946 research outputs found
Using online exemplars as a critical intersection: Moving from generic to discipline-specific writing at the university
Mechanochemical Coupling in the Myosin Motor Domain. I. Insights from Equilibrium Active-Site Simulations
Although the major structural transitions in molecular motors are often argued to couple to the binding of Adenosine triphosphate (ATP), the recovery stroke in the conventional myosin has been shown to be dependent on the hydrolysis of ATP. To obtain a clearer mechanistic picture for such âmechanochemical couplingâ in myosin, equilibrium active-site simulations with explicit solvent have been carried out to probe the behavior of the motor domain as functions of the nucleotide chemical state and conformation of the converter/relay helix. In conjunction with previous studies of ATP hydrolysis with different active-site conformations and normal mode analysis of structural flexibility, the results help establish an energetics-based framework for understanding the mechanochemical coupling. It is proposed that the activation of hydrolysis does not require the rotation of the lever arm per se, but the two processes are tightly coordinated because both strongly couple to the open/close transition of the active site. The underlying picture involves shifts in the dominant population of different structural motifs as a consequence of changes elsewhere in the motor domain. The contribution of this work and the accompanying paper [36] is to propose the actual mechanism behind these âpopulation shiftsâ and residues that play important roles in the process. It is suggested that structural flexibilities at both the small and large scales inherent to the motor domain make it possible to implement tight couplings between different structural motifs while maintaining small free-energy drops for processes that occur in the detached states, which is likely a feature shared among many molecular motors. The significantly different flexibility of the active site in different X-ray structures with variable level arm orientations supports the notation that external force sensed by the lever arm may transmit into the active site and influence the chemical steps (nucleotide hydrolysis and/or binding)
Service-learning and research scheme : the Lingnan model
This Manual is a product of Lingnan Universityâs pilot SLRS. It aims to provide a framework for interested parties to organize or refine a range of Service-Learning
Programs and to develop a comprehensive set of validating instruments that can be used to assess the effectiveness of the SLRS from the varying perspectives of students, course instructors, social service agency supervisors and program coordinators. The specific objectives of this Manual are:
(i) To provide useful reference information on Service-Learning to interested parties at Lingnan University and other tertiary institutions.
(ii) To provide definitions of the structures, contents and processes of the Lingnan model of Service-Learning (SLRS) and guidance to support implementation.
(iii) To provide a set of validation instruments, as developed by Lingnan, for evaluating the effectiveness of the SLRS from the perspective of participants.
(iv) To share the summary results of the evaluation of Lingnanâs SLRS pilot.
This is the first manual of its kind for running a Service-Learning scheme with the unique characteristics of liberal arts education in Hong Kong.https://commons.ln.edu.hk/osl_book/1004/thumbnail.jp
MIRA: Mental Imagery for Robotic Affordances
Humans form mental images of 3D scenes to support counterfactual imagination,
planning, and motor control. Our abilities to predict the appearance and
affordance of the scene from previously unobserved viewpoints aid us in
performing manipulation tasks (e.g., 6-DoF kitting) with a level of ease that
is currently out of reach for existing robot learning frameworks. In this work,
we aim to build artificial systems that can analogously plan actions on top of
imagined images. To this end, we introduce Mental Imagery for Robotic
Affordances (MIRA), an action reasoning framework that optimizes actions with
novel-view synthesis and affordance prediction in the loop. Given a set of 2D
RGB images, MIRA builds a consistent 3D scene representation, through which we
synthesize novel orthographic views amenable to pixel-wise affordances
prediction for action optimization. We illustrate how this optimization process
enables us to generalize to unseen out-of-plane rotations for 6-DoF robotic
manipulation tasks given a limited number of demonstrations, paving the way
toward machines that autonomously learn to understand the world around them for
planning actions.Comment: CoRL 2022, webpage: https://yenchenlin.me/mir
EcoTILLING for the identification of allelic variants of melon eIF4E, a factor that controls virus susceptibility
<p>Abstract</p> <p>Background</p> <p>Translation initiation factors of the 4E and 4G protein families mediate resistance to several RNA plant viruses in the natural diversity of crops. Particularly, a single point mutation in melon eukaryotic translation initiation factor 4E (eIF4E) controls resistance to <it>Melon necrotic spot virus </it>(MNSV) in melon. Identification of allelic variants within natural populations by EcoTILLING has become a rapid genotype discovery method.</p> <p>Results</p> <p>A collection of <it>Cucumis </it>spp. was characterised for susceptibility to MNSV and <it>Cucumber vein yellowing virus </it>(CVYV) and used for the implementation of EcoTILLING to identify new allelic variants of <it>eIF4E</it>. A high conservation of <it>eIF4E </it>exonic regions was found, with six polymorphic sites identified out of EcoTILLING 113 accessions. Sequencing of regions surrounding polymorphisms revealed that all of them corresponded to silent nucleotide changes and just one to a non-silent change correlating with MNSV resistance. Except for the MNSV case, no correlation was found between variation of eIF4E and virus resistance, suggesting the implication of different and/or additional genes in previously identified resistance phenotypes. We have also characterized a new allele of <it>eIF4E </it>from <it>Cucumis zeyheri</it>, a wild relative of melon. Functional analyses suggested that this new <it>eIF4E </it>allele might be responsible for resistance to MNSV.</p> <p>Conclusion</p> <p>This study shows the applicability of EcoTILLING in <it>Cucumis </it>spp., but given the conservation of eIF4E, new candidate genes should probably be considered to identify new sources of resistance to plant viruses. Part of the methodology described here could alternatively be used in TILLING experiments that serve to generate new <it>eIF4E </it>alleles.</p
