Showing papers on "Resolution (electron density) published in 1980"
284 citations
TL;DR: It is proposed that the (H3)2 (H4)2 tetramer forms a dislocated disk which defines the central turn of DNA, while the two H2A–H2B dimers lie one on each face, each associated with about one half a turn.
Abstract: Image reconstruction to 22 A resolution of the histone octamer (H3)2(H4)2(H2A)2(H2B)2 shows it to have a 2-fold axis of symmetry, and the overall shape of the left-handed helical spool on which to wind about two turns of a flat superhelix of DNA in the nucleosome. From this structure and the results of various cross-linking studies, we have deduced the arrangement of the individual histones. We propose that the (H3)2(H4)2 tetramer forms a dislocated disk which defines the central turn of DNA, while the two H2A-H2B dimers lie one on each face, each associated with about one half a turn.
279 citations
TL;DR: In this article, the cross-section scattering and distance distribution functions are computed from unsmoothed, smeared scattering data by the indirect transformation method and the influence of finite size, termination effect and the limits of resolution are discussed using results from simulated experiments.
Abstract: The cross-section scattering function and the cross-section distance distribution function are of special interest when lamellar or cylindrical particles are investigated by small-angle scattering techniques with high resolution. These functions can be computed from the unsmoothed, smeared scattering data by the indirect transformation method. This method requires an estimate for the maximum cross-section dimension, which can be found from the distance distribution function of the particle. The influence of finite size, the termination effect and the limits of resolution are discussed using results from simulated experiments.
220 citations
TL;DR: The application of an imaging prism—mirror—prism electron energy filter to high-spatial-resolution and high-energy-resolution microanalysis is examined for specimens of unstained chromatin, films of hematin, sections of osteoblasts, atrial muscle, myelin sheaths, and murine leukemia viruses.
216 citations
200 citations
TL;DR: In this article, the photoacoustic phase signal provided true thermal-wave imaging even in the presence of surface features with strong optical contrast, using piezoelectric detection and a modulation frequency of 185 kHz.
Abstract: Experiments on photoacoustic thermal‐wave microscopy are presented, for the first time, at high resolution. Using piezoelectric detection and a modulation frequency of 185 kHz, we obtain a thermal‐wave resolution of ∼7 μm. We show that the photoacoustic phase signal provides true thermal‐wave imaging even in the presence of surface features with strong optical contrast.
179 citations
TL;DR: In this paper, a resolution of synthetic A-type zeolite suggest possible mechanisms of vitrification and introduction of dislocations into zeolitic structures, and techniques may be developed to extend the lifetime of these, and possibly other beam-sensitive cage or tunnel structures.
Abstract: Interpretable images at 3–5 A resolution of synthetic A-type zeolite suggest possible mechanisms of vitrification and introduction of dislocations into zeolitic structures. Techniques may be developed to extend the lifetime of these, and possibly other, beam-sensitive cage or tunnel structures. Evidence also exists for Si4+ /Al3+ ordering in the aluminosilicate framework.
128 citations
TL;DR: In this paper, high-resolution thermal wave microscopy of surface and subsurface features of an opaque solid using, for the first time, electron beams to generate the signal was performed.
Abstract: We have performed high‐resolution thermal‐wave microscopy of surface and subsurface features of an opaque solid using, for the first time, electron beams to generate the signal.
112 citations
TL;DR: In this paper, the Weinberg-Salam model has been extended to include soft photon effects, with no restriction on the relative magnitudes of the energy resolution Δω and the Z 0 width Γ.
93 citations
TL;DR: The properties of zone plates are outlined, along with the microscope systems that employ them, and a number of applications of x-ray microscopes are surveyed, including in biology, environmental science, and materials science.
Abstract: The scope of this article is to describe a transmission X-ray microscope, possible biological applications of soft X-ray microscopy and preliminary results.For soft X-ray microscopy of biological specimens the wavelength range of 1–10 nm is best suited. Microscopy in this wavelength range requires intense X-ray sources as well as high-resolution X-ray lenses. Intense X-radiation is provided by the synchrotron radiation of electron and positron storage rings. Suited X-ray lenses are zone plates.A theoretical treatment of the contrast mechanism and the radiation damage as well as first experiments yield the following results. Firstly, relatively thick (1–10 μm) biological specimens can be investigated. This means that unsectioned dried and even wet cells and cell organelles in a natural state can be examined. Second, it will be possible to resolve cellular aggregates in live cells with a resolution in the region of ≤10nm.
TL;DR: In this article, a new technique as well as a practical device, Minimum Dose System (MDS), have been developed for taking a high resolution image of radiation-sensