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https://www.readbyqxmd.com/read/28723063/using-cooperatively-folded-peptides-to-measure-interaction-energies-and-conformational-propensities
#1
Maziar S Ardejani, Evan T Powers, Jeffery W Kelly
The rates and equilibria of the folding of biopolymers are determined by the conformational preferences of the subunits that make up the sequence of the biopolymer and by the interactions that are formed in the folded state in aqueous solution. Because of the centrality of these processes to life, quantifying conformational propensities and interaction strengths is vitally important to understanding biology. In this Account, we describe our use of peptide model systems that fold cooperatively yet are small enough to be chemically synthesized to measure such quantities...
July 19, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28710647/impacts-of-sublethal-mercury-exposure-on-birds-a-detailed-review
#2
Margaret C Whitney, Daniel A Cristol
Mercury is a ubiquitous environmental contaminant known to accumulate in, and negatively affect, fish-eating and oceanic bird species, and recently demonstrated to impact some terrestrial songbirds to a comparable extent. It can bioaccumulate to concentrations of >1 μg/g in tissues of prey organisms such as fish and insects. At high enough concentrations, exposure to mercury is lethal to birds. However, environmental exposures are usually far below the lethal concentrations established by dosing studies...
July 15, 2017: Reviews of Environmental Contamination and Toxicology
https://www.readbyqxmd.com/read/28707684/conformer-specific-nonadiabatic-reaction-dynamics-in-the-photodissociation-of-partially-deuterated-thioanisoles-c6h5s-ch2d-and-c6h5s-chd2
#3
So-Yeon Kim, Jeongmook Lee, Sang Kyu Kim
In this work, we have investigated nonadiabatic dynamics in the vicinity of conical intersections for predissociation reactions of partially deuterated thioanisole molecules: C6H5S-CH2D and C6H5S-CHD2. Each isotopomer has two distinct rotational conformers according to the geometrical position of D or H of the methyl moiety with respect to the molecular plane for C6H5S-CH2D or C6H5S-CHD2, respectively, as spectroscopically characterized in our earlier report [J. Lee, S.-Y. Kim and S. K. Kim, J. Phys. Chem. A, 2014, 118, 1850]...
July 14, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28697411/electron-velocity-map-imaging-and-theoretical-study-on-cuxh-x-o-and-s-anions
#4
Zhengbo Qin, Hui Wang, Yangdi Ren, Xianfeng Zheng, Zhifeng Cui, Zichao Tang
Vibrationally resolved photoelectron spectra of CuOH(-) and CuSH(-) have been determined via velocity map imaging method to investigate the transitions of X(1)A'←X(2)A' at 532nm. Adiabatic detachment energies of CuOH(-) and CuSH(-) are assigned to 0.995(12) and 1.098(12) eV, respectively. Combined theoretical calculations with Franck-Condon simulations, it allows extracting the vibrational frequencies in neutral, which yields 629(32) cm(-1) with CuO stretching mode and 387(24) cm(-1) with CuS stretching mode for CuXH (X=O and S)...
July 4, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28671226/kinetically-modulated-specificity-against-single-base-mutants-in-nucleic-acid-recycling-circuitry-using-the-destabilization-motif
#5
Tsz Wing Fan, I-Ming Hsing
Signal amplification in nucleic acid sensing improves detection sensitivity, but difficulties remain in sustaining specificity over time, particularly under excess amounts of single-base mutants. Here, we report simple, self-refining target recycling circuitry, which cumulates differentiation between on and off targets by 2-step cyclic interaction with the sensing probe. In the reaction, the analyte recycles only if the protective strand of the sensing probe is removed. The dissociation kinetics of such interaction was modulated by reacting it with different lengths of assistant strands...
July 3, 2017: Analyst
https://www.readbyqxmd.com/read/28662468/novel-carbohydrate-substituted-metallo-porphyrazine-comparison-for-cancer-tissue-type-specificity-during-pdt
#6
Tamarisk K Horne, Marianne J Cronjé
A longstanding obstacle to cancer eradication centers on the heterogeneous nature of the tissue that manifests it. Variations between cancer cell resistance profiles often result in a survival percentage following classic therapeutics. As an alternative, photodynamic therapys' (PDT) unique non-specific cell damage mechanism and high degree of application control enables it to potentially deliver an efficient treatment regime to a broad range of heterogeneous tissue types thereby overcoming individual resistance profiles...
