Bipolar extraction neutralization: Time resolved characterization

2000 ◽  
Vol 71 (2) ◽  
pp. 1090-1093 ◽  
Author(s):  
D. Korzec ◽  
R. Dahlhaus ◽  
J. Engemann
Keyword(s):  
Time Resolved ◽  
Neutralization Time

Microtubule nucleation sequence studied by time-resolved x-ray scattering and electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 766-767
Author(s):  
Eva-Maria Mandelkow ◽  
Eckhard Mandelkow ◽  
Joan Bordas
Keyword(s):  
Electron Microscopy ◽  
Dynamic Equilibrium ◽  
Time Resolved ◽  
X Ray ◽  
Additional Information ◽  
X Ray Scattering ◽  
Low Concentrations ◽  
Microtubule Growth ◽  
Ray Patterns ◽  
Ray Scattering

When a solution of microtubule protein is changed from non-polymerising to polymerising conditions (e.g. by temperature jump or mixing with GTP) there is a series of structural transitions preceding microtubule growth. These have been detected by time-resolved X-ray scattering using synchrotron radiation, and they may be classified into pre-nucleation and nucleation events. X-ray patterns are good indicators for the average behavior of the particles in solution, but they are difficult to interpret unless additional information on their structure is available. We therefore studied the assembly process by electron microscopy under conditions approaching those of the X-ray experiment. There are two difficulties in the EM approach: One is that the particles important for assembly are usually small and not very regular and therefore tend to be overlooked. Secondly EM specimens require low concentrations which favor disassembly of the particles one wants to observe since there is a dynamic equilibrium between polymers and subunits.

Electron Channeling Patterns

1977 ◽  
Vol 35 ◽  
pp. 12-13
Author(s):  
David C. Joy
Keyword(s):  
Electron Diffraction ◽  
Incidence Angle ◽  
Photographic Plate ◽  
Diffraction Effect ◽  
Angle Of Incidence ◽  
Bulk Single Crystal ◽  
Time Resolved ◽  
Electron Channeling ◽  
Spatially Resolved ◽  
Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

Time-resolved high-resolution electron microscopy of structural stability in mgo clusters

1996 ◽  
Vol 54 ◽  
pp. 672-673
Author(s):  
T. Kizuka ◽  
N. Tanaka
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Magnesium Oxide ◽  
Structural Stability ◽  
High Resolution Electron Microscopy ◽  
Video Tape ◽  
Solid State Physics ◽  
Time Resolved ◽  
Resolution Electron ◽  
Structural And Functional Properties

Structure and stability of atomic clusters have been studied by time-resolved high-resolution electron microscopy (TRHREM). Typical examples are observations of structural fluctuation in gold (Au) clusters supported on silicon oxide films, graphtized carbon films and magnesium oxide (MgO) films. All the observations have been performed on the clusters consisted of single metal element. Structural stability of ceramics clusters, such as metal-oxide, metal-nitride and metal-carbide clusters, has not been observed by TRHREM although the clusters show anomalous structural and functional properties concerning to solid state physics and materials science.In the present study, the behavior of ceramic, magnesium oxide (MgO) clusters is for the first time observed by TRHREM at 1/60 s time resolution and at atomic resolution down to 0.2 nm.MgO and gold were subsequently deposited on sodium chloride (001) substrates. The specimens, single crystalline MgO films on which Au particles were dispersed were separated in distilled water and observed by using a 200-kV high-resolution electron microscope (JEOL, JEM2010) equipped with a high sensitive TV camera and a video tape recorder system.

Cryo-TEM of amphiphilic polymer and amphiphile/polymer solutions

1993 ◽  
Vol 51 ◽  
pp. 876-877
Author(s):  
Yeshayahu Talmon
Keyword(s):  
Microstructural Characterization ◽  
Building Blocks ◽  
Quantitative Information ◽  
Physical Models ◽  
Specimen Preparation ◽  
Time Resolved ◽  
Temperature Changes ◽  
Temperature And Humidity ◽  
Microstructured Fluids ◽  
Air Streams

