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Melinda M Diver, Leanne Pedi, Akiko Koide, Shohei Koide, Stephen B Long
The maturation of RAS GTPases and approximately 200 other cellular CAAX proteins involves three enzymatic steps: addition of a farnesyl or geranylgeranyl prenyl lipid to the cysteine (C) in the C-terminal CAAX motif, proteolytic cleavage of the AAX residues and methylation of the exposed prenylcysteine residue at its terminal carboxylate. This final step is catalysed by isoprenylcysteine carboxyl methyltransferase (ICMT), a eukaryote-specific integral membrane enzyme that resides in the endoplasmic reticulum...
January 17, 2018: Nature
Timothy Lovorn, Sanjoy K Sarker
Metal oxides such as VO_{2} undergo structural transitions to low-symmetry phases characterized by intricate crystalline order, accompanied by rich electronic behavior. We derive a minimal ionic Hamiltonian based on symmetry and local energetics which describes structural transitions involving all four observed phases, in the correct order. An exact analysis shows that complexity results from the symmetry-induced constraints of the parent phase, which forces ionic displacements to form multiple interpenetrating groups using low-dimensional pathways and distant neighbors...
July 28, 2017: Physical Review Letters
Jan Müller, Jayaraman Rajeswari, Ping Huang, Yoshie Murooka, Henrik M Rønnow, Fabrizio Carbone, Achim Rosch
Skyrmions are nanometric spin whirls that can be stabilized in magnets lacking inversion symmetry. The properties of isolated Skyrmions embedded in a ferromagnetic background have been intensively studied. We show that single Skyrmions and clusters of Skyrmions can also form in the helical phase and investigate theoretically their energetics and dynamics. The helical background provides natural one-dimensional channels along which a Skyrmion can move rapidly. In contrast to Skyrmions in ferromagnets, the Skyrmion-Skyrmion interaction has a strong attractive component and thus Skyrmions tend to form clusters with characteristic shapes...
September 29, 2017: Physical Review Letters
Mostafa Youssef, Krystyn J Van Vliet, Bilge Yildiz
We demonstrate a thermodynamic formulation to quantify defect formation energetics in an insulator under a high electric field. As a model system, we analyzed neutral oxygen vacancies (color centers) in alkaline-earth-metal binary oxides using density functional theory, Berry phase calculations, and maximally localized Wannier functions. The work of polarization lowers the field-dependent electric Gibbs energy of formation of this defect. This is attributed mainly to the ease of polarizing the two electrons trapped in the vacant site, and secondarily to the defect induced reduction in bond stiffness and softening of phonon modes...
September 22, 2017: Physical Review Letters
N C Michenfelder, H A Ernst, C Schweigert, M Olzmann, A-N Unterreiner
Early-time dynamics of nitroaromatics and its coressponding bases can give valuable insights into photo-induced reactions relevant to atmospheric and environmental processes. In this work, femtosecond broadband absorption spectroscopy between 350 and 700 nm has been applied to explore the ultrafast dynamics of o-, p- and m-nitrophenol anions (NP-) in basic organic and aqueous solution. Excitation at 400 nm promotes these compounds into the first bright electronic singlet state, which is a charge-transfer state...
January 17, 2018: Physical Chemistry Chemical Physics: PCCP
Tim Bonham, Gillian V Pepper, Daniel Nettle
Background: Although people generally feel more positive and more energetic in the aftermath of exercise than before, longitudinal research on how exercise relates to within-person fluctuations in affect over the course of everyday life is still relatively limited. One constraint on doing such research is the need to provide participants with accelerometers to objectively record their exercise, and pagers to capture affective reports. Aims: We aimed to develop a methodology for studying affect and exercise using only technology that participants already possess, namely GPS running watches and smartphones...
2018: PeerJ
Nichole F Huntley, John F Patience
Xylose, as β-1,4-linked xylan, makes up much of the hemicellulose in cell walls of cereal carbohydrates fed to pigs. As inclusion of fibrous ingredients in swine diets continues to increase, supplementation of carbohydrases, such as xylanase, is of interest. However, much progress is warranted to achieve consistent enzyme efficacy, including an improved understanding of the utilization and energetic contribution of xylanase hydrolysis product (i.e. xylooligosaccharides or monomeric xylose). This review examines reports on xylose absorption and metabolism in the pig and identifies gaps in this knowledge that are essential to understanding the value of carbohydrase hydrolysis products in the nutrition of the pig...
