scholarly journals Introductory Chapter: Electron Crystallography

2020 ◽  
Author(s):  
Devinder Singh
Keyword(s):  
Electron Crystallography

A Novel Reconstitution Method for Inducing the Formation of Regular 2-Dimensional Arrays of Membrane Proteins and Lipids

1988 ◽  
Vol 46 ◽  
pp. 152-153 ◽  
Author(s):  
A. Engel ◽  
A. Holzenburg ◽  
K. Stauffer ◽  
J. Rosenbusch ◽  
U. Aebi
Keyword(s):  
Membrane Proteins ◽  
Flow Rate ◽  
Lipid Membranes ◽  
Functional Characterization ◽  
Dimensional Structure ◽  
Electron Crystallography ◽  
Peltier Element ◽  
Protein Ratio ◽  
Precise Control ◽  
3 Dimensional

Reconstitution of solubilized and purified membrane proteins in the presence of phospholipids into vesicles allows their functions to be studied by simple bulk measurements (e.g. diffusion of differently sized solutes) or by conductance measurements after transformation into planar membranes. On the other hand, reconstitution into regular protein-lipid arrays, usually forming at a specific lipid-to-protein ratio, provides the basis for determining the 3-dimensional structure of membrane proteins employing the tools of electron crystallography.To refine reconstitution conditions for reproducibly inducing formation of large and highly ordered protein-lipid membranes that are suitable for both electron crystallography and patch clamping experiments aimed at their functional characterization, we built a flow-dialysis device that allows precise control of temperature and flow-rate (Fig. 1). The flow rate is generated by a peristaltic pump and can be adjusted from 1 to 500 ml/h. The dialysis buffer is brought to a preselected temperature during its travel through a meandering path before it enters the dialysis reservoir. A Z-80 based computer controls a Peltier element allowing the temperature profile to be programmed as function of time.

Enhanced information from biological materials through technological improvements in cryo-electron microscopy

1992 ◽  
Vol 50 (1) ◽  
pp. 788-789
Author(s):  
Marc J.C. de Jong ◽  
Wim M. Busing ◽  
Max T. Otten
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Biological Materials ◽  
Electron Crystallography ◽  
Cryo Electron Microscopy ◽  
Transmission Electron ◽  
The Many ◽  
Technological Improvements ◽  
Beam Damage

Biological materials damage rapidly in the electron beam, limiting the amount of information that can be obtained in the transmission electron microscope. The discovery that observation at cryo temperatures strongly reduces beam damage (in addition to making it unnecessaiy to use chemical fixatives, dehydration agents and stains, which introduce artefacts) has given an important step forward to preserving the ‘live’ situation and makes it possible to study the relation between function, chemical composition and morphology.Among the many cryo-applications, the most challenging is perhaps the determination of the atomic structure. Henderson and co-workers were able to determine the structure of the purple membrane by electron crystallography, providing an understanding of the membrane's working as a proton pump. As far as understood at present, the main stumbling block in achieving high resolution appears to be a random movement of atoms or molecules in the specimen within a fraction of a second after exposure to the electron beam, which destroys the highest-resolution detail sought.

Direct phase determination in electron crystallography: small organic molecules

1992 ◽  
Vol 50 (2) ◽  
pp. 1166-1167
Author(s):  
Douglas L. Dorset
Keyword(s):  
Organic Molecules ◽  
Data Sets ◽  
Temperature Structure ◽  
3D Analysis ◽  
Intensity Data ◽  
Electron Crystallography ◽  
Phase Determination ◽  
Measured Intensity ◽  
3D Data

The quantitative use of electron diffraction intensity data for the determination of crystal structures represents the pioneering achievement in the electron crystallography of organic molecules, an effort largely begun by B. K. Vainshtein and his co-workers. However, despite numerous representative structure analyses yielding results consistent with X-ray determination, this entire effort was viewed with considerable mistrust by many crystallographers. This was no doubt due to the rather high crystallographic R-factors reported for some structures and, more importantly, the failure to convince many skeptics that the measured intensity data were adequate for ab initio structure determinations.We have recently demonstrated the utility of these data sets for structure analyses by direct phase determination based on the probabilistic estimate of three- and four-phase structure invariant sums. Examples include the structure of diketopiperazine using Vainshtein's 3D data, a similar 3D analysis of the room temperature structure of thiourea, and a zonal determination of the urea structure, the latter also based on data collected by the Moscow group.

Defocus ramp correction in spot-scan imaging

1992 ◽  
Vol 50 (1) ◽  
pp. 130-131
Author(s):  
Kenneth H. Downing
Keyword(s):  
Computer Control ◽  
Three Dimensional ◽  
Sufficient Accuracy ◽  
Objective Lens ◽  
Electron Crystallography ◽  
Contrast Transfer Function ◽  
Tilt Axis ◽  
Specimen Height ◽  
The Difference ◽  
Envelope Functions

Three-dimensional structures of a number of samples have been determined by electron crystallography. The procedures used in this work include recording images of fairly large areas of a specimen at high tilt angles. There is then a large defocus ramp across the image, and parts of the image are far out of focus. In the regions where the defocus is large, the contrast transfer function (CTF) varies rapidly across the image, especially at high resolution. Not only is the CTF then difficult to determine with sufficient accuracy to correct properly, but the image contrast is reduced by envelope functions which tend toward a low value at high defocus.We have combined computer control of the electron microscope with spot-scan imaging in order to eliminate most of the defocus ramp and its effects in the images of tilted specimens. In recording the spot-scan image, the beam is scanned along rows that are parallel to the tilt axis, so that along each row of spots the focus is constant. Between scan rows, the objective lens current is changed to correct for the difference in specimen height from one scan to the next.

