Active colloidal particles in emulsion droplets: A model system for the cytoplasm

In living cells, molecular motors create activity that enhances the diffusion of particles throughout the cytoplasm, and not just ones attached to the motors. We demonstrate initial steps toward creating artificial cells that mimic this phenomenon. Our system consists of active, Pt-coated Janus particles and passive tracers confined to emulsion droplets. We track the motion of both the active particles and passive tracers in a hydrogen peroxide solution, which serves as the fuel to drive the motion. We first show that correcting for bulk translational and rotational motion of the droplets induced by bubble formation is necessary to accurately track the particles. After drift correction, we find that the active particles show enhanced diffusion in the interior of the droplets and are not captured by the droplet interface. At the particle and hydrogen peroxide concentrations we use, we observe little coupling between the active and passive particles. We discuss the possible reasons for lack of coupling and describe ways to improve the system to more effectively mimic cytoplasmic activity

Mechanisms of viral entry: sneaking in the front door

Recent developments in methods to study virus internalisation are providing clearer insights into mechanisms used by viruses to enter host cells. The use of dominant negative constructs, specific inhibitory drugs and RNAi to selectively prevent entry through particular pathways has provided evidence for the clathrin-mediated entry of hepatitis C virus (HCV) as well as the caveolar entry of Simian Virus 40. Moreover, the ability to image and track fluorescent-labelled virus particles in real-time has begun to challenge the classical plasma membrane entry mechanisms described for poliovirus and human immunodeficiency virus. This review will cover both well-documented entry mechanisms as well as more recent discoveries in the entry pathways of enveloped and non-enveloped viruses. This will include viruses which enter the cytosol directly at the plasma membrane and those which enter via endocytosis and traversal of internal membrane barrier(s). Recent developments in imaging and inhibition of entry pathways have provided insights into the ill-defined entry mechanism of HCV, bringing it to the forefront of viral entry research. Finally, as high-affinity receptors often define viral internalisation pathways, and tropism in vivo, host membrane proteins to which viral particles specifically bind will be discussed throughout

Determinants of penetrance and variable expressivity in monogenic metabolic conditions across 77,184 exomes

Penetrance of variants in monogenic disease and clinical utility of common polygenic variation has not been well explored on a large-scale. Here, the authors use exome sequencing data from 77,184 individuals to generate penetrance estimates and assess the utility of polygenic variation in risk prediction of monogenic variants

Nickel Nanofilms Electrolessly Deposited on Organosilane Nanorings and Characterized by Contact Mode AFM Combined with Magnetic Sample Modulation

Copyright © 2019 American Chemical Society. Surface structures of magnetic nanorings were made using electroless deposition of Ni onto patterned templates of an amine-functionalized organosilane. Samples were prepared by chemical approaches based on colloidal lithography employing a surface mask of size-sorted, monodisperse silica spheres. Surface changes were evaluated after key points of the reactions using imaging modes of atomic force microscopy (AFM). Nanopatterns of 3-aminopropyltriethoxysilane (APTES) were prepared on Si(111) by applying a heated vapor to a surface mask of silica spheres. After rinsing, the particle mask was removed to reveal ring-shaped nanopatterns presenting amine groups at the interface. Organosilane nanopatterns were then immersed in a solution of Pd catalyst followed by treatment in a Ni plating bath. Changes in surface morphology after each reaction step were characterized ex situ using tapping-mode AFM to follow the time course of nanofabrication. Images of the Ni nanorings acquired with AFM were compared with SEM micrographs to further elucidate the morphology of the metal coatings. The magnetic character of the nanostructures was investigated with magnetic sample modulation (MSM-AFM), which is a hybrid of contact mode AFM combined with magnetic actuation of samples. Surface maps of the vibration of diamagnetic Pd and magnetic Ni nanorings were obtained with MSM-AFM, providing insight on processes of electroless plating. Fine details of the surface corrugation and grain structure of the Ni coated areas of the sample detected with SEM were sensitively resolved with MSM-AFM that were not apparent in AFM topography frames. Chemistry-based steps with electroless deposition (ELD) of metal and colloidal lithography provide a practical route for reproducible nanofabrication of highly regular geometries with high-throughput.

Active colloidal particles in emulsion droplets: A model system for the cytoplasm

In living cells, molecular motors create activity that enhances the diffusion of particles throughout the cytoplasm, and not just ones attached to the motors. We demonstrate initial steps toward creating artificial cells that mimic this phenomenon. Our system consists of active, Pt-coated Janus particles and passive tracers confined to emulsion droplets. We track the motion of both the active particles and passive tracers in a hydrogen peroxide solution, which serves as the fuel to drive the motion. We first show that correcting for bulk translational and rotational motion of the droplets induced by bubble formation is necessary to accurately track the particles. After drift correction, we find that the active particles show enhanced diffusion in the interior of the droplets and are not captured by the droplet interface. At the particle and hydrogen peroxide concentrations we use, we observe little coupling between the active and passive particles. We discuss the possible reasons for lack of coupling and describe ways to improve the system to more effectively mimic cytoplasmic activity

A dwarf planet class object in the 21:5 resonance with Neptune

We report the discovery of an Hr = 3.4 ± 0.1 dwarf planet candidate by the Pan-STARRS Outer Solar System Survey. 2010 JO179 is red with (g − r) = 0.88 ± 0.21, roughly round, and slowly rotating, with a period of 30.6 hr. Estimates of its albedo imply a diameter of 600–900 km. Observations sampling the span between 2005 and 2016 provide an exceptionally well determined orbit for 2010 JO179, with a semimajor axis of 78.307 ± 0.009 au; distant orbits known to this precision are rare. We find that 2010 JO179 librates securely within the 21:5 mean-motion resonance with Neptune on 100 Myr timescales, joining the small but growing set of known distant dwarf planets on metastable resonant orbits. These imply a substantial trans-Neptunian population that shifts between stability in high-order resonances, the detached population, and the eroding population of the scattering disk