scholarly journals Quantification of nanoscale density fluctuations using electron microscopy: Light-localization properties of biological cells

2010 ◽  
Vol 97 (24) ◽  
pp. 243704 ◽  
Author(s):  
Prabhakar Pradhan ◽  
Dhwanil Damania ◽  
Hrushikesh M. Joshi ◽  
Vladimir Turzhitsky ◽  
Hariharan Subramanian ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Density Fluctuations ◽  
Biological Cells ◽  
Light Localization

scholarly journals Fracture faces of frozen membranes: 50th anniversary

2016 ◽  
Vol 27 (3) ◽  
pp. 421-423
Author(s):  
Daniel Branton
Keyword(s):  
Electron Microscopy ◽  
Lipid Bilayers ◽  
Fracture Process ◽  
Relative Proportion ◽  
50Th Anniversary ◽  
Biological Membranes ◽  
Bilayer Membrane ◽  
Biological Cells ◽  
Membrane Surfaces ◽  
Freeze Etching

In 1961, the development of an improved freeze-etching (FE) procedure to prepare rapidly frozen biological cells or tissues for electron microscopy raised two important questions. How does a frozen cell membrane fracture? What do the extensive face views of the cell’s membranes exposed by the fracture process of FE tell us about the overall structure of biological membranes? I discovered that all frozen membranes tend to split along weakly bonded lipid bilayers. Consequently, the fracture process exposes internal membrane faces rather than either of the membrane’s two external surfaces. During etching, when ice is allowed to sublime after fracturing, limited regions of the actual membrane surfaces are revealed. Examination of the fractured faces and etched surfaces provided strong evidence that biological membranes are organized as lipid bilayers with some proteins on the surface and other proteins extending through the bilayer. Membrane splitting made it possible for electron microscopy to show the relative proportion of a membrane’s area that exists in either of these two organizational modes.

scholarly journals Quantification of nanoscale density fluctuations by electron microscopy: probing cellular alterations in early carcinogenesis

2011 ◽  
Vol 8 (2) ◽  
pp. 026012 ◽  
Author(s):  
Prabhakar Pradhan ◽  
Dhwanil Damania ◽  
Hrushikesh M Joshi ◽  
Vladimir Turzhitsky ◽  
Hariharan Subramanian ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Density Fluctuations ◽  
Early Carcinogenesis ◽  
Cellular Alterations

scholarly journals A comparison of absorption and phase contrast for X-ray imaging of biological cells

2018 ◽  
Vol 25 (5) ◽  
pp. 1490-1504 ◽  
Author(s):  
Colin Nave
Keyword(s):  
Electron Microscopy ◽  
Phase Contrast ◽  
Statistical Significance ◽  
Refractive Indices ◽  
Biological Cells ◽  
X Ray ◽  
Water Window ◽  
X Ray Imaging ◽  
Cellular Components ◽  
Absorption Contrast

X-ray imaging allows biological cells to be examined at a higher resolution than possible with visible light and without some of the preparation difficulties associated with electron microscopy of thick samples. The most used and developed technique is absorption contrast imaging in the water window which exploits the contrast between carbon and oxygen at an energy of around 500 eV. A variety of phase contrast techniques are also being developed. In general these operate at a higher energy, enabling thicker cells to be examined and, in some cases, can be combined with X-ray fluorescence imaging to locate specific metals. The various methods are based on the differences between the complex refractive indices of the cellular components and the surrounding cytosol or nucleosol, the fluids present in the cellular cytoplasm and nucleus. The refractive indices can be calculated from the atomic composition and density of the components. These in turn can be obtained from published measurements using techniques such as chemical analysis, scanning electron microscopy and X-ray imaging at selected energies. As examples, the refractive indices of heterochromatin, inner mitochondrial membranes, the neutral core of lipid droplets, starch granules, cytosol and nucleosol are calculated. The refractive index calculations enable the required doses and fluences to be obtained to provide images with sufficient statistical significance, for X-ray energies between 200 and 4000 eV. The statistical significance (e.g. the Rose criterion) for various requirements is discussed. The calculations reveal why some cellular components are more visible by absorption contrast and why much greater exposure times are required to see some cellular components. A comparison of phase contrast as a function of photon energy with absorption contrast in the water window is provided and it is shown that much higher doses are generally required for the phase contrast measurements. This particularly applies to those components with a high carbon content but with a mass density similar to the surrounding cytosol or nucleosol. The results provide guidance for the most appropriate conditions for X-ray imaging of individual cellular components within cells of various thicknesses.

Cryo-electron microscopy of vitreous sections of native biological cells and tissues

2004 ◽  
Vol 148 (1) ◽  
pp. 131-135 ◽  
Author(s):  
Ashraf Al-Amoudi ◽  
Lars P.O. Norlen ◽  
Jacques Dubochet
Keyword(s):  
Electron Microscopy ◽  
Biological Cells ◽  
Cryo Electron Microscopy

scholarly journals Микрофазовое разделение в имидсилоксановом сополимере

2019 ◽  
Vol 61 (7) ◽  
pp. 1391
Author(s):  
Д.В. Новиков ◽  
В.М. Светличный ◽  
А.А. Мартыненков
Keyword(s):  
Electron Microscopy ◽  
Comparative Analysis ◽  
Block Copolymer ◽  
Long Range ◽  
Surface Texture ◽  
Microphase Separation ◽  
Density Fluctuations ◽  
Long Range Order ◽  
Axial Texture ◽  
Spatially Oriented

By means of electron microscopy, a comparative analysis of the micro-inhomogeneous structure of the surface of films of amorphous aromatic polyetherimide — poly{4,4'-bis[(4''-N-phenoxy) diphenylsulfone] imide 1,3-bis (3',4-dicarboxyphenoxy) benzene} (PEI) - and imidosiloxane block copolymer (PSI) containing blocks of PEI units and blocks of dimethylsiloxane units. It is shown that in the PSI film, compared with PEI, the anisotropy, long-range order, and the correlation length of density fluctuations increase. The PSI sample has an asymmetrical biaxial surface texture, unlike PEI, which is characterized by an axial texture. In the direction of the axes of the PSI texture on a micron scale, periodic density oscillations are observed. The results obtained indicate microphase separation in the PSI film due to spatially oriented contact interactions between the blocks of dimethylsiloxane units.

Imaging of Nanoscale Gold in “Intact” Biological Cells by Environmental Electron Microscopy

2021 ◽  
Author(s):  
Domagoj Belić ◽  
Oihane Fragueiro ◽  
Dina Salah ◽  
Alison Beckett ◽  
Martin Volk ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Biological Cells

Immuno-Fluorescence Scanning Electron Microscopy of Biological Cells

2010 ◽  
Vol 18 (5) ◽  
pp. 8-13 ◽  
Author(s):  
Phyllis J. Fisher ◽  
William S. Wessels ◽  
Allan B. Dietz ◽  
Franklyn G. Prendergast
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Function ◽  
Three Dimensional ◽  
Biological Cells ◽  
Cell Surfaces ◽  
Interaction Range ◽  
Spatial Control ◽  
Scanning Electron ◽  
Surface Changes

Scanning electron microscopy (SEM) can produce striking three-dimensional images of biological cells and tissues with submicron resolution of surface morphology. Such cell surfaces are often complex blends of folds, extrusions, and pockets that may be necessary in the positioning of specific molecules within interaction range of each other. Thus, surface changes can have a spatial control over some molecular functions, and identification of select molecules at distinct morphological locations becomes critical to our understanding of total cell function.

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