Search results for "ELECTRON MICROSCOPY"

Optical properties of biocompatible polyaniline nano-composites

2006

Abstract Polyaniline (PANI) is an electro-active polymer of great interest thanks to its outstanding physical and chemical properties which make it suitable for various applications in optics, bioelectronics, biosensors, diagnostics and therapeutic devices. Unfortunately, PANI is infusible and insoluble in most common solvents and, thus, very difficult to process. In the attempt of improving processability, yet preserving its interesting properties, PANI has been synthesized in the form of particles and dispersed into a hydrogel matrix. The synthesis of PANI–hydrogel composites proceeds via γ-irradiation of PANI dispersions as obtained by ‘in situ’ polymerization of aniline in the presence …

Peculiarities of imaging one- and two-dimensional structures in an emission electron microscope. 1. theory

2000

Local changes in work function cause deviations of the electrical microfield near a sample surface as a result of the uniform accelerating field distribution between the sample (cathode) and the extractor electrode (anode). This results in a change in the electron trajectories. As a consequence, the microscope image shows remarkable changes in position, size, intensity and lateral resolution of distinct details, which can be quantitatively described by the calculations presented here. Analysing these effects in the image gives an opportunity to determine the real lateral size of the observed structures and the distribution of local contact potentials.

Probing of nanocontacts inside a transmission electron microscope

2007

In the past twenty years, powerful tools such as atomic force microscopy have made it possible to accurately investigate the phenomena of friction and wear, down to the nanometer scale. Readers of this book will become familiar with the concepts and techniques of nanotribology, explained by an international team of scientists and engineers, actively involved and with long experience in this field. Edited by two pioneers in the field, 'Fundamentals of Frictions and Wear at the Nanoscale' is suitable both as first introduction to this fascinating subject, and also as a reference for researchers wishing to improve their knowledge of nanotribology and to keep up with the latest results in this …

Dopant Contrast in Semiconductors as Interpretation Challenge at Imaging by Electrons

2007

Mechanisms responsible for the contrast between differently doped areas in semiconductors, which is observed in electron micrographs, is discussed as regards the key factors determining the sign and magnitude of the contrast. Experimental data obtained by means of the scanning electron microscope (SEM), scanning low energy electron microscope and photoelectron emission microscope are reviewed together with hints following from them for compilation of a model of the contrast mechanism.

The future of transmission electron microscopy (TEM) in biology and medicine.

2000

1996

The uses of atomic force microscopy, scanning tunneling microscopy, electron spectroscopic imaging, electron energy loss spectroscopy and low voltage, high resolution scanning electron microscopy in polymer research are reviewed

Exploiting Cryo-EM Structural Information and All-Atom Simulations To Decrypt the Molecular Mechanism of Splicing Modulators.

2019

Splicing modulators (SMs) pladienolides, herboxidienes, and spliceostatins exert their antitumor activity by altering the ability of SF3B1 and PHF5A proteins, components of SF3b splicing factor, to recognize distinct intron branching point sequences, thus finely calibrating constitutive/alternative/aberrant splicing of pre-mRNA. Here, by exploiting structural information obtained from cryo-EM data, and by performing multiple μs-long all-atom simulations of SF3b in apo form and in complex with selected SMs, we disclose how these latter seep into the narrow slit at the SF3B1/PHF5A protein interface. This locks the intrinsic open/closed conformational transitions of SFB1's solenoidal structure…

3-D reconstruction of hemocyanins and other invertebrate hemolymph proteins by cryo-TEM: an overview.

2004

Three-dimensional structure of hepatitis B virus core particles determined by electron cryomicroscopy

1994

Human hepatitis B virus core protein expressed in E. coli assembles into two sizes of particle. We have determined their three-dimensional structures by electron cryomicroscopy and image processing. The large and small particles correspond to triangulation number T = 4 and T = 3 dimer clustered packings, containing 240 and 180 protein subunits, respectively. The local packing of subunits is very similar in the two sizes of particle and shows holes or channels through the shell. The native viral core particle packages RNA and is active in reverse transcription to DNA. The holes we observe may provide access for the necessary small molecules. Shells assembled from the intact core protein cont…

Structure of the Cryptosporidium parvum microneme: a metabolically and osmotically labile apicomplexan organelle.

2003

From an EM study of thin sections, the rod-like microneme organelles within conventionally glutaraldehyde fixed Cryptosporidium parvum sporozoites have been shown to undergo a shape change to a more spherical structure when the sporozoites age in vitro for a period of approximately 12 to 24 h. This correlates with the shape change of intact sporozoites, from motile hence viable thin banana-shaped cells to swollen pear-shaped cells, shown by differential interference contrast light microscopy of unstained unfixed and glutaraldehyde-fixed samples, as well as by thin section EM of fixed sporozoites. From negatively stained EM specimens of unfixed and fixed sporozoites the cellular shape change…