June 12, 2017: Journal of Photochemistry and Photobiology. B, Biology
https://www.readbyqxmd.com/read/28656516/targeting-mitochondrial-calcium-handling-and-reactive-oxygen-species-in-heart-failure
#7
REVIEW
Alexander Dietl, Christoph Maack
PURPOSE OF REVIEW: In highly prevalent cardiac diseases, new therapeutic approaches are needed. Since the first description of oxidative stress in heart failure, reactive oxygen species (ROS) have been considered as attractive drug targets. Though clinical trials evaluating antioxidant vitamins as ROS-scavenging agents yielded neutral results in patients at cardiovascular risk, the knowledge of ROS as pathophysiological factors has considerably advanced in the past few years and led to novel treatment approaches...
June 27, 2017: Current Heart Failure Reports
https://www.readbyqxmd.com/read/28640522/defective-tungsten-oxide-hydrate-nanosheets-for-boosting-aerobic-coupling-of-amines-synergistic-catalysis-by-oxygen-vacancies-and-br%C3%A3-nsted-acid-sites
#8
Ning Zhang, Xiyu Li, Yifei Liu, Ran Long, Mengqiao Li, Shuangming Chen, Zeming Qi, Chengming Wang, Li Song, Jun Jiang, Yujie Xiong
Adsorption and activation of molecules on a surface holds the key to heterogeneous catalysis toward aerobic oxidative reactions. To achieve high catalytic activities, a catalyst surface should be rationally tailored to interact with both organic substrates and oxygen molecules. Here, a facile bottom-up approach to defective tungsten oxide hydrate (WO3 ·H2 O) nanosheets that contain both surface defects and lattice water is reported. The defective WO3 ·H2 O nanosheets exhibit excellent catalytic activity for aerobic coupling of amines to imines...
June 22, 2017: Small
https://www.readbyqxmd.com/read/28628631/computational-explanation-for-bioactivation-mechanism-of-targeted-anticancer-agents-mediated-by-cytochrome-p450s-a-case-of-erlotinib
#9
Chun-Zhi Ai, Yong Liu, Wei Li, De-Meng Chen, Xin-Xing Zhu, Ya-Wei Yan, Du-Chu Chen, Yi-Zhou Jiang
EGFR inhibitors, even with therapeutics superiorities in anticancer, can cause idiosyncratic pulmonary and hepatic toxicities that are associated with the reactive electrophile bioactivated by Cytochrome P450s (P450s). Until now, neither has the electrophilic intermediate been caught experimentally, nor has the subtle mechanism been declared. Herein, the underlying mechanism of bioactivation mediated by P450s was explored by DFT calculations for a case of EGFR inhibitor, Erlotinib. Based on the calculation and analysis, we suggest that with other metabolites, reactive electrophiles of Erlotinib: epoxide and quinine-imine, can be generated by several steps along the oxidative reaction pathway...
2017: PloS One
https://www.readbyqxmd.com/read/28625787/structural-snapshots-and-loop-dynamics-along-the-catalytic-cycle-of-glycosyltransferase-gpgs
#10
David Albesa-Jové, Javier Romero-García, Enea Sancho-Vaello, F-Xabier Contreras, Ane Rodrigo-Unzueta, Natalia Comino, Ana Carreras-González, Pedro Arrasate, Saioa Urresti, Xevi Biarnés, Antoni Planas, Marcelo E Guerin
Glycosyltransferases (GTs) play a central role in nature. They catalyze the transfer of a sugar moiety to a broad range of acceptor substrates. GTs are highly selective enzymes, allowing the recognition of subtle structural differences in the sequences and stereochemistry of their sugar and acceptor substrates. We report here a series of structural snapshots of the reaction center of the retaining glucosyl-3-phosphoglycerate synthase (GpgS). During this sequence of events, we visualize how the enzyme guides the substrates into the reaction center where the glycosyl transfer reaction takes place, and unveil the mechanism of product release, involving multiple conformational changes not only in the substrates/products but also in the enzyme...
