Search results for "Microscopy"
showing 10 items of 3390 documents
PspA adopts an ESCRT-III-like fold and remodels bacterial membranes
2021
Summary PspA is the main effector of the phage shock protein (Psp) system and preserves the bacterial inner membrane integrity and function. Here, we present the 3.6 A resolution cryoelectron microscopy (cryo-EM) structure of PspA assembled in helical rods. PspA monomers adopt a canonical ESCRT-III fold in an extended open conformation. PspA rods are capable of enclosing lipids and generating positive membrane curvature. Using cryo-EM, we visualized how PspA remodels membrane vesicles into μm-sized structures and how it mediates the formation of internalized vesicular structures. Hotspots of these activities are zones derived from PspA assemblies, serving as lipid transfer platforms and lin…
Advanced fluorescence technologies help to resolve long-standing questions about microbial vitality
2012
International audience; Advances in fundamental physical and optical principles applied to novel fluorescence methods are currently resulting in rapid progress in cell biology and physiology. Instrumentation devised in pioneering laboratories is becoming commercially available, and study findings are now becoming accessible. The first results have concerned mainly higher eukaryotic cells but many more developments can be expected, especially in microbiology. Until now, some important problems of cell physiology have been difficult to investigate due to interactions between probes and cells, excretion of probes from cells and the inability to make in situ observations deep within the cell, w…
Quantification of propagating and standing surface acoustic waves by stroboscopic X-ray photoemission electron microscopy.
2018
The quantification of surface acoustic waves (SAWs) in LiNbO3 piezoelectric crystals by stroboscopic X-ray photoemission electron microscopy (XPEEM), with a temporal smearing below 80 ps and a spatial resolution below 100 nm, is reported. The contrast mechanism is the varying piezoelectric surface potential associated with the SAW phase. Thus, kinetic energy spectra of photoemitted secondary electrons measure directly the SAW electrical amplitude and allow for the quantification of the associated strain. The stroboscopic imaging combined with a deliberate detuning allows resolving and quantifying the respective standing and propagating components of SAWs from a superposition of waves. Furth…
Detecting Protein Aggregation on Cells Surface: Concanavalin A Oligomers Formation
2009
A number of neurodegenerative diseases involve protein aggregation and amyloid formation. Recently evidence has emerged indicating small-transient prefibrillar oligomers as the primary pathogenic agents. Noteworthy, strict analogies exist between the behaviour of cells in culture treated with misfolded non-pathogenic proteins and in pathologic conditions, this instance together with the observation that the oligomers and fibrils are characterised by common structural features suggest that common mechanisms for cytotoxicity could exists and have to be perused in common interactions involved in aggregation.We here report an experimental study on ConcanavalinA (ConA) aggregation and its effect…
Swift light sheet volumetric charting of large human brain portions
2020
Using a custom light sheet fluorescence microscope, we image large stained human brain portions, labelled for NeuN and GAD67 neuronal markers, discerning the inhibitory population via neural-network based image analysis and exposing the brain connectivity.
RNA Nanostructure Molecular Imaging
2020
Atomic force and transmission electron microscopies (AFM/TEM) are powerful tools to analyze RNA-based nanostructures. While cryo-TEM analysis allows the determination of near-atomic resolution structures of large RNA complexes, this chapter intends to present how RNA nanostructures can be analyzed at room temperature on surfaces. Indeed, TEM and AFM analyses permit the conformation of a large population of individual molecular structures to be observed, providing a statistical basis for the variability of these nanostructures within the population. Nevertheless, if double-stranded DNA molecular imaging has been described extensively, only a few investigations of single-stranded DNA and RNA …
Spontaneous domain formation of phospholipase A2 at interfaces: fluorescence microscopy of the interaction of phospholipase A2 with mixed monolayers …
1992
Abstract Fluorescence microscopy has recently been proven to be an ideal tool to investigated the specific interaction of phospholipase A 2 with oriented substrate monolayers. Using a dual labeling technique, it could be shown that phospholipase A 2 can specifically attack and hydrolyze solid analogous l -α-DPPC domains. After a critical extent of monolayer hydrolysis the enzyme itself starts to aggregate forming regular shaped protein domains (Grainger et al. (1990) Biochim. Biophys. Acta 1023. 365–379). In order to confirm that the existence of hydrolysis products in the mononlayer is necessary for the observed aggregation of phospholipase A 2 , mixed monolayers of d - and l -α-DPPC, l -α…
AFM study of interaction forces in supported planar DPPC bilayers in the presence of general anesthetic halothane
2006
International audience; In spite of numerous investigations, the molecular mechanism of general anesthetics action is still not well understood. It has been shown that the anesthetic potency is related to the ability of an anesthetic to partition into the membrane. We have investigated changes in structure, dynamics and forces of interaction in supported dipalmitoylphosphatidylcholine (DPPC) bilayers in the presence of the general anesthetic halothane. In the present study, we measured the forces of interaction between the probe and the bilayer using an atomic force microscope. The changes in force curves as a function of anesthetic incorporation were analyzed. Force measurements were in go…
Direct Observation of Nanometer-Scale Pores of Melittin in Supported Lipid Monolayers
2015
Melittin is the most studied membrane-active peptide and archetype within a large and diverse group of pore formers. However, the molecular characteristics of melittin pores remain largely unknown. Herein, we show by atomic force microscopy (AFM) that lipid monolayers in the presence of melittin are decorated with numerous regularly shaped circular pores that can be distinguished from nonspecific monolayer defects. The specificity of these pores is reinforced through a statistical evaluation of depressions found in Langmuir-Blodgett monolayers in the presence and absence of melittin, which eventually allows characterization of the melittin-induced pores at a quantitative low-resolution leve…
Guidelines for the Direct Detection ofAnaplasmaspp. in Diagnosis and Epidemiological Studies
2017
The genus Anaplasma (Rickettsiales: Anaplasmataceae) comprises obligate intracellular Gram-negative bacteria that are mainly transmitted by ticks, and currently includes six species: Anaplasma bovis, Anaplasma centrale, Anaplasma marginale, Anaplasma phagocytophilum, Anaplasma platys, and Anaplasma ovis. These have long been known as etiological agents of veterinary diseases that affect domestic and wild animals worldwide. A zoonotic role has been recognized for A. phagocytophilum, but other species can also be pathogenic for humans. Anaplasma infections are usually challenging to diagnose, clinically presenting with nonspecific symptoms that vary greatly depending on the agent involved, th…