2018: Journal of Animal Science and Biotechnology
Laith A Algharagholy, Tom Pope, Colin J Lambert
We show that carbon-based nanostructured materials are a novel testbed for controlling thermoelectricity and have the potential to underpin the development of new cost-effective environmentally-friendly thermoelectric materials. In single-molecule junctions, it is known that transport resonances associated with the discrete molecular levels play a key role in the thermoelectric performance, but such resonances have not been exploited in carbon nanotubes (CNTs). Here we study junctions formed from tapered CNTs and demonstrate that such structures possess transport resonances near the Fermi level, whose energetic location can be varied by applying strain, resulting in an ability to tune the sign of their Seebeck coefficient...
January 17, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Yu Wen, Dehong Xia
The purpose of this study is to provide scientific guidance for morphological control of nanoparticle synthesis by gas phase method. A universal thermodynamics model is developed to predict morphology of nanoparticles fabricated by inert gas condensation method. By the use of the model, morphologies of aluminum nanocrystals are predicted under various preparation conditions. There are two kinds of energies that determine the formation of nanoparticles morphology jointly, which are Gibbs free energy for nanoparticles and energy variation during the process...
January 17, 2018: Nanotechnology
Martin Picard, Bruce S McEwen, Elissa Epel, Carmen Sandi
Energy is required to sustain life and enable stress adaptation. At the cellular level, energy is largely derived from mitochondria - unique multifunctional organelles with their own genome. Four main elements connect mitochondria to stress: 1) Energy is required at the molecular, (epi)genetic, cellular, organ, and systemic levels to sustain components of stress responses; 2) Glucocorticoids and other steroid hormones are produced and metabolized by mitochondria; 3) Reciprocally, mitochondria functionally respond to neuroendocrine and metabolic stress mediators; and 4) Experimentally manipulating mitochondrial functions alters physiological and behavioral responses to psychological stress...
January 12, 2018: Frontiers in Neuroendocrinology
Attilio Vittorio Vargiu, Venkata Krishnan Ramaswamy, Ivana Malvacio, Giuliano Malloci, Ulrich Kleinekathöfer, Paolo Ruggerone
BACKGROUND: Efflux pumps of the Resistance-Nodulation-cell Division superfamily confer multi-drug resistance to Gram-negative bacteria. The most-studied polyspecific transporter belonging to this class is the inner-membrane trimeric antiporter AcrB of Escherichia coli. In previous studies, a functional rotation mechanism was proposed for its functioning, according to which the three monomers undergo concerted conformational changes facilitating the extrusion of substrates. However, the molecular determinants and the energetics of this mechanism still remain unknown, so its feasibility must be proven mechanistically...
January 12, 2018: Biochimica et Biophysica Acta
David Danovich, Cina Foroutan-Nejad, Philippe Charles Hiberty, Sason Shaik
We analyze the properties of fifteen 3-electron bonds, which include σ-3-electron-bonds, such as dihalide radical anions and di-Noble gas radical cations, π-3-electron-bonds as in hydrazine-radical cation, and doubly-π-(3e)-bonded species such as O2, FeO+, S2, etc. The primary analytical tool is the breathing-orbital valence-bond (BOVB) method, which enables us to quantify the charge-shift resonance energy (RECS) of the 3-electrons, and the bond dissociation energies (De). BOVB is tested reliable against MRCI calculations...
January 16, 2018: Journal of Physical Chemistry. A
Philippe B Wilson, Ian H Williams
DFT calculations for CH3+ within a constrained cage of water molecules permit the controlled manipulation of distances rax and req to "axial" and "equatorial" waters. Equatorial CH…O interactions catalyze methyl transfer (MT) between axial waters. Variation in rax has a greater effect on CH bond lengths and stretching force constants in the symmetric SN2-like transition structures than variation in req. In-plane bending frequencies are insensitive to these variations in cage dimensions, but axial interactions loosen the out-of-plane bending mode (OP) whereas equatorial interactions stiffen it...
