- Comparison of composition-gradient sedimentation equilibrium and composition-gradient static light scattering as techniques for quantitative characterization of biomolecular interactions: A case study. [Journal Article]
- ABAnal Biochem 2019 Jul 15
- The equilibrium hetero-association of NADH oxidase and peroxiredoxin was characterized by means of independently conducted measurements of composition-gradient sedimentation equilibrium and compositi…
The equilibrium hetero-association of NADH oxidase and peroxiredoxin was characterized by means of independently conducted measurements of composition-gradient sedimentation equilibrium and composition-gradient static light scattering. Results obtained from both experiments were quantitatively accounted for by a model according to which a dimer of NADH oxidase forms a 1:1 equilibrium complex with a decamer of peroxiredoxin under the conditions of these experiments. The best-fit equilibrium constants for heteroassociation of the two proteins obtained from the two measurements were found to be identical to well within the uncertainty of estimate of each of the two methods. The relative virtues of each of the methods are discussed.
- ABCE1 Controls Ribosome Recycling by an Asymmetric Dynamic Conformational Equilibrium. [Journal Article]
- CRCell Rep 2019 Jul 16; 28(3):723-734.e6
- The twin-ATPase ABCE1 has a vital function in mRNA translation by recycling terminated or stalled ribosomes. As for other functionally distinct ATP-binding cassette (ABC) proteins, the mechanochemica…
The twin-ATPase ABCE1 has a vital function in mRNA translation by recycling terminated or stalled ribosomes. As for other functionally distinct ATP-binding cassette (ABC) proteins, the mechanochemical coupling of ATP hydrolysis to conformational changes remains elusive. Here, we use an integrated biophysical approach allowing direct observation of conformational dynamics and ribosome association of ABCE1 at the single-molecule level. Our results from FRET experiments show that the current static two-state model of ABC proteins has to be expanded because the two ATP sites of ABCE1 are in dynamic equilibrium across three distinct conformational states: open, intermediate, and closed. The interaction of ABCE1 with ribosomes influences the conformational dynamics of both ATP sites asymmetrically and creates a complex network of conformational states. Our findings suggest a paradigm shift to redefine the understanding of the mechanochemical coupling in ABC proteins: from structure-based deterministic models to dynamic-based systems.
- Association between bone mass and functional capacity among elderly people aged 80 years and over. [Journal Article]
- RBRev Bras Ortop 2013 Nov-Dec; 48(6):512-518
- CONCLUSIONS: Thus, the bone of the femur for the oldest old male is associated with functional capacity. The constant assessment of the bone mineral mass and practive of physical activity throughout life would be measures to prevent falls in the elderly.
- The Glucagon-Like Peptide 2 Analog Teduglutide Reversibly Associates to Form Pentamers. [Journal Article]
- JPJ Pharm Sci 2019 Jul 12
- Glucagon-like peptide 1 and 2 (GLP-1 and GLP-2) and their analog peptide therapeutics are known to reversibly associate to form oligomers. Here we report the association properties of the GLP-2 analo…
Glucagon-like peptide 1 and 2 (GLP-1 and GLP-2) and their analog peptide therapeutics are known to reversibly associate to form oligomers. Here we report the association properties of the GLP-2 analog teduglutide at concentrations up to ∼15 mg/mL. Both sedimentation equilibrium (SE-AUC) and sedimentation velocity (SV-AUC) show that teduglutide dissociates completely to monomers below 0.1 mg/mL. SE-AUC shows that the apparent weight-average molar mass increases substantially between 0.1 and 1 mg/mL, reaching a maximum of ∼14.5 kDa (∼3.9-mer) near 2 mg/mL, and then falling at higher concentrations due to strong solution non-ideality effects (highly positive second virial coefficient). Circular dichroism spectra over the range from 0.1 to 2 mg/mL show that self-association is accompanied by significant increases in alpha-helix content, and that the associated state has a distinct tertiary structure. The SV-AUC data up to 2.2 mg/mL are fitted fairly well by an ideal rapidly-reversible monomer-pentamer association. The SE-AUC modeling included thermodynamic non-ideality effects. SE-AUC data up to ∼15 mg/ml imply a monomer-pentamer association at lower concentrations, but the pentamers also appear to weakly associate to form decamers. These results illustrate the importance of directly modeling the solution non-ideality effects, which if neglected would lead to an incorrect preferred stoichiometry.
