Electron Spectroscopic Imaging of DNA and Protein-DNA Complexes

1988 ◽  
Vol 46 ◽  
pp. 172-173
Author(s):  
D.P. Bazett-Jones ◽  
M.L. Brown
Keyword(s):  
Transcription Factor ◽  
Transcription Factors ◽  
Electron Microscope ◽  
Spatial Resolution ◽  
Spectroscopic Imaging ◽  
X Rays ◽  
Electron Spectrometer ◽  
Electron Spectroscopic Imaging ◽  
Dna Complexes ◽  
Fixed Beam

Elemental distributions in cells and molecular spreads can now be produced at the spatial resolution attainable in the electron microscope by the collection of X-rays or by the collection of and imaging with inellastically scattered electrons. With the latter method, known as Electron Spectroscopic Imaging (ESI), an image is produced with electrons that have lost characteristic amounts of energy from ionizing or exciting specific elements in the specimen. ESI can generate an elemental map of a specimen at a resolution of about 0.5 nm. It can be carried out in a fixed beam microscope equipped with a parallel energy filter inserted into the column of the microscope below the specimen (1,2). An instrument equipped with a prism-mirror-prism electron spectrometer was used in this study to image purified DNA molecules and a complex of the transcription factor TFIIIA with DNA.Transcription of most genes is activated by the binding of transcription factors to promoter elements.

Comparison of Conventional and Electron Spectroscopic Imaging in the Fixed Beam Electron Microscope of Ordered Protein Arrays

1985 ◽  
Vol 43 ◽  
pp. 74-75
Author(s):  
E. L. Buhle ◽  
U. Aebi
Keyword(s):  
Image Processing ◽  
Electron Microscope ◽  
High Resolution ◽  
Image Plane ◽  
Electron Spectroscopic Imaging ◽  
Protein Arrays ◽  
Beam Electron ◽  
Average Unit ◽  
Fixed Beam ◽  
Energy Components

CTEM brightfield images are formed by a combination of relatively high resolution elastically scattered electrons and unscattered and inelastically scattered electrons. In the case of electron spectroscopic images (ESI), the inelastically scattered electrons cause a loss of both contrast and spatial resolution in the image. In the case of ESI imaging on the Zeiss EM902, the transmited electrons are dispersed into their various energy components by passing them through a magnetic prism spectrometer; a slit is then placed in the image plane of the prism to select the electrons of a given energy loss for image formation. The purpose of this study was to compare CTEM with ESI images recorded on a Zeiss EM902 of ordered protein arrays. Digital image processing was employed to analyze the average unit cell morphologies of the two types of images.

Transcription factor/DNA interactions visualized by electron spectroscopic imaging

1992 ◽  
Vol 50 (1) ◽  
pp. 450-451
Author(s):  
David P. Bazett-Jones ◽  
Mark L. Brown
Keyword(s):  
Transcription Factor ◽  
Dna Sequences ◽  
Transcription Initiation ◽  
Molecular Mechanisms ◽  
Phosphorus Content ◽  
Spectroscopic Imaging ◽  
Electron Spectroscopic Imaging ◽  
Dna Backbone ◽  
Two Parameters ◽  
High Level

A multisubunit RNA polymerase enzyme is ultimately responsible for transcription initiation and elongation of RNA, but recognition of the proper start site by the enzyme is regulated by general, temporal and gene-specific trans-factors interacting at promoter and enhancer DNA sequences. To understand the molecular mechanisms which precisely regulate the transcription initiation event, it is crucial to elucidate the structure of the transcription factor/DNA complexes involved. Electron spectroscopic imaging (ESI) provides the opportunity to visualize individual DNA molecules. Enhancement of DNA contrast with ESI is accomplished by imaging with electrons that have interacted with inner shell electrons of phosphorus in the DNA backbone. Phosphorus detection at this intermediately high level of resolution (≈lnm) permits selective imaging of the DNA, to determine whether the protein factors compact, bend or wrap the DNA. Simultaneously, mass analysis and phosphorus content can be measured quantitatively, using adjacent DNA or tobacco mosaic virus (TMV) as mass and phosphorus standards. These two parameters provide stoichiometric information relating the ratios of protein:DNA content.

scholarly journals SPEEM: The photoemission microscope at the dedicated microfocus PGM beamline UE49-PGMa at BESSY II

2016 ◽  
Vol 2 ◽  
Author(s):  
Florian Kronast ◽  
Sergio Valencia Molina
Keyword(s):  
Electron Microscope ◽  
Electric Field ◽  
Spatial Resolution ◽  
Temperature Control ◽  
Nanometer Scale ◽  
X Rays ◽  
Magnetic Imaging ◽  
Field Temperature ◽  
Photoemission Electron

The UE49-PGMa beamline hosts a photoemission electron microscope (PEEM) dedicated to spectromicroscopy and element-selective magnetic imaging on the nanometer scale. The instrument is an Elmitec PEEM III equipped with energy filter and Helium cooled manipulator. Laser driven excitations can be studied using an attached Ti:Sa laser. A variety of customized sample holders is available for imaging in moderate magnetic / electric field, temperature control, or local laser excitations. With x-rays the instrument is capable of 30 nm spatial resolution.