To achieve complete microstructural characterization of self-aggregating systems, one needs direct images in addition to quantitative information from non-imaging, e.g., scattering or Theological measurements, techniques. Cryo-TEM enables us to image fluid microstructures at better than one nanometer resolution, with minimal specimen preparation artifacts. Direct images are used to determine the “building blocks” of the fluid microstructure; these are used to build reliable physical models with which quantitative information from techniques such as small-angle x-ray or neutron scattering can be analyzed.To prepare vitrified specimens of microstructured fluids, we have developed the Controlled Environment Vitrification System (CEVS), that enables us to prepare samples under controlled temperature and humidity conditions, thus minimizing microstructural rearrangement due to volatile evaporation or temperature changes. The CEVS may be used to trigger on-the-grid processes to induce formation of new phases, or to study intermediate, transient structures during change of phase (“time-resolved cryo-TEM”). Recently we have developed a new CEVS, where temperature and humidity are controlled by continuous flow of a mixture of humidified and dry air streams.

The promises and perfidy of cryomicroscopy and analysis

1994 ◽  
Vol 52 ◽  
pp. 382-383
Author(s):  
Patrick Echlin
Keyword(s):  
Low Temperature ◽  
High Energy ◽  
Short Paper ◽  
List Type ◽  
Time Resolved ◽  
Energy Beam ◽  
Cellular Analysis ◽  
Dissolved Ions ◽  
Embedding Medium ◽  
Low Temperature Microscopy

The unusual title of this short paper and its accompanying tutorial is deliberate, because the intent is to investigate the effectiveness of low temperature microscopy and analysis as one of the more significant elements of the less interventionist procedures we can use to prepare, examine and analyse hydrated and organic materials in high energy beam instruments. The promises offered by all these procedures are well rehearsed and the litany of petitions and responses may be enunciated in the following mantra.Vitrified water can form the perfect embedding medium for bio-organic samples.Frozen samples provide an important, but not exclusive, milieu for the in situ sub-cellular analysis of the dissolved ions and electrolytes whose activities are central to living processes.The rapid conversion of liquids to solids provides a means of arresting dynamic processes and permits resolution of the time resolved interactions between water and suspended and dissolved materials.The low temperature environment necessary for cryomicroscopy and analysis, diminish, but alas do not prevent, the deleterious side effects of ionizing radiation.Sample contamination is virtually eliminated.

Electron-beam damage of oxides at high current densities

1989 ◽  
Vol 47 ◽  
pp. 634-635
Author(s):  
M. R. McCartney ◽  
J. K. Weiss ◽  
David J. Smith
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Current Density ◽  
Transition Metal Oxides ◽  
Time Resolved ◽  
Rapid Acquisition ◽  
Resolution Electron ◽  
Current Densities ◽  
Electron Stimulated Desorption ◽  
Channel Analyzer

It is well-known that electron-beam irradiation within the electron microscope can induce a variety of surface reactions. In the particular case of maximally-valent transition-metal oxides (TMO), which are susceptible to electron-stimulated desorption (ESD) of oxygen, it is apparent that the final reduced product depends, amongst other things, upon the ionicity of the original oxide, the energy and current density of the incident electrons, and the residual microscope vacuum. For example, when TMO are irradiated in a high-resolution electron microscope (HREM) at current densities of 5-50 A/cm2, epitaxial layers of the monoxide phase are found. In contrast, when these oxides are exposed to the extreme current density probe of an EM equipped with a field emission gun (FEG), the irradiated area has been reported to develop either holes or regions almost completely depleted of oxygen. ’ In this paper, we describe the responses of three TMO (WO3, V2O5 and TiO2) when irradiated by the focussed probe of a Philips 400ST FEG TEM, also equipped with a Gatan 666 Parallel Electron Energy Loss Spectrometer (P-EELS). The multi-channel analyzer of the spectrometer was modified to take advantage of the extremely rapid acquisition capabilities of the P-EELS to obtain time-resolved spectra of the oxides during the irradiation period. After irradiation, the specimens were immediately removed to a JEM-4000EX HREM for imaging of the damaged regions.