- Synergistic inhibition of catalase activity by food colorants sunset yellow and curcumin: An experimental and MLSD simulation approach. [Journal Article]
- CBChem Biol Interact 2019 Jul 10; :108746
- Utilizing food additives at their optimized concentration is believed to be relatively safe, but their combinatorial effects remain largely unexplored. The influence of mixed food additives on the ma…
Utilizing food additives at their optimized concentration is believed to be relatively safe, but their combinatorial effects remain largely unexplored. The influence of mixed food additives on the macromolecules may be altered by synergistic or antagonistic effects. It is previously shown that curcumin enhances the catalase activity by affecting its structural pocket in the active site. The aim of this study was to investigate the combination effects of food colorants sunset yellow FCF (SNY) and curcumin on the activation and/or inactivation of catalase activity using multispectral (fluorescence, FTIR, and UV-vis) analysis and simultaneous docking simulations. Kinetic studies demonstrated that SNY could significantly decrease catalase activity through a non-competitive inhibition mechanism. Fluorescence data indicated that SNY reduces intrinsic emission of catalase via a static quenching mechanism. Thermodynamic and molecular docking investigations suggested that catalase has one binding site for SNY, and hydrogen binding plays a main role in the binding reaction of catalase -SNY complex. Molecular dynamic simulation data indicated that the curcumin binding to the cavity, in the middle of the catalase helical domain, facilitates SNY binding to the enzyme pocket. For this purpose, the equilibrium dialysis system was used to study the stability and reversibility of SNY-catalase in the absence or presence of curcumin. The obtained data indicated that the binding of SNY-catalase is reversible and the stability of the complex is time-dependent. However, curcumin could make the complex more stable enhancing the SNY inhibition of catalase activity.
- Measuring preschool children's knowledge of the principle of static equilibrium in the context of building blocks: Validation of a test instrument. [Journal Article]
- BJBr J Educ Psychol 2019 Jul 10
- CONCLUSIONS: The Centre-of-Mass Test measures knowledge of the principle of static equilibrium as a unidimensional construct and mirrors preschoolers' estimations found in previous studies. The acquisition of a more sophisticated static equilibrium knowledge is related to spatial knowledge and language capacity.
- α-Rank: Multi-Agent Evaluation by Evolution. [Journal Article]
- SRSci Rep 2019 Jul 09; 9(1):9937
- We introduce α-Rank, a principled evolutionary dynamics methodology, for the evaluation and ranking of agents in large-scale multi-agent interactions, grounded in a novel dynamical game-theoretic sol…
We introduce α-Rank, a principled evolutionary dynamics methodology, for the evaluation and ranking of agents in large-scale multi-agent interactions, grounded in a novel dynamical game-theoretic solution concept called Markov-Conley chains (MCCs). The approach leverages continuous-time and discrete-time evolutionary dynamical systems applied to empirical games, and scales tractably in the number of agents, in the type of interactions (beyond dyadic), and the type of empirical games (symmetric and asymmetric). Current models are fundamentally limited in one or more of these dimensions, and are not guaranteed to converge to the desired game-theoretic solution concept (typically the Nash equilibrium). α-Rank automatically provides a ranking over the set of agents under evaluation and provides insights into their strengths, weaknesses, and long-term dynamics in terms of basins of attraction and sink components. This is a direct consequence of the correspondence we establish to the dynamical MCC solution concept when the underlying evolutionary model's ranking-intensity parameter, α, is chosen to be large, which exactly forms the basis of α-Rank. In contrast to the Nash equilibrium, which is a static solution concept based solely on fixed points, MCCs are a dynamical solution concept based on the Markov chain formalism, Conley's Fundamental Theorem of Dynamical Systems, and the core ingredients of dynamical systems: fixed points, recurrent sets, periodic orbits, and limit cycles. Our α-Rank method runs in polynomial time with respect to the total number of pure strategy profiles, whereas computing a Nash equilibrium for a general-sum game is known to be intractable. We introduce mathematical proofs that not only provide an overarching and unifying perspective of existing continuous- and discrete-time evolutionary evaluation models, but also reveal the formal underpinnings of the α-Rank methodology. We illustrate the method in canonical games and empirically validate it in several domains, including AlphaGo, AlphaZero, MuJoCo Soccer, and Poker.
