949 research outputs found
Toward Reproducible Enzyme Modeling with Isothermal Titration Calorimetry
To apply enzymes in technical processes, a detailed understanding of the molecular
mechanisms is required. Kinetic and thermodynamic parameters of enzyme catalysis are
crucial to plan, model, and implement biocatalytic processes more efficiently. While the kinetic
parameters, Km and kcat, are often accessible by optical methods, the determination of
thermodynamic parameters requires more sophisticated methods. Isothermal titration
calorimetry (ITC) allows the label-free and highly sensitive analysis of kinetic and
thermodynamic parameters of individual steps in the catalytic cycle of an enzyme reaction.
However, since ITC is susceptible to interferences due to denaturation or agglomeration of the
enzymes, the homogeneity of the enzyme sample must always be considered, and this can be
accomplished by means of dynamic light scattering (DLS) analysis. The presented ITCdependent
workflow was used to determine both the kinetic and the thermodynamic data for a
cofactor-dependent enzyme. Using a standardized approach with the implementation of
sample quality control by DLS, we obtained high-quality data suitable for the advanced
modeling of the enzyme reaction mechanism. Specifically, we investigated stereoselective
reactions catalyzed by the NADPH-dependent ketoreductase Gre2p under different reaction
conditions. The results revealed that this enzyme operates with an ordered sequential
mechanism in which the cofactor NADPH binds first, resulting in Gre2pholo, and that only
Gre2pholo can then bind the substrate NDK. In addition, the enzyme was found to be affected
by substrate or product inhibition depending on the reaction buffer. Data reproducibility, a
mandatory prerequisite to achieve robust modeling, is ensured by specifying standard
operating procedures, using programmed workflows for data analysis and storing all data in a
F.A.I.R. (findable, accessible, interoperable, and reusable) repository. Our approach highlights
the utility for combined binding and kinetic studies for such complex multisubstrate reactions.
Because it is amenable to automation and scale-up for high-throughput, the combination of
such diverse approaches will provide the high-quality data needed for the engineering of
enzymes and biocatalytic processes through machine learning to accelerate future
development of industrial biocatalysis
Thermodynamics of Strongly Correlated One-Dimensional Bose Gases
We investigate the thermodynamics of one-dimensional Bose gases in the
strongly correlated regime. To this end, we prepare ensembles of independent 1D
Bose gases in a two-dimensional optical lattice and perform high-resolution in
situ imaging of the column-integrated density distribution. Using an inverse
Abel transformation we derive effective one-dimensional line-density profiles
and compare them to exact theoretical models. The high resolution allows for a
direct thermometry of the trapped ensembles. The knowledge about the
temperature enables us to extract thermodynamic equations of state such as the
phase-space density, the entropy per particle and the local pair correlation
function.Comment: 4 pages, 5 figure
Magnetic substructure in the northern Fermi Bubble revealed by polarized WMAP emission
We report a correspondence between giant, polarized microwave structures
emerging north from the Galactic plane near the Galactic center and a number of
GeV gamma-ray features, including the eastern edge of the recently-discovered
northern Fermi Bubble. The polarized microwave features also correspond to
structures seen in the all-sky 408 MHz total intensity data, including the
Galactic center spur. The magnetic field structure revealed by the polarization
data at 23 GHz suggests that neither the emission coincident with the Bubble
edge nor the Galactic center spur are likely to be features of the local ISM.
On the basis of the observed morphological correspondences, similar inferred
spectra, and the similar energetics of all sources, we suggest a direct
connection between the Galactic center spur and the northern Fermi Bubble.Comment: Accepted for publication in The Astrophysical Journal Letters after
minor change
Wild at Heart:-The Particle Astrophysics of the Galactic Centre
We treat of the high-energy astrophysics of the inner ~200 pc of the Galaxy.
Our modelling of this region shows that the supernovae exploding here every few
thousand years inject enough power to i) sustain the steady-state, in situ
population of cosmic rays (CRs) required to generate the region's non-thermal
radio and TeV {\gamma}-ray emis-sion; ii) drive a powerful wind that advects
non-thermal particles out of the inner GC; iii) supply the low-energy CRs whose
Coulombic collisions sustain the temperature and ionization rate of the
anomalously warm, envelope H2 detected throughout the Cen-tral Molecular Zone;
iv) accelerate the primary electrons which provide the extended, non-thermal
radio emission seen over ~150 pc scales above and below the plane (the Galactic
centre lobe); and v) accelerate the primary protons and heavier ions which,
advected to very large scales (up to ~10 kpc), generate the recently-identified
WMAP haze and corresponding Fermi haze/bubbles. Our modelling bounds the
average magnetic field amplitude in the inner few degrees of the Galaxy to the
range 60 < B/microG < 400 (at 2 sigma confidence) and shows that even TeV CRs
likely do not have time to penetrate into the cores of the region's dense
molecular clouds before the wind removes them from the region. This latter
finding apparently disfavours scenarios in which CRs - in this star-burst-like
environment - act to substantially modify the conditions of star-formation. We
speculate that the wind we identify plays a crucial role in advecting
low-energy positrons from the Galactic nucleus into the bulge, thereby
explaining the extended morphology of the 511 keV line emission. (abridged)Comment: One figure corrected. Accepted for publication in MNRAS. 29 pages, 14
figure
ViPR: Visual-Odometry-aided Pose Regression for 6DoF Camera Localization
Visual Odometry (VO) accumulates a positional drift in long-term robot
navigation tasks. Although Convolutional Neural Networks (CNNs) improve VO in
various aspects, VO still suffers from moving obstacles, discontinuous
observation of features, and poor textures or visual information. While recent
approaches estimate a 6DoF pose either directly from (a series of) images or by
merging depth maps with optical flow (OF), research that combines absolute pose
regression with OF is limited. We propose ViPR, a novel modular architecture
for long-term 6DoF VO that leverages temporal information and synergies between
absolute pose estimates (from PoseNet-like modules) and relative pose estimates
(from FlowNet-based modules) by combining both through recurrent layers.