Multiple phase transitions investigated by high-speed TEM

1990 ◽  
Vol 48 (4) ◽  
pp. 550-551
Author(s):  
Oleg Bostanjoglo ◽  
Peter Thomsen-Schmidt
Keyword(s):  
Phase Transitions ◽  
High Speed ◽  
Short Exposure ◽  
Semiconductor Film ◽  
Time Resolved ◽  
Short Exposure Time ◽  
Multiple Phase ◽  
Model Substance ◽  
History Of ◽  
Electron Image

Thin GexTe1-x (x = 0.15-0.8) were studied as a model substance of a composite semiconductor film, in addition being of interest for optical storage material. Two complementary modes of time-resolved TEM were used to trace the phase transitions, induced by an attached Q-switched (50 ns FWHM) and frequency doubled (532 nm) Nd:YAG laser. The laser radiation was focused onto the specimen within the TEM to a 20 μm spot (FWHM). Discrete intermediate states were visualized by short-exposure time doubleframe imaging /1,2/. The full history of a transformation was gained by tracking the electron image intensity with photomultiplier and storage oscilloscopes (space/time resolution 100 nm/3 ns) /3/. In order to avoid radiation damage by the probing electron beam to detector and specimen, the beam is pulsed in this continuous mode of time-resolved TEM,too.Short events ( <2 μs) are followed by illuminating with an extended single electron pulse (fig. 1c)

Time-Resolved Cryo-Electron Microscopy of Oscillating Microtubules

1990 ◽  
Vol 48 (1) ◽  
pp. 502-503
Author(s):  
Eva-Maria Mandelkow ◽  
Ron Milligan
Keyword(s):  
Electron Microscopy ◽  
Dynamic Instability ◽  
Entire Solution ◽  
Reaction Scheme ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
A Chain ◽  
Ray Scattering

Microtubules form part of the cytoskeleton of eukaryotic cells. They are hollow libers of about 25 nm diameter made up of 13 protofilaments, each of which consists of a chain of heterodimers of α-and β-tubulin. Microtubules can be assembled in vitro at 37°C in the presence of GTP which is hydrolyzed during the reaction, and they are disassembled at 4°C. In contrast to most other polymers microtubules show the behavior of “dynamic instability”, i.e. they can switch between phases of growth and phases of shrinkage, even at an overall steady state [1]. In certain conditions an entire solution can be synchronized, leading to autonomous oscillations in the degree of assembly which can be observed by X-ray scattering (Fig. 1), light scattering, or electron microscopy [2-5]. In addition such solutions are capable of generating spontaneous spatial patterns [6].In an earlier study we have analyzed the structure of microtubules and their cold-induced disassembly by cryo-EM [7]. One result was that disassembly takes place by loss of protofilament fragments (tubulin oligomers) which fray apart at the microtubule ends. We also looked at microtubule oscillations by time-resolved X-ray scattering and proposed a reaction scheme [4] which involves a cyclic interconversion of tubulin, microtubules, and oligomers (Fig. 2). The present study was undertaken to answer two questions: (a) What is the nature of the oscillations as seen by time-resolved cryo-EM? (b) Do microtubules disassemble by fraying protofilament fragments during oscillations at 37°C?

Structural dynamics of P-type ATPase ion pumps

2019 ◽  
Vol 47 (5) ◽  
pp. 1247-1257 ◽  
Author(s):  
Mateusz Dyla ◽  
Sara Basse Hansen ◽  
Poul Nissen ◽  
Magnus Kjaergaard
Keyword(s):  
Structural Dynamics ◽  
Single Molecule ◽  
New Technologies ◽  
Atp Hydrolysis ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Time Resolved ◽  
Dynamics Simulations ◽  
Types Of Information ◽  
P Type

Abstract P-type ATPases transport ions across biological membranes against concentration gradients and are essential for all cells. They use the energy from ATP hydrolysis to propel large intramolecular movements, which drive vectorial transport of ions. Tight coordination of the motions of the pump is required to couple the two spatially distant processes of ion binding and ATP hydrolysis. Here, we review our current understanding of the structural dynamics of P-type ATPases, focusing primarily on Ca2+ pumps. We integrate different types of information that report on structural dynamics, primarily time-resolved fluorescence experiments including single-molecule Förster resonance energy transfer and molecular dynamics simulations, and interpret them in the framework provided by the numerous crystal structures of sarco/endoplasmic reticulum Ca2+-ATPase. We discuss the challenges in characterizing the dynamics of membrane pumps, and the likely impact of new technologies on the field.

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