July 5, 2017: Structure
https://www.readbyqxmd.com/read/28621954/van-der-waals-contribution-to-the-relative-stability-of-aqueous-zn-2-coordination-states
#11
Manoj Ducher, Fabio Pietrucci, Etienne Balan, Guillaume Ferlat, Lorenzo Paulatto, Marc Blanchard
Many properties of aqueous cations depend on their coordination state. However, the lack of long-range order and the dynamic character of aqueous solutions make it difficult to obtain information beyond average coordination parameters. A thorough understanding of the molecular-scale environment of aqueous cations usually requires a combination of experimental and theoretical approaches. In the case of Zn(2+), significant discrepancies occur among theoretical investigations based on first-principles molecular dynamics (FPMD) or free-energy calculations, although experimental data consistently point to a dominant hexaaquo-zinc complex (Zn[H2O]6)(2+) in pure water...
June 28, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28618231/a-high-resolution-study-of-dynamic-changes-of-ce2o3-and-ceo2-nanoparticles-in-complex-environmental-media
#12
Ruth C Merrifield, Kenton P Arkill, Richard E Palmer, Jamie R Lead
Ceria nanoparticles (NPs) rapidly and easily cycle between Ce(III) and Ce(IV) oxidation states, making them prime candidates for commercial and other applications. Increased commercial use has resulted in increased discharge to the environment and increased associated risk. Once in complex media such as environmental waters or toxicology exposure media, the same redox transformations can occur, causing altered behavior and effects compared to the pristine NPs. This study used high resolution scanning transmission electron microscopy and electron energy loss spectroscopy to investigate changes in structure and oxidation state of small, polymer-coated ceria suspensions in complex media...
June 29, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28613239/time-frequency-analysis-of-non-stationary-biological-signals-with-sparse-linear-regression-based-fourier-linear-combiner
#13
Yubo Wang, Kalyana C Veluvolu
It is often difficult to analyze biological signals because of their nonlinear and non-stationary characteristics. This necessitates the usage of time-frequency decomposition methods for analyzing the subtle changes in these signals that are often connected to an underlying phenomena. This paper presents a new approach to analyze the time-varying characteristics of such signals by employing a simple truncated Fourier series model, namely the band-limited multiple Fourier linear combiner (BMFLC). In contrast to the earlier designs, we first identified the sparsity imposed on the signal model in order to reformulate the model to a sparse linear regression model...
June 14, 2017: Sensors
https://www.readbyqxmd.com/read/28598631/thermally-activated-tunneling-transition-in-a-photoswitchable-single-molecule-electrical-junction
#14
Na Xin, Chuancheng Jia, Jinying Wang, Shuopei Wang, Mingliang Li, Yao Gong, Guangyu Zhang, Daoben Zhu, Xuefeng Guo
Exploring the charge transport process in molecular junctions is essential to the development of molecular electronics. Here, we investigate the temperature-dependent charge transport mechanism of carbon electrode-diarylethene single-molecule junctions, which possess photocontrollable molecular orbital energy levels due to reversible photoisomerization of individual diarylethenes between open and closed conformations. Both the experimental results and theoretical calculations consistently demonstrate that the vibronic coupling (thermally activated at the proper temperature) drives the transition of charge transport in the junctions from coherent tunneling to incoherent transport...
June 12, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28597191/theoretical-analysis-of-the-binding-of-iron-iii-protoporphyrin-ix-to-4-methoxyacetophenone-thiosemicarbazone-via-dft-d3-mep-qtaim-nci-elf-and-lol-studies
#15
Nyiang Kennet Nkungli, Julius Numbonui Ghogomu
Thiosemicarbazones display diverse pharmacological properties, including antimalarial activities. Their pharmacological activities have been studied in depth, but little of this research has focused on their antimalarial mode of action. To elucidate this antimalarial mechanism, we investigated the nature of the interactions between iron(III) protoporphyrin IX (Fe(III)PPIX) and the thione-thiol tautomers of 4-methoxyacetophenone thiosemicarbazone (MAPTSC). Dispersion-corrected density functional theory (DFT-D3), the quantum theory of atoms in molecules (QTAIM), the noncovalent interaction (NCI) index, the electron localization function (ELF), the localized orbital locator (LOL), and thermodynamic calculations were employed in this work...
