Showing papers on "Resolution (electron density) published in 1970"
Journal Article•
644 citations
TL;DR: The procedures used in the collection and analysis of x-ray diffraction data from single crystals of ribonuclease-S are described and a preliminary list of the coordinates of all nonhydrogen atoms in this enzyme has been prepared.
465 citations
TL;DR: The deoxyhaemoglobin of horse forms orthorhombic crystals with the space group C2221 and four molecules in the unit cell, which lie on two-fold symmetry axes as mentioned in this paper.
Abstract: THE deoxyhaemoglobin of horse forms orthorhombic crystals with the space group C2221 and four molecules in the unit cell, which lie on two-fold symmetry axes A Fourier synthesis at 55 A resolution showed the tertiary structures of the individual subunits to be closely similar to that of oxyhaemoglobin, but the quaternary structure of the tetramer to be markedly different1,2
257 citations
TL;DR: In this article, the absorption spectrum of the Mg2 molecule, which occurs in a furnace containing Mg vapor, has been photographed with a high resolution spectrograph, and the rotational structures of the bands have been analyzed.
Abstract: The absorption spectrum of the Mg2 molecule, which occurs in a furnace containing Mg vapor, has been photographed with a high resolution spectrograph. The rotational structures of the bands have be...
155 citations
TL;DR: The electron density map shows that the rubredoxin molecule consists of an irregularly folded polypeptide chain which contains an appreciable amount of anti-parallel pleated sheet structure but no alpha helix.
140 citations
TL;DR: In this article, the fourth derivative spectra of chloroplast at − 196°C, obtained by four sequential differentiations of the absorption spectrum, were examined to determine the conditions for optimal signal-to-noise ratio and resolution.
Abstract: — –Fourth derivative spectra of chloroplast at – 196°C, obtained by four sequential differentiations of the absorption spectrum, were examined to determine the conditions for optimal signal-to-noise ratio and resolution. An appreciable improvement in the signal-to-noise ratio was found when the four differentiating intervals were nearly but not exactly equal. The process of differentiating digitized data with the computer was explored in order to define the rules for optimization of the fourth derivative curves.
137 citations
TL;DR: In this paper, electron density maps of human deoxyhaemoglobin at a resolution of 3.5 A reveal new conformations of the C-terminal residues of the β chain and confirm their contribution to the alkaline Bohr effect.
Abstract: Electron density maps of human deoxyhaemoglobin at a resolution of 3.5 A reveal new conformations of the C-terminal residues of the β chain and confirm their contribution to the alkaline Bohr effect. A preliminary comparison of this structure with that of horse oxyhaemoglobin shows that the main differences occur at the chain termini and at certain side chains in the α1β2 interface.
118 citations
118 citations
TL;DR: In this article, it was shown that redundancies in structures can be used in the analysis of aperiodic structures. But the theory is developed in the language of the crystallographer, mainly using the concept of modifying functions.
Abstract: An electron microscope equipped with conventional electron optics can be used as a `diffractometer' for structure research on individual aperiodic objects. The resolution limit of the electron microscope is not the resolution limit of the `diffractometer' and electron structure research with atomic resolution is possible. The advantage is that a diffractometer of this type can measure amplitudes and phases. The theory is developed in the language of the crystallographer, mainly using the concept of modifying functions. It is shown that, as in crystallography, redundancies in structures can be used in the analysis.
74 citations
DOI•
01 Nov 1970TL;DR: In this article, the Fourier transform of the image of a catalase molecule has been investigated and the transfer function of the microscope has been determined by finding the relative contributions from phase and amplitude contrast, which can be extended to high resolution in order to compensate for spherical aberration and defocussing.
Abstract: The effects of defocussing and spherical aberration in the electron microscope image are most simply and directly displayed in the Fourier transform of the image We have investigated the process of image formation by determining the changes in the transform of the image of thin crystals of catalase, which has discrete diffraction maxima in the resolution range of 100 A to 20 A, as a function of defocussing The experimentally measured changes in amplitude and phase of these diffraction maxima have been measured and compared with the predictions of a first order theory of image formation The theory is generally confirmed, and the transfer function of the microscope is completely determined by finding the relative contributions from phase and amplitude contrast A “true” maximum contrast image of the catalase molecule, compensated for the effects of defocussing, is reconstructed from the set of micrographs in the focal series The relation of this compensated image to individual underfocussed micrographs, and the use of underfocus contrast enhancement in conventional electron microscopy, is discussed
This approach and the experimental methods can be extended to high resolution in order to compensate for spherical aberration as well as defocussing, thereby offering the potential for extending the resolution of the microscope well beyond the presently attainable 5 A
58 citations
TL;DR: Extended studies to whole tRNA molecules are able to characterize five steps in the melting process of tRNAPhe (yeast), and the coupling relations between these five transitions will be reported.
TL;DR: The three dimensional structure of adenosine triphosphate in the hydrated disodium salt is reported to a resolution of 0.9 Å.
Abstract: The three dimensional structure of adenosine triphosphate in the hydrated disodium salt is reported to a resolution of 0.9 A.