X-ray detection performance of a 300KV field-emission Analytical Electron Microscope

1993 ◽  
Vol 51 ◽  
pp. 250-251
Author(s):  
C. E. Lyman ◽  
J. I. Goldstein ◽  
D.B. Williams ◽  
D.W. Ackland ◽  
S. von Harrach ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Detection Performance ◽  
Electron Gun ◽  
X Rays ◽  
X Ray ◽  
Analytical Electron ◽  
Analytical Electron Microscope

A major goal of analytical electron micrsocopy (AEM) is to detect small amounts of an element in a given matrix at high spatial resolution. While there is a tradeoff between low detection limit and high spatial resolution, a field emission electron gun allows detection of small amounts of an element at sub-lOnm spatial resolution. The minimum mass fraction of one element measured in another is proportional to [(P/B)·P]-1/2 where the peak-to-background ratio P/B and the peak intensity P both must be high to detect the smallest amount of an element. Thus, the x-ray detection performance of an analytical electron microscope may be characterized in terms of standardized measurements of peak-to-background, x-ray intensity, the level of spurious x-rays (hole count), and x-ray detector performance in terms of energy resolution and peak shape.This paper provides measurements of these parameters from Lehigh’s VG Microscopes HB-603 field emission AEM. This AEM was designed to provide the best x-ray detection possible.

Practical X-ray Spectrometry with Second-Generation Microcalorimeter Detectors

2012 ◽  
Vol 20 (4) ◽  
pp. 38-42 ◽  
Author(s):  
Robin Cantor ◽  
Hideo Naito
Keyword(s):  
Electron Microscope ◽  
Spatial Resolution ◽  
Energy Resolution ◽  
Semiconductor Industry ◽  
High Energy ◽  
High Energy Resolution ◽  
X Rays ◽  
X Ray ◽  
Analytical Technique ◽  
Transmission Electron

X-ray spectroscopy is a widely used and extremely sensitive analytical technique for qualitative as well as quantitative elemental analysis. Typically, high-energy-resolution X-ray spectrometers are integrated with a high-spatial-resolution scanning electron microscope (SEM) or transmission electron microscope (TEM) for X-ray microanalysis applications. The focused electron beam of the SEM or TEM excites characteristic X rays that are emitted by the sample. The integrated X-ray spectrometer can then be used to identify and quantify the elemental composition of the sample on a sub-micron length scale. This combination of energy resolution and spatial resolution makes X-ray microanalysis of great importance to the semiconductor industry.

The contribution of osmium tetroxide to the image quality and detectability of elements in cells studies by electron spectroscopic imaging

1990 ◽  
Vol 48 (3) ◽  
pp. 778-779
Author(s):  
Rebecca C. Stearns ◽  
Cindy L. Hastings ◽  
Marshall Katler ◽  
John J. Godleski
Keyword(s):  
Heavy Metals ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Spectroscopic Imaging ◽  
Electron Spectroscopic Imaging ◽  
Soluble Ions ◽  
The Times ◽  
Fe Ions

Osmium tetroxide has been recognized as an excellent fixative which also contributes to the quality of TEM micrographs (1). In the preparation of biological materials for electron spectroscopic imaging (ESI) of 30 run sections with the Zeiss CEM902 electron microscope, OsO4 is usually used in fixation, but poststaining with heavy metals is not needed. However, the extent of the contribution of OsO4, to the images obtained had not been defined clearly, nor was it clear the extent to which the presence of OsO, might obscure detection of elements by ESI or EELS. To establish optimal liquid fixation for the preservation of soluble ions we monitored the loss of Fe ions during preparation. To determine the role of Os4O, in ESI imaging, hamster alveolar macrophages (AMS) were incubated with 0.ImM FeCLo for 15 minutes, then fixed with 2.5% glutaraldehyde in 0.IM K phosphate buffer in 0.01% CaCLo, then grouped into 6 samples varying the times and percentages of OsO, . One sample was not exposed to any OsO4.

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