January 16, 2018: Journal of Physical Chemistry. A
Anastasia Leventis, Jeroen Royakkers, Alexandros G Rapidis, Niall Goodeal, Merina K Corpinot, Jarvist M Frost, Dejan-Krešimir Bučar, Matthew Oliver Blunt, Franco Cacialli, Hugo Bronstein
We present the synthesis and characterisation of a series of encap-sulated diketopyrrolopyrrole red-emitting conjugated polymers. The novel materials display extremely high fluorescence quantum yields in both solution (>70%) and thin film (>20%). Both the absorption and emission spectra show clearer, more defined features compared to their naked counterparts demonstrating the suppression of inter and intra-molecular aggregation. We find that the encapsulation results in decreased energetic disorder and a dramatic increase in backbone co-linearity as evidenced by STM...
January 16, 2018: Journal of the American Chemical Society
M L E Hernández-Palomares, J A Godoy-Lugo, S Gómez-Jiménez, L A Gámez-Alejo, R M Ortiz, J F Muñoz-Valle, A B Peregrino-Uriarte, G Yepiz-Plascencia, J A Rosas-Rodríguez, J G Soñanez-Organis
Lactate dehydrogenase (LDH) is key for anaerobic glycolysis. LDH is induced by the hypoxia inducible factor -1 (HIF-1). HIF-1 induces genes involved in glucose metabolism and regulates cellular oxygen homeostasis. HIF-1 is formed by a regulatory α-subunit (HIF-1α) and a constitutive β-subunit (HIF-1β). The white spot syndrome virus (WSSV) induces anaerobic glycolysis in shrimp hemocytes, associated with lactate accumulation. Although infection and lactate production are associated, the LDH role in WSSV-infected shrimp has not been examined...
January 11, 2018: Fish & Shellfish Immunology
Sarah Tomas-Hernández, Jordi Blanco, Cristina Rojas, Joel Roca-Martínez, María José Ojeda-Montes, Raúl Beltrán-Debón, Santiago Garcia-Vallve, Gerard Pujadas, Lluís Arola, Miquel Mulero
SCOPE: Resveratrol (RSV) has been described as a potent antioxidant, anti-steatotic, and antitumor compound, and it has also been identified as a potent autophagy inducer. On the other hand, quercetin (QCT) is a dietary flavonoid with known antitumor, anti-inflammatory and antidiabetic effects. Additionally, QCT increases autophagy. To study the hypothetical synergistic effect of both compounds, we tested the combined effect of QCT and RSV on the autophagy process in HepG2 cells METHODS AND RESULTS: Autophagy was studied by western blotting, real-time RT-PCR, and cellular staining...
January 16, 2018: Molecular Nutrition & Food Research
Madhulika Gupta, Prabir Khatua, Charusita Chakravarty, Sanjoy Bandyopadhyay
The microscopic properties of water confined within different segments of Trpzip4 (TZ4), Trpzip5 (TZ5) and Trzpip6 (TZ6) have been compared for all the states characterized along their folding pathways. In particular, structural ordering, energetics, and dynamics of water have been examined as the peptide unfolds along the free energy landscape. It is observed that the structuring of tetrahedral network as well as translational and rotational motions of hydration waters confined within the strands and the turn regions are very different, revealing motional heterogeneity in small 16-residue trpzips...
January 15, 2018: Journal of Physical Chemistry. B
Daniel Fritsch
Spinel ferrites in general show a rich interplay of structural, electronic, and magnetic properties. Here, we particularly focus on zinc ferrite (ZFO), which has been observed experimentally to crystallise in the cubic <i>normal</i> spinel structure. However, its magnetic ground state is still under dispute. In addition, some unusual magnetic properties in ZFO thin films or nanostructures have been explained by a possible partial cation inversion and a different magnetic interaction between the two cation sublattices of the spinel structure compared to the crystalline bulk material...
January 15, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Jack Strand, Moloud Kaviani, Valeri V Afanas'ev, Judit Lisoni, Alexander L Shluger
We demonstrate that electron trapping at intrinsic precursor sites is endemic to non-glass-forming amorphous oxide films. The energy distributions of trapped electron states in ultra-pure prototype amorphous (a)-HfO<sub>2</sub> insulator obtained from exhaustive photo-depopulation experiments demonstrate the electron states in the energy range of 2-3 eV below the oxide conduction band. These energy distributions are compared to the results of density functional calculations of a-HfO<sub>2</sub> models of realistic density...
January 15, 2018: Nanotechnology
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