175 research outputs found
Letter to the Editor Concerning Simultaneous, Single-Particle Measurements of Size and Loading Give Insights into the Structure of Drug-Delivery Nanoparticles
The vexing error of excess variance in the sizing of single particles
degrades accuracy in applications ranging from quality control of nanoparticle
products to hazard assessment of nanoplastic byproducts. The particular
importance of lipid nanoparticles for vaccine and medicine delivery motivates
this comment on a publication in ACS Nano. In ref 1, the
benchmark measurements of a nanoparticle standard manifest large errors of the
size distribution that contradict the claim of validation. Such errors can bias
the correlation of fluorescence intensity as an optical proxy for the molecular
loading of lipid nanoparticles and give misleading insights from power-law
models of intensitysize data. Looking forward, measurement error models have
the potential to address this widespread issue.Comment: Peer reviewed and pending acceptance by ACS Nan
A lateral nanoflow assay reveals nanoplastic fluorescence heterogeneity
Colloidal nanoplastics present technological opportunities, environmental
concerns, and measurement challenges. To meet these challenges, we develop a
lateral nanoflow assay from sample-in to answer-out. Our measurement system
integrates complex nanofluidic replicas, super-resolution optical microscopy,
and comprehensive statistical analyses to measure polystyrene nanoparticles
that sorb and carry hydrophobic fluorophores. An elegant scaling of surface
forces within our silicone devices hydrodynamically automates the advection and
dominates the diffusion of the nanoparticles. Through steric interaction with
the replica structure, the particle size distribution reciprocally probes the
unknown limits of replica function. Multiple innovations in the integration and
calibration of device and microscope improve the accuracy of identifying single
nanoparticles and quantifying their diameters and fluorescence intensities. A
statistical model of the measurement approaches the information limit of the
system, discriminates size exclusion from surface adsorption, and reduces
nonideal data to return the particle size distribution with nanometer
resolution. A Bayesian statistical analysis of the dimensional and optical
properties of single nanoparticles reveals their fundamental structure-property
relationship. Fluorescence intensity shows a super-volumetric dependence,
scaling with nanoparticle diameter to nearly the fourth power and confounding
basic concepts of chemical sorption. Distributions of fluorescivity - the
product of the number density, absorption cross section, and quantum yield of
an ensemble of fluorophores - are ultrabroad and asymmetric, limiting ensemble
analysis and dimensional or chemical inference from fluorescence intensity.
These results reset expectations for optimizing nanoplastic products,
understanding nanoplastic byproducts, and applying nanoplastic standards
Comparison of Electron-Atom Collision Parameters for S to P Transitions under Reversal of Energy Transfer
Inelastic and superelastic electron scattering from the optically prepared 32P3/2 state of sodium has enabled atomic collision parameters to be deduced for the 4S-3P deexcitation and the 3S-3P excitation processes. These data are compared with convergent close coupling and second order distorted wave Born calculations. For excitation, both theories agree with experiment, whereas for deexcitation the close coupling theory is in better agreement. A long-standing proposal relating to the sign of the transferred angular momentum is not supported
Comparison of Electron-Atom Collision Parameters for S to P Transitions under Reversal of Energy Transfer
Inelastic and superelastic electron scattering from the optically prepared 32P3/2 state of sodium has enabled atomic collision parameters to be deduced for the 4S-3P deexcitation and the 3S-3P excitation processes. These data are compared with convergent close coupling and second order distorted wave Born calculations. For excitation, both theories agree with experiment, whereas for deexcitation the close coupling theory is in better agreement. A long-standing proposal relating to the sign of the transferred angular momentum is not supported
A rapid cell-free expression and screening platform for antibody discovery
Antibody discovery is bottlenecked by the individual expression and evaluation of antigen-specific hits. Here, we address this bottleneck by developing a workflow combining cell-free DNA template generation, cell-free protein synthesis, and binding measurements of antibody fragments in a process that takes hours rather than weeks. We apply this workflow to evaluate 135 previously published antibodies targeting the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), including all 8 antibodies previously granted emergency use authorization for coronavirus disease 2019 (COVID-19), and demonstrate identification of the most potent antibodies. We also evaluate 119 anti-SARS-CoV-2 antibodies from a mouse immunized with the SARS-CoV-2 spike protein and identify neutralizing antibody candidates, including the antibody SC2-3, which binds the SARS-CoV-2 spike protein of all tested variants of concern. We expect that our cell-free workflow will accelerate the discovery and characterization of antibodies for future pandemics and for research, diagnostic, and therapeutic applications more broadly
Sulphur hexaflouride: low energy (e,2e) experiments and molecular three-body distorted wave theory
Experimental and theoretical triple differential ionisation cross-sections (TDCS’s) are presented for the highest occupied molecular orbital of sulphur hexafluoride. These measurements were performed in the low energy regime, with outgoing electron energies ranging from 5 to 40 eV in a coplanar geometry, and with energies of 10 and 20 eV in a perpendicular geometry. Complementary theoretical predictions of the TDCS were calculated using the molecular three-body distorted wave formalism. Calculations were performed using a proper average over molecular orientations as well as the orientation-averaged molecular orbital approximation. This more sophisticated model was found to be in closer agreement with the experimental data, however neither model accurately predicts the TDCS over all geometries and energies
Establishing a distributed national research infrastructure providing bioinformatics support to life science researchers in Australia
EMBL Australia Bioinformatics Resource (EMBL-ABR) is a developing national research infrastructure, providing bioinformatics resources and support to life science and biomedical researchers in Australia. EMBL-ABR comprises 10 geographically distrib- uted national nodes with one coordinating hub, with current funding provided through Bioplatforms Australia and the University of Melbourne for its initial 2-year development phase. The EMBL-ABR mission is to: (1) increase Australia’s capacity in bioinformatics and data sciences; (2) contribute to the development of training in bioinformatics skills; (3) showcase Australian data sets at an international level and (4) enable engagement in international programs. The activities of EMBL-ABR are focussed in six key areas, aligning with comparable international initiatives such as ELIXIR, CyVerse and NIH Commons. These key areas—Tools, Data, Standards, Platforms, Compute and Training—are described in this article
Multi-Messenger Gravitational Wave Searches with Pulsar Timing Arrays: Application to 3C66B Using the NANOGrav 11-year Data Set
When galaxies merge, the supermassive black holes in their centers may form
binaries and, during the process of merger, emit low-frequency gravitational
radiation in the process. In this paper we consider the galaxy 3C66B, which was
used as the target of the first multi-messenger search for gravitational waves.
Due to the observed periodicities present in the photometric and astrometric
data of the source of the source, it has been theorized to contain a
supermassive black hole binary. Its apparent 1.05-year orbital period would
place the gravitational wave emission directly in the pulsar timing band. Since
the first pulsar timing array study of 3C66B, revised models of the source have
been published, and timing array sensitivities and techniques have improved
dramatically. With these advances, we further constrain the chirp mass of the
potential supermassive black hole binary in 3C66B to less than using data from the NANOGrav 11-year data set. This
upper limit provides a factor of 1.6 improvement over previous limits, and a
factor of 4.3 over the first search done. Nevertheless, the most recent orbital
model for the source is still consistent with our limit from pulsar timing
array data. In addition, we are able to quantify the improvement made by the
inclusion of source properties gleaned from electromagnetic data to `blind'
pulsar timing array searches. With these methods, it is apparent that it is not
necessary to obtain exact a priori knowledge of the period of a binary to gain
meaningful astrophysical inferences.Comment: 14 pages, 6 figures. Accepted by Ap
A warm Jet in a cold ocean
Unprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre
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