3,975 research outputs found
Luminescent and Scintillating Properties of Lanthanum Fluoride Nanocrystals in Response to Gamma/Neutron Irradiation: Codoping with Ce Activator, Yb Wavelength Shifter, and Gd Neutron Captor
A novel concept for detection and spectroscopy of gamma rays, and detection
of thermal neutrons based on codoped lanthanum fluoride nanocrystals containing
gadolinium is presented.The trends of colloidal synthesis of the mentioned
material, LaF3 co-doped with Ce as the activator, Yb as the wavelength-shifter
and Gd as the neutron captor, is reported. Nanocrystals of the mentioned
material were characterized by transmission electron microscopy (TEM), X-ray
diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), optical
absorption, and photoluminescence spectroscopy. Gamma detection and its
potential spectroscopy feature have been confirmed. The neutron detection
capability has been confirmed by experiments performed using a 252Cf neutron
source.Comment: 5 figures, 16 page
High-density single-molecule maps reveal transient membrane receptor interactions within a dynamically varying environment
Over recent years, super-resolution and single-molecule imaging methods have
delivered unprecedented details on the nanoscale organization and dynamics of
individual molecules in different contexts. Yet, visualizing single-molecule
processes in living cells with the required spatial and temporal resolution
remains highly challenging. Here, we report on an analytical approach that
extracts such information from live-cell single-molecule imaging at
high-labeling densities using standard fluorescence probes. Our
high-density-mapping (HiDenMap) methodology provides single-molecule nanometric
localization accuracy together with millisecond temporal resolution over
extended observation times, delivering multi-scale spatiotemporal data that
report on the interaction of individual molecules with their dynamic
environment. We validated HiDenMaps by simulations of Brownian trajectories in
the presence of patterns that restrict free diffusion with different
probabilities. We further generated and analyzed HiDenMaps from single-molecule
images of transmembrane proteins having different interaction strengths to
cortical actin, including the transmembrane receptor CD44. HiDenMaps uncovered
a highly heterogenous and multi-scale spatiotemporal organization for all the
proteins that interact with the actin cytoskeleton. Notably, CD44 alternated
between periods of random diffusion and transient trapping, likely resulting
from actin-dependent CD44 nanoclustering. Whereas receptor trapping was dynamic
and lasted for hundreds of milliseconds, actin remodeling occurred at the
timescale of tens of seconds, coordinating the assembly and disassembly of CD44
nanoclusters rich regions. Together, our data demonstrate the power of
HiDenMaps to explore how individual molecules interact with and are organized
by their environment in a dynamic fashion.Comment: 33 pages, 5 figure
XUV Frequency Combs via Femtosecond Enhancement Cavities
We review the current state of tabletop extreme ultraviolet (XUV) sources
based on high harmonic generation (HHG) in femtosecond enhancement cavities
(fsEC). Recent developments have enabled generation of high photon flux (1014
photons/sec) in the XUV, at high repetition rates (>50 MHz) and spanning the
spectral region from 40 nm - 120 nm. This level of performance has enabled
precision spectroscopy with XUV frequency combs and promises further
applications in XUV spectroscopic and photoemission studies. We discuss the
theory of operation and experimental details of the fsEC and XUV generation
based on HHG, including current technical challenges to increasing the photon
flux and maximum photon energy produced by this type of system. Current and
future applications for these sources are also discussed.Comment: invited review article, 38 page
Whi3 mnemon association with endoplasmic reticulum membranes confines the memory of deceptive courtship to the yeast mother cell
Prion-like proteins are involved in many aspects of cellular physiology, including cellular memory. In response to deceptive courtship, budding yeast escapes pheromone-induced cell-cycle arrest through the coalescence of the G1/S inhibitor Whi3 into a dominant, inactive super-assembly. Whi3 is a mnemon (Whi3(mnem)), a protein that conformational change maintains as a trait in the mother cell but is not inherited by the daughter cells. How the maintenance and asymmetric inheritance of Whi3(mnem) are achieved is unknown. Here, we report that Whi3(mnem) is closely associated with endoplasmic reticulum (ER) membranes and is retained in the mother cell by the lateral diffusion barriers present at the bud neck. Strikingly, barrier defects made Whi3(mnem) propagate in a mitotically stable, prion-like manner. The amyloid-forming glutamine-rich domain of Whi3 was required for both mnemon and prion-like behaviors. Thus, we propose that Whi3(mnem) is in a self-templating state, lending temporal maintenance of memory, whereas its association with the compartmentalized membranes of the ER prevents infectious propagation to the daughter cells. These results suggest that confined self-templating super-assembly is a powerful mechanism for the long-term encoding of information in a spatially defined manner. Yeast courtship may provide insights on how individual synapses become potentiated in neuronal memory.Peer reviewe
- …