July 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28587814/motion-energy-analysis-reveals-altered-body-movement-in-youth-at-risk-for-psychosis
#16
Derek J Dean, Alayna T Samson, Raeana Newberry, Vijay A Mittal
BACKGROUND: Growing evidence suggests that movement abnormalities occur prior to the onset of psychosis. Innovations in technology and software provide the opportunity for a fine-tuned and sensitive measurement of observable behavior that may be particularly useful to detecting the subtle movement aberrations present during the prodromal period. METHODS: In the present study, 54 youth at ultrahigh risk (UHR) for psychosis and 62 healthy controls participated in structured clinical interviews to assess for an UHR syndrome...
June 3, 2017: Schizophrenia Research
https://www.readbyqxmd.com/read/28580048/probing-transient-valence-orbital-changes-with-picosecond-valence-to-core-x-ray-emission-spectroscopy
#17
Anne Marie March, Tadesse A Assefa, Christina Boemer, Christian Bressler, Alexander Britz, Michael Diez, Gilles Doumy, Andreas Galler, Manuel Harder, Dmitry Khakhulin, Zoltán Németh, Mátyás Pápai, Sebastian Schulz, Stephen H Southworth, Hasan Yavaş, Linda Young, Wojciech Gawelda, György Vankó
We probe the dynamics of valence electrons in photoexcited [Fe(terpy)2](2+) in solution to gain deeper insight into the Fe-ligand bond changes. We use hard X-ray emission spectroscopy (XES), which combines element specificity and high penetration with sensitivity to orbital structure, making it a powerful technique for molecular studies in a wide variety of environments. A picosecond-time-resolved measurement of the complete 1s X-ray emission spectrum captures the transient photoinduced changes and includes the weak valence-to-core (vtc) emission lines that correspond to transitions from occupied valence orbitals to the nascent core-hole...
February 9, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
https://www.readbyqxmd.com/read/28578581/kinetically-controlled-coassembly-of-multichromophoric-peptide-hydrogelators-and-the-impacts-on-energy-transport
#18
Herdeline Ann M Ardoña, Emily R Draper, Francesca Citossi, Matthew Wallace, Louise C Serpell, Dave J Adams, John D Tovar
We report a peptide-based multichromophoric hydrogelator system, wherein π-electron units with different inherent spectral energies are spatially controlled within peptidic 1-D nanostructures to create localized energy gradients in aqueous environments. This is accomplished by mixing different π-conjugated peptides prior to initiating self-assembly through solution acidification. We can vary the kinetics of the assembly and the degree of self-sorting through the choice of the assembly trigger, which changes the kinetics of acidification...
June 16, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28569331/isolated-alkali-cation-complexes-of-the-antibiotic-ionophore-nonactin-correlation-with-crystalline-structures
#19
Juan Ramón Avilés-Moreno, Francisco Gámez, Giel Berden, Jos Oomens, Bruno Martínez-Haya
The antibiotic activity of nonactin is sustained by its ability to transport K(+) across lipophilic phases, e.g., the cell membranes. Such a feature can be traced back to a specific ionophoric behavior and to a balanced hydrophobicity modulated by the formation of a cation complex. In this study, the dominant conformations and coordination arrangements in the alkali cation complexes (Na(+), K(+), Cs(+)) of nonactin are characterized by means of action vibrational spectroscopy and quantum chemical computations...
June 14, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28561274/statistical-shape-modelling-of-hip-and-lumbar-spine-morphology-and-their-relationship-in-the-mrc-national-survey-of-health-and-development
#20
Anastasia V Pavlova, Fiona R Saunders, Stella G Muthuri, Jennifer S Gregory, Rebecca J Barr, Kathryn R Martin, Rebecca J Hardy, Rachel Cooper, Judith E Adams, Diana Kuh, Richard M Aspden
The anatomical shape of bones and joints is important for their proper function but quantifying this, and detecting pathological variations, is difficult to do. Numerical descriptions would also enable correlations between joint shapes to be explored. Statistical shape modelling (SSM) is a method of image analysis employing pattern recognition statistics to describe and quantify such shapes from images; it uses principal components analysis to generate modes of variation describing each image in terms of a set of numerical scores after removing global size variation...
May 31, 2017: Journal of Anatomy
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