A 50-Year-Old Woman with Recurrent Generalised Seizures
Ronald Ma and colleagues discuss the differential diagnosis, investigation, and management of this patient
Robustness of circadian clocks to daylight fluctuations: hints from the picoeucaryote Ostreococcus tauri
The development of systemic approaches in biology has put emphasis on
identifying genetic modules whose behavior can be modeled accurately so as to
gain insight into their structure and function. However most gene circuits in a
cell are under control of external signals and thus quantitative agreement
between experimental data and a mathematical model is difficult. Circadian
biology has been one notable exception: quantitative models of the internal
clock that orchestrates biological processes over the 24-hour diurnal cycle
have been constructed for a few organisms, from cyanobacteria to plants and
mammals. In most cases, a complex architecture with interlocked feedback loops
has been evidenced. Here we present first modeling results for the circadian
clock of the green unicellular alga Ostreococcus tauri. Two plant-like clock
genes have been shown to play a central role in Ostreococcus clock. We find
that their expression time profiles can be accurately reproduced by a minimal
model of a two-gene transcriptional feedback loop. Remarkably, best adjustment
of data recorded under light/dark alternation is obtained when assuming that
the oscillator is not coupled to the diurnal cycle. This suggests that coupling
to light is confined to specific time intervals and has no dynamical effect
when the oscillator is entrained by the diurnal cycle. This intringuing
property may reflect a strategy to minimize the impact of fluctuations in
daylight intensity on the core circadian oscillator, a type of perturbation
that has been rarely considered when assessing the robustness of circadian
clocks
Macrophage CGI-58 Deficiency Activates ROS-Inflammasome Pathway to Promote Insulin Resistance in Mice
SummaryOvernutrition activates a proinflammatory program in macrophages to induce insulin resistance (IR), but its molecular mechanisms remain incompletely understood. Here, we show that saturated fatty acid and lipopolysaccharide, two factors implicated in high-fat diet (HFD)-induced IR, suppress macrophage CGI-58 expression. Macrophage-specific CGI-58 knockout (MaKO) in mice aggravates HFD-induced glucose intolerance and IR, which is associated with augmented systemic/tissue inflammation and proinflammatory activation of adipose tissue macrophages. CGI-58-deficient macrophages exhibit mitochondrial dysfunction due to defective peroxisome proliferator-activated receptor (PPAR)Îł signaling. Consequently, they overproduce reactive oxygen species (ROS) to potentiate secretion of proinflammatory cytokines by activating NLRP3 inflammasome. Anti-ROS treatment or NLRP3 silencing prevents CGI-58-deficient macrophages from oversecreting proinflammatory cytokines and from inducing proinflammatory signaling and IR in the cocultured fat slices. Anti-ROS treatment also prevents exacerbation of inflammation and IR in HFD-fed MaKO mice. Our data thus establish CGI-58 as a suppressor of overnutrition-induced NLRP3 inflammasome activation in macrophages
Astrocytic Ion Dynamics: Implications for Potassium Buffering and Liquid Flow
We review modeling of astrocyte ion dynamics with a specific focus on the
implications of so-called spatial potassium buffering, where excess potassium
in the extracellular space (ECS) is transported away to prevent pathological
neural spiking. The recently introduced Kirchoff-Nernst-Planck (KNP) scheme for
modeling ion dynamics in astrocytes (and brain tissue in general) is outlined
and used to study such spatial buffering. We next describe how the ion dynamics
of astrocytes may regulate microscopic liquid flow by osmotic effects and how
such microscopic flow can be linked to whole-brain macroscopic flow. We thus
include the key elements in a putative multiscale theory with astrocytes
linking neural activity on a microscopic scale to macroscopic fluid flow.Comment: 27 pages, 7 figure
Size and surface charge of gold nanoparticles determine absorption across intestinal barriers and accumulation in secondary target organs after oral administration
It is of urgent need to identify the exact physico-chemical characteristics which allow maximum uptake and accumulation in secondary target organs of nanoparticulate drug delivery systems after oral ingestion. We administered radiolabelled gold nanoparticles in different sizes (1.4-200 nm) with negative surface charge and 2.8 nm nanoparticles with opposite surface charges by intra-oesophageal instillation into healthy adult female rats. The quantitative amount of the particles in organs, tissues and excrements was measured after 24 h by gamma-spectroscopy. The highest accumulation in secondary organs was mostly found for 1.4 nm particles; the negatively charged particles were accumulated mostly more than positively charged particles. Importantly, 18 nm particles show a higher accumulation in brain and heart compared to other sized particles. No general rule accumulation can be made so far. Therefore, specialized drug delivery systems via the oral route have to be individually designed, depending on the respective target organ
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