Factors in Photographic Emulsions for Low Dose Electron Crystallography

1980 ◽  
Vol 38 ◽  
pp. 230-231
Author(s):  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
Radiation Damage ◽  
Low Dose ◽  
Damage Effect ◽  
Photographic Emulsion ◽  
Electron Crystallography ◽  
Electron Microscopic ◽  
X Ray ◽  
Signal Contrast ◽  
Diffraction Patterns ◽  
Photographic Emulsions

With the advances in preparing biological materials in a thin and highly ordered form, and in maintaining them hydrated under vacuum, electron crystallography has become an important tool for biological structure investigation at high resolution (1,2). However, the electron radiation damage would limit the capability of recording reflections with low intensities in an electron diffraction pattern. It has been demonstrated that the use of a low temperature stage can reduce the radiation damage effect and that one can expose the specimen with a higher dose in order to increase the signal contrast (3). A further improvement can be made by selecting a proper photographic emulsion. The primary factors in evaluating the suitability of photographic emulsion for recording low dose diffraction patterns are speed, fog level, electron response at low electron exposure, linearity, and usable range of exposure. We have compared these factors with three photographic emulsions including Kodak electron microscopic plate (EMP), Industrex AA x-ray film (AA x-ray) and Kodak nuclear track film (NTB3).

Introduction: Plato’s Nightmare

2018 ◽  
Author(s):  
John Marmysz
Keyword(s):  
Immanuel Kant ◽  
Martin Heidegger ◽  
Friedrich Nietzsche ◽  
Objective Reality

This introductory chapter examines the “problem” of nihilism, beginning with its philosophical origins in the ideas of Plato, Immanuel Kant, Friedrich Nietzsche and Martin Heidegger. It is argued that film is an inherently nihilistic medium involving the evocation of illusory worlds cut loose from objective reality. This nihilism of film is distinguished from nihilism in film; the nihilistic content also present in some (but not all) movies. Criticisms of media nihilism by authors such as Thomas Hibbs and Darren Ambrose are examined. It is then argued, contrary to such critics, that cinematic nihilism is not necessarily degrading or destructive. Because the nihilism of film encourages audiences to linger in the presence of nihilism in film, cinematic nihilism potentially trains audiences to learn the positive lessons of nihilism while remaining safely detached from the sorts of dangers depicted on screen.

Introduction: Exploring Russian nationalisms

2018 ◽  
Author(s):  
Pål Kolstø ◽  
Helge Blakkisrud
Keyword(s):  
The State ◽  
Complex Interplay ◽  
Recent Developments ◽  
Part Structure

Russian societal nationalism comes in various guises, both ethnic and imperialist. Also Putin’s rhetoric is marked by the tensions between ethnic and state-focused, imperialist thinking. Noting the complex interplay of state nationalism and societal nationalism, this introductory chapter examines the mental framework within which Russian politicians were acting prior to the decision to annex Crimea. The chapter develops a typology of Russian nationalisms, surveys recent developments, and presents the three-part structure of this book: official nationalism, radical and other societal nationalisms, and identities/otherings. It concludes that after the annexation of Crimea, when the state took over the agenda of both ethnic and imperialist nationalists in Russia, societal nationalism finds itself at low ebb.

Introduction

2017 ◽  
Author(s):  
Nancy Woloch
Keyword(s):  
Labor Market ◽  
Women Reformers ◽  
Single Sex ◽  
Feminist Organization ◽  
And Shifts ◽  
Women's Bureau

This introductory chapter provides an overview of single-sex protective laws. The longevity of protective laws rests in part on reformers' bifocal defense. The goal of such laws, their proponents claimed, was to compensate for women's disadvantages in the labor market and to serve as the linchpin of a larger plan to achieve wage-and-hour standards for all employees. This double-planked rationale—though contradictory—proved versatile and enduring; it suited constituents with varied priorities. Protective laws' longevity also rested on effective social feminist organization and, after 1920, on the federal Women's Bureau. In retrospect, single-sex protective laws were an unwieldy means to achieve egalitarian ends—or what women reformers of the 1920s called “industrial equality.” However, critics charged that the laws failed to redress disadvantage and even compounded it. Protection's supporters also confronted developments they could not anticipate and shifts in attitude they could not foresee.

Bringing Moral Culture into the Fray

2017 ◽  
Author(s):  
Justin Farrell
Keyword(s):  
Environmental Conflict ◽  
Scientific Study ◽  
Theoretical Argument ◽  
Moral Culture ◽  
Social Scientific Study ◽  
The Social ◽  
Social Scientific ◽  
Basic Level

This introductory chapter briefly presents the conflict in Yellowstone, elaborates on the book's theoretical argument, and specifies its substantive and theoretical contributions to the social scientific study of environment, culture, religion, and morality. The chapter argues that the environmental conflict in Yellowstone is not—as it would appear on the surface—ultimately all about scientific, economic, legal, or other technical evidence and arguments, but an underlying struggle over deeply held “faith” commitments, feelings, and desires that define what people find sacred, good, and meaningful in life at a most basic level. An overview of the subsequent chapters is also presented.

A Passion for Politics

2018 ◽  
Author(s):  
Biancamaria Fontana
Keyword(s):  
Political Life ◽  
Literary Works

This introductory chapter provides an account of Germaine de Staël's approach to politics that brings out the independence and originality of her contribution. Its main focus is the evolution of her views in the years 1789 to 1800, when she had the opportunity to take part (albeit intermittently) in French political life, and to set forth projects and strategies connected with it. The chapter touches only on Staël's best-known—and more widely studied—fictional and literary works, though naturally these do also have some political relevance. It has been suggested that the protracted exile into which she was forced during the empire was at the origin of Staël's major literary achievements, as it provided her with both the opportunity and the incentive to develop her true potential as a writer.

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