Li+ diffusion and a FWNT web electrode frame that affords characteristics of long-ranged electronic pathways and porous networks...
January 16, 2018: ACS Nano
Steffen Eggers, Volker Abetz
Herein, a reversible addition-fragmentation chain transfer (RAFT) polymerization is introduced for reactive monomers like N-acryloylpyrrolidine or N,N-dimethylacrylamide working without a conventional radical initiator. As a very straightforward proof of principle, the method takes advantage of the usually inconvenient radical-generating hydroperoxide contaminations in cyclic ethers like tetrahydrofuran or 1,4-dioxane, which are very common solvents in polymer sciences. The polymerizations are surprisingly well controlled and the polymers can be extended with a second block, indicating their high livingness...
January 15, 2018: Macromolecular Rapid Communications
Prathitha Kar, Andrey G Cherstvy, Ralf Metzler
Proteins are capable of locating specific targets on DNA by employing a facilitated diffusion process with intermittent 1D and 3D search steps. Gene colocalisation and coregulation-i.e. the spatial proximity of two communicating genes-is one factor capable of accelerating the target search process along the DNA. We perform Monte Carlo computer simulations and demonstrate the benefits of gene colocalisation for minimising the search time in a model DNA-protein system. We use a simple diffusion model to mimic the search for targets by proteins, produced initially in bursts of multiple proteins and performing the first-passage search on the DNA chain...
January 15, 2018: Physical Chemistry Chemical Physics: PCCP
M Nazaret González-Alcaraz, Susana Loureiro, Cornelis A M van Gestel
This study evaluated how different combinations of air temperature (20 °C and 25 °C) and soil moisture content (50% and 30% of the soil water holding capacity, WHC), reflecting realistic climate change scenarios, affect the bioaccumulation kinetics of Zn and Cd in the earthworm Eisenia andrei. Earthworms were exposed for 21 d to two metal-contaminated soils (uptake phase), followed by 21 d incubation in non-contaminated soil (elimination phase). Body Zn and Cd concentrations were checked in time and metal uptake (k1) and elimination (k2) rate constants determined; metal bioaccumulation factor (BAF) was calculated as k1/k2...
January 8, 2018: Chemosphere
H H Katkar, M Muthukumar
One of the major theoretical methods in understanding polymer translocation through a nanopore is the Fokker-Planck formalism based on the assumption of quasi-equilibrium of polymer conformations. The criterion for applicability of the quasi-equilibrium approximation for polymer translocation is that the average translocation time per Kuhn segment, ⟨τ⟩/NK, is longer than the relaxation time τ0 of the polymer. Toward an understanding of conditions that would satisfy this criterion, we have performed coarse-grained three dimensional Langevin dynamics and multi-particle collision dynamics simulations...
January 14, 2018: Journal of Chemical Physics
Ryan A Mlynarek, Struan H Coleman
PURPOSE OF REVIEW: To discuss the clinical significance of the most common hip and groin injuries in baseball players, as well as an algorithmic approach to diagnosis and treatment of these injuries. RECENT FINDINGS: (a) Limitations in throwing velocity, pitch control, and bat swing speed may be secondary to decreased mobility and strength within the proximal kinetic chain, which must harness power from the lower extremities and core. (b) Approximately 5.5% of all baseball injuries per year involve the hip/groin and may lead to a significant amount of time spent on the disabled list...
January 12, 2018: Current Reviews in Musculoskeletal Medicine
Lei Tian, Stéphane Bayen
This study investigated the thermal degradation of a veterinary drug, chloramphenicol, in model solutions (water), as well as in spiked and incurred mussel tissues to understand its fate in the food supply chain. Thermal degradation kinetics followed a first-order model in water (e.g. degradation rate: 0.0018-0.0025 min-1 at 100 °C). After 1 h at 100 °C, the percentage degradation in spiked tissues (28.1 ± 7.1%) was significantly different (p < .05) from the values in water (14.2 ± 1...