Experiments on known datasets and on our own Industry dataset show that our
modular design outperforms state of the art in long-term navigation tasks.Comment: Conf. on Computer Vision and Pattern Recognition (CVPR): Joint
Workshop on Long-Term Visual Localization, Visual Odometry and Geometric and
Learning-based SLAM 202
Imine Reductase Based All-Enzyme Hydrogel with Intrinsic Cofactor Regeneration for Flow Biocatalysis
All-enzyme hydrogels are biocatalytic materials, with which various enzymes can be immobilized in microreactors in a simple, mild, and efficient manner to be used for continuous flow processes. Here we present the construction and application of a cofactor regenerating hydrogel based on the imine reductase GF3546 from Streptomyces sp. combined with the cofactor regenerating glucose-1-dehydrogenase from Bacillus subtilis. The resulting hydrogel materials were characterized in terms of binding kinetics and viscoelastic properties. The materials were formed by rapid covalent crosslinking in less than 5 min, and they showed a typical mesh size of 67 ± 2 nm. The gels were applied for continuous flow biocatalysis. In a microfluidic reactor setup, the hydrogels showed excellent conversions of imines to amines for up to 40 h in continuous flow mode. Variation of flow rates led to a process where the gels showed a maximum space-time-yield of 150 g·(L·day)−1 at 100 μL/mi
Fusing Structure from Motion and Simulation-Augmented Pose Regression from Optical Flow for Challenging Indoor Environments
The localization of objects is a crucial task in various applications such as
robotics, virtual and augmented reality, and the transportation of goods in
warehouses. Recent advances in deep learning have enabled the localization
using monocular visual cameras. While structure from motion (SfM) predicts the
absolute pose from a point cloud, absolute pose regression (APR) methods learn
a semantic understanding of the environment through neural networks. However,
both fields face challenges caused by the environment such as motion blur,
lighting changes, repetitive patterns, and feature-less structures. This study
aims to address these challenges by incorporating additional information and
regularizing the absolute pose using relative pose regression (RPR) methods.
The optical flow between consecutive images is computed using the Lucas-Kanade
algorithm, and the relative pose is predicted using an auxiliary small
recurrent convolutional network. The fusion of absolute and relative poses is a
complex task due to the mismatch between the global and local coordinate
systems. State-of-the-art methods fusing absolute and relative poses use pose
graph optimization (PGO) to regularize the absolute pose predictions using
relative poses. In this work, we propose recurrent fusion networks to optimally
align absolute and relative pose predictions to improve the absolute pose
prediction. We evaluate eight different recurrent units and construct a
simulation environment to pre-train the APR and RPR networks for better
generalized training. Additionally, we record a large database of different
scenarios in a challenging large-scale indoor environment that mimics a
warehouse with transportation robots. We conduct hyperparameter searches and
experiments to show the effectiveness of our recurrent fusion method compared
to PGO
Benchmarking Visual-Inertial Deep Multimodal Fusion for Relative Pose Regression and Odometry-aided Absolute Pose Regression
Visual-inertial localization is a key problem in computer vision and robotics
applications such as virtual reality, self-driving cars, and aerial vehicles.
The goal is to estimate an accurate pose of an object when either the
environment or the dynamics are known. Recent methods directly regress the pose
using convolutional and spatio-temporal networks. Absolute pose regression
(APR) techniques predict the absolute camera pose from an image input in a
known scene. Odometry methods perform relative pose regression (RPR) that
predicts the relative pose from a known object dynamic (visual or inertial
inputs). The localization task can be improved by retrieving information of
both data sources for a cross-modal setup, which is a challenging problem due
to contradictory tasks. In this work, we conduct a benchmark to evaluate deep
multimodal fusion based on PGO and attention networks. Auxiliary and Bayesian
learning are integrated for the APR task. We show accuracy improvements for the
RPR-aided APR task and for the RPR-RPR task for aerial vehicles and hand-held
devices. We conduct experiments on the EuRoC MAV and PennCOSYVIO datasets, and
record a novel industry dataset.Comment: Under revie
Molecular response of Deinococcus radiodurans to simulated microgravity explored by proteometabolomic approach
Regarding future space exploration missions and long-term exposure experiments, a detailed
investigation of all factors present in the outer space environment and their effects on organisms of
all life kingdoms is advantageous. Influenced by the multiple factors of outer space, the extremophilic
bacterium Deinococcus radiodurans has been long-termly exposed outside the international Space
Station in frames of the tanpopo orbital mission. the study presented here aims to elucidate molecular
key components in D. radiodurans, which are responsible for recognition and adaptation to simulated
microgravity. D. radiodurans cultures were grown for two days on plates in a fast-rotating 2-D clinostat
to minimize sedimentation, thus simulating reduced gravity conditions. Subsequently, metabolites
and proteins were extracted and measured with mass spectrometry-based techniques. our results
emphasize the importance of certain signal transducer proteins, which showed higher abundances
in cells grown under reduced gravity. these proteins activate a cellular signal cascade, which leads to
differences in gene expressions. Proteins involved in stress response, repair mechanisms and proteins
connected to the extracellular milieu and the cell envelope showed an increased abundance under
simulated microgravity. focusing on the expression of these proteins might present a strategy of cells
to adapt to microgravity conditions
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