2,762 research outputs found
The Influenza M2 Cytoplasmic Tail Changes the Proton-Exchange Equilibria and the Backbone Conformation of the Transmembrane Histidine Residue to Facilitate Proton Conduction
National Institutes of Health (U.S.) (GM088204
Collider search of light dark matter model with dark sector decay
We explore the possibility that the dark matter relic density is not produced
by thermal mechanism directly, but by the decay of other heavier dark sector
particles which on the other hand can be produced by the thermal freeze-out
mechanism. Using a concrete model with a light dark matter from dark sector
decay, we study the collider signature of the dark sector particles in
association with Higgs production processes. We find that the future lepton
colliders can be a better place to probe the signature of this kind of light
dark matter model than the hadron collider such as LHC. Meanwhile, it is found
that a Higgs factory with center of mass energy 250 GeV has a better potential
to resolve the signature of this kind of light dark matter model than the Higgs
factory with center of mass energy 350 GeV.Comment: 15 pages, 14 figure
Re-thinking about Primary and Secondary School Teachersâ Professional Standards in China
China has implemented âMiddle School Teachersâ Professional Standard (trial)â, âPrimary School Teachersâ Professional Standard (trial)â and âKindergarten Teacher Professional Standards (trial)â for over four years. However, in the actual operating level, these teachersâ professional standards have bad influence on teacherâs critical thinking and the alienation relationship between teachers and students, so this article tries to summarize the teachersâ professional standards in developed countries based on the current our country overall education background, and comes up with several suggestions for Teachersâ Professional Standards in China. Keywords: Teachersâ Professional Standards; Education Background; Suggestion
Structural Basis for Asymmetric Conductance of the Influenza M2 Proton Channel Investigated by Solid-State NMR Spectroscopy
The influenza M2 protein forms an acid-activated proton channel that is essential for virus replication. The transmembrane H37 selects for protons under low external pH while W41 ensures proton conduction only from the N terminus to the C terminus and prevents reverse current under low internal pH. Here, we address the molecular basis for this asymmetric conduction by investigating the structure and dynamics of a mutant channel, W41F, which permits reverse current under low internal pH. Solid-state NMR experiments show that W41F M2 retains the pH-dependent α-helical conformations and tetrameric structure of the wild-type (WT) channel but has significantly altered protonation and tautomeric equilibria at H37. At high pH, the H37 structure is shifted toward the Ï tautomer and less cationic tetrads, consistent with faster forward deprotonation to the C terminus. At low pH, the mutant channel contains more cationic tetrads than the WT channel, consistent with faster reverse protonation from the C terminus.15N NMR spectra allow the extraction of four H37 pKas and show that the pKas are more clustered in the mutant channel compared to WT M2. Moreover, binding of the antiviral drug, amantadine, at the N-terminal pore at low pH did not convert all histidines to the neutral state, as seen in WT M2, but left half of all histidines cationic, unambiguously demonstrating C-terminal protonation of H37 in the mutant. These results indicate that asymmetric conduction in WT M2 is due to W41 inhibition of C-terminal acid activation by H37. When Trp is replaced by Phe, protons can be transferred to H37 bidirectionally with distinct rate constants. Keywords:
magic-angle-spinning NMR; tautomeric equilibrium; proton dissociation equilibrium; ion channels; gatingNational Institutes of Health (U.S.) (Grant GM088204
Hyperadrenocorticism of calorie restriction contributes to its antiâinflammatory action in mice
Noninvasive prediction of Blood Lactate through a machine learning-based approach.
We hypothesized that blood lactate concentration([Lac]blood) is a function of cardiopulmonary variables, exercise intensity and some anthropometric elements during aerobic exercise. This investigation aimed to establish a mathematical model to estimate [Lac]blood noninvasively during constant work rate (CWR) exercise of various intensities. 31 healthy participants were recruited and each underwent 4 cardiopulmonary exercise tests: one incremental and three CWR tests (low: 35% of peak work rate for 15âmin, moderate: 60% 10âmin and high: 90% 4âmin). At the end of each CWR test, venous blood was sampled to determine [Lac]blood. 31 trios of CWR tests were employed to construct the mathematical model, which utilized exponential regression combined with Taylor expansion. Good fitting was achieved when the conditions of low and moderate intensity were put in one model; high-intensity in another. Standard deviation of fitting error in the former condition is 0.52; in the latter is 1.82âmmol/liter. Weighting analysis demonstrated that, besides heart rate, respiratory variables are required in the estimation of [Lac]blood in the model of low/moderate intensity. In conclusion, by measuring noninvasive cardio-respiratory parameters, [Lac]blood during CWR exercise can be determined with good accuracy. This should have application in endurance training and future exercise industry
Fever Screening at Airports and Imported Dengue
Airport fever screening in Taiwan, July 2003âJune 2004, identified 40 confirmed dengue cases. Results obtained by capture immunoglobulin (Ig) M and IgG enzyme-linked immunoassay, real time 1-step polymerase chain reaction, and virus isolation showed that 33 (82.5%) of 40 patients were viremic. Airport fever screening can thus quickly identify imported dengue cases
Reconstruction of phyletic trees by global alignment of multiple metabolic networks
Background: In the last decade, a considerable amount of research has been devoted to investigating the phylogenetic properties of organisms from a systems-level perspective. Most studies have focused on the classification of organisms based on structural comparison and local alignment of metabolic pathways. In contrast, global alignment of multiple metabolic networks complements sequence-based phylogenetic analyses and provides more comprehensive information.
Results: We explored the phylogenetic relationships between microorganisms through global alignment of multiple metabolic networks. The proposed approach integrates sequence homology data with topological information of metabolic networks. In general, compared to recent studies, the resulting trees reflect the living style of organisms as well as classical taxa. Moreover, for phylogenetically closely related organisms, the classification results are consistent with specific metabolic characteristics, such as the light-harvesting systems, fermentation types, and sources of electrons in photosynthesis.
Conclusions: We demonstrate the usefulness of global alignment of multiple metabolic networks to infer phylogenetic relationships between species. In addition, our exhaustive analysis of microbial metabolic pathways reveals differences in metabolic features between phylogenetically closely related organisms. With the ongoing increase in the number of genomic sequences and metabolic annotations, the proposed approach will help identify phenotypic variations that may not be apparent based solely on sequence-based classification.National Institutes of Health (U.S.) (Grant GM081871
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