May 15, 2018: Food Chemistry
Diego Pinto de Oliveira, Thales do Valle Moreira, Nathália Vieira Batista, José Dias de Souza Filho, Flávio Almeida Amaral, Mauro Martins Teixeira, Rodrigo Maia de Pádua, Fernão Castro Braga
trans-Aconitic acid (TAA) is an abundant constituent in the leaves of Echinodorus grandiflorus, a medicinal plant used to treat rheumatoid arthritis in Brazil. Esterification was explored as a strategy to increase lipophilicity and biopharmaceutical properties of TAA, a highly polar tricarboxylic acid. We herein report the synthesis of TAA esters via Fischer esterification with ethanol, n-butanol and n-octanol. The reaction kinetics was investigated to produce mono-, di- and tri- derivatives. Mono- and diesters of TAA were obtained as a mixture of positional isomers, whereas the triesters were recovered as pure compounds...
January 9, 2018: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Sin-Yi Liou, Wan-Ru Chen
Albendazole (ABZ) is a benzimidazole-based veterinary anthelmintic used extensively in the treatment of intestinal parasites. Due to its high hydrophobicity, ABZ tends to accumulate in soils and sediments in the environment. This study aims to investigate ABZ's possible degradation by manganese oxides. Minor effects from ionic strength and metal cations on ABZ degradation were observed. By contrast, decrease of pH greatly enhanced the reaction rate. Surface complexation between ABZ and MnO2 was indicated to be the dominant control in the reaction kinetics...
December 29, 2017: Journal of Hazardous Materials
Chithra C Sreenivasan, Sunayana S Jandhyala, Sisi Luo, Ben M Hause, Milton Thomas, David E B Knudsen, Pamela Leslie-Steen, Travis Clement, Stephanie E Reedy, Thomas M Chambers, Jane Christopher-Hennings, Eric Nelson, Dan Wang, Radhey S Kaushik, Feng Li
Equine influenza, caused by the H3N8 subtype, is a highly contagious respiratory disease affecting equid populations worldwide and has led to serious epidemics and transboundary pandemics. This study describes the phylogenetic characterization and replication kinetics of recently-isolated H3N8 virus from a nasal swab obtained from a sporadic case of natural infection in an unvaccinated horse from Montana, USA. The nasal swab tested positive for equine influenza by Real-Time Quantitative Reverse Transcription Polymerase Chain Reaction (RT-PCR)...
January 11, 2018: Viruses
Huan-Xiang Zhou, Xiaodong Pang
Charged and polar groups, through forming ion pairs, hydrogen bonds, and other less specific electrostatic interactions, impart important properties to proteins. Modulation of the charges on the amino acids, e.g., by pH and by phosphorylation and dephosphorylation, have significant effects such as protein denaturation and switch-like response of signal transduction networks. This review aims to present a unifying theme among the various effects of protein charges and polar groups. Simple models will be used to illustrate basic ideas about electrostatic interactions in proteins, and these ideas in turn will be used to elucidate the roles of electrostatic interactions in protein structure, folding, binding, condensation, and related biological functions...
January 10, 2018: Chemical Reviews
Ryan D Cassaday, Philip A Stevenson, Brent L Wood, Pamela S Becker, Paul C Hendrie, Brenda M Sandmaier, Jerald L Radich, Andrei R Shustov
HyperCVAD is a commonly-used regimen for adults with newly-diagnosed acute lymphoblastic leukemia (ALL). However, relatively little is known about the application of minimal residual disease (MRD) detection with this treatment. To address this, we studied 142 adults with ALL treated with hyperCVAD over a 10-year period who had MRD assessed by either multi-parameter flow cytometry or (for patients with Philadelphia chromosome positive ALL) reverse transcriptase polymerase chain reaction for the BCR-ABL1 translocation...
January 10, 2018: American Journal of Hematology
Alexandra T P Carvalho, Daniel F A R Dourado, Timofey Skvortsov, Miguel de Abreu, Lyndsey J Ferguson, Derek J Quinn, Thomas S Moody, Meilan Huang
Phenylacetone monooxygenase is the most stable and thermo-tolerant member of the Baeyer-Villiger monooxygenases family, and therefore it is an ideal candidate for the synthesis of industrially relevant ester or lactone compounds. However, its limited substrate scope has largely limited its industrial applications. Linear substrates are interesting from an industrial point of view, it is thus necessary to identify the essential spatial requirement for achieving high conversions for non-native linear substrates...
January 10, 2018: Physical Chemistry Chemical Physics: PCCP
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