TL;DR: In this article, a new type of retarding potential difference electron spectrometer using spherical grids is described, and the unique feature of the analyzer is a post monochromator section which selectively collects electrons passing the retarding grids with minimum kinetic energy.
Abstract: A new type of retarding potential difference electron spectrometer using spherical grids is described. The unique feature of the analyzer is a post monochromator section which selectively collects electrons passing the retarding grids with minimum kinetic energy. Factors affecting the resolution of the analyzer are discussed and a comparison with several other spectrometers operating in the resolution range of 0.05% is presented. An application to x‐ray photoelectron spectroscopy is presented.
TL;DR: In this paper, it was shown that in some solid polymers, and in liquids sorbed on, or dispersed in solid lattices, resolution equal to that of pure liquids is obtained.
TL;DR: The following hypothesis is proposed to explain this high resolution of electron microscope autoradiography although the introduction of extremely fine grain development is also considered one of the factors.
Abstract: 1. A method of electron microscope autoradiography was established using nuclear research emulsions manufactured in japan: Sakura NR-H1 and NR-H2. Several biological applications were performed, and simultaneously the improvement in resolution was studied.2. The aim of electron microscope autoradiography is to reveal the exact localization of certain substances at the macromolecular level. In order to attain this object the establishment of an extremely fine grain development method is indispensable.3. Although the limit of resolution in electron microscope autoradiography is supposed to be the diameter of silver halide grains in emulsion, it may be improved by considering the fact that the contact area between the silver grain and the section surface is the minimum unit of resolution.4. Thiamine, labelled with 3H, was made insoluble and precipitated with chloroplatinic acid at fixation. Developed silver grains completely overlap the B1-PtCl6 precipitates.5. The minimum resolution of the electron microscope authoradiogrphy was determined histologically to be within 100A. The following hypothesis is proposed to explain this high resolution although the introduction of extremely fine grain development is also considered one of the factors.Some of latent images are formed at the contact point (surface) between the polyhedral silver halide grain and the section surface. The latent image seems to be formed by the impact of β-particles from directly below, and since it is in contact with the section it remains in place even after development and gelatin removal. This latent image finally becomes a developed silver grain in the electron microscope autoradiogram.
TL;DR: Holograms have been recorded on the surface of Si by means of a photoanodic reaction and resolution better than 2500 lines/mm have been achieved in holographically recorded gratings as discussed by the authors.
Abstract: Holograms have been recorded on the surface of Si by means of a photoanodic reaction. Resolution better than 2500 lines/mm have been achieved in holographically recorded gratings. Diffuse object holograms with reconstruction efficiencies as high as 10% have also been obtained.
TL;DR: In this paper, the results of experiments that were performed to investigate the resolution capabilities of a Bragg imaging system using a cylindrically convergent light beam were presented and compared with theoretical predictions.
Abstract: This paper presents the results of experiments that were performed to investigate the resolution capabilities of a Bragg imaging system using a cylindrically convergent light beam. The usual images formed with such a system show up as silhouetts of the objects being imaged. These silhouettes are superimposed on a light background, which constitutes the visual representation of the incident sound field. The Rayleigh criterion governs the resolution for thin cylindrical objects oriented parallel to the direction of the convergence line of the light beam. For orientation at right angles to this direction, the resolution is of quite a different character. The experimental resolution capabilities for both directions are presented in this paper and are compared with theoretical predictions. Resolution data is also presented for the case of dark‐field imaging, i.e., where the objects appear as bright images on a dark background. In addition, experiments were performed to determine the loss of resolution resulting from the introduction of optically opaque plates between the scattering object and the light‐sound interaction region.
TL;DR: In this paper, the infrared spectra of the v 1 band of AsF 3 and the v 2 bands of PF 3 have been measured with a resolution of 0.03-0.07 cm −1.
TL;DR: Gamma radiations from 84mRb and 86mRr, produced by (n, 2n) reaction on85Rb, and 87Rb respectively, have been studied using a high-resolution Ge(Li) spectrometer as discussed by the authors.
Abstract: Gamma radiations from84m
Rb and86m
Rb, produced by (n, 2n) reaction on85Rb and87Rb respectively, have been studied using a high resolution Ge(Li) spectrometer. Gamma rays of 216.3±0.25, 248.2±0.25 and 464.5±0.25 keV have been found decaying with 20 min half-life and are assigned to84m
Rb. A single gamma ray of 556.1±0.25 keV was found to decay with 62 sec half-life and has been assigned to86m
Rb. The results are incorporated into decay schemes for the two isomers.
TL;DR: In this article, a method for enhancing the resolution of NMR spectra of molecules in solids has been developed and applied to the spectrum of a methyl group and the theoretical aspects are briefly discussed.
TL;DR: A method is discussed for locating the stopping position of pi - mesons in tissue by detecting their position with a plastic scintillator and a magnetostrictive wire spark chamber.
Abstract: A method is discussed for locating the stopping position of pi - mesons in tissue. The gamma -rays emitted following the capture process are collimated and converted to electrons. They are detected with a plastic scintillator and their position is determined with a magnetostrictive wire spark chamber. The sensitivity and resolution of the system are measured.