- Leaching of elements from cement activated fly ash and slag amended soils. [Journal Article]
- CChemosphere 2019 Jun 26; 235:565-574
- Very few studies have investigated the leaching characteristics of cement activated fly ash and slag treated soils, although the inclusion of cement significantly enhances the material pH and may alt…
Very few studies have investigated the leaching characteristics of cement activated fly ash and slag treated soils, although the inclusion of cement significantly enhances the material pH and may alter the leachability of elements. In this study the leaching behavior and mechanisms of chromium (Cr), copper (Cu), iron (Fe) and sulfur (S) from cement activated fly ash and slag stabilized soils were evaluated. An array of synthetic precipitation leaching procedure (SPLP), batch water leach test (WLT), toxicity characteristic leaching procedure (TCLP) and pH-Static leach tests were conducted. A geochemical equilibrium model Visual MINTEQ was implemented to identify the leaching controlling mechanisms of the metals. Results indicated that, the leached concentrations of Cr, Cu, Fe and S in SPLP, WLT and TCLP effluents were in the range of 0.016-0.74 mg/L, 0.013-0.17 mg/L, 0.019-0.27 mg/L and 1.78-234 mg/L, respectively. Quantitative comparisons between the standard test procedures suggested the necessity of multiple test methods for a comprehensive leaching assessment. Cr and Cu showed amphoteric leaching behaviors, whereas Fe and S followed cationic leaching patterns. According to the geochemical analyses, amorphous Cr(OH)3; tenorite and Cu(OH)2; ferrihydrite and goethite; gypsum and anhydrite; could control the leaching of Cr, Cu, Fe and S, respectively. The effluent Cr concentrations frequently exceeding the U.S. EPA specified maximum contaminant level of 0.1 mg/L. Yet, the use of cement activated fly ash and slag mixed soils could be beneficial, since less toxic trivalent Cr (III) was identified through geochemical modeling.
- Distributional Impacts of Energy-Heat Cross-Subsidization. [Journal Article]
- EPEnergy Policy 2019; 125:65-81
- Energy and heat cross-subsidies are common in developing and transitioning countries, but the distributional and efficiency impacts of these policies (and reform) are largely unknown. In Post-Soviet …
Energy and heat cross-subsidies are common in developing and transitioning countries, but the distributional and efficiency impacts of these policies (and reform) are largely unknown. In Post-Soviet countries such as Belarus, revenues from an industrial tariff on electricity are used to cross-subsidize heating for households. We analyze the distributional impacts of cross-subsidy reform with both input output methods and a calibrated static computable general equilibrium (CGE) model with heterogeneous households based on a household consumption survey. On average, GDP gains of roughly a quarter of a percent are computed across model runs which reduce taxes and subsidies from cross-subsidization. Reducing household heating subsidy rates equally across income groups is found to be regressive. Poorer households are overly-burdened due to higher heating expenditures while richer households enjoy gains from cheaper market prices for goods. The GDP gains are even larger when the tax rates are structured to create a distributionally-neutral reform.
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- [Postural changes in patients with visual deficits]. [Journal Article]
- JFJ Fr Ophtalmol 2019 Jun 28
- CONCLUSIONS: In static equilibrium, patients with poor peripheral vision have better quality somatosensory compensation, but they have a tendency to lean forward, which increases the risk of falling forward. For the three groups, the tests showed that the subjects are vision-dependent, which implies that somatosensory compensation could be developed to limit this dependency. In dynamic equilibrium, the subjects in the disease groups perform significantly worse than the controls. All the visually impaired have a more developed somatosensory mechanism than the controls. The subjects in the first and third groups have the same postural profile, they are vision-dependent. Subjects in the second group have an instability and change in their postural strategy, increasing the risk of falling. Visual acuity has a lesser impact on the risk of falling than the visual field.Comparing postural responses in these different situations, it appears that postural profiles are modified in the case of visual disability, although the postural profile of the group with central visual loss is similar to that of the controls. Retinal involvement, whether central or peripheral, leads to postural imbalance that may result in falls in certain cases. To limit the prevalence of these falls, it would be interesting to address visually impaired patients by examination and postural rehabilitation to decrease the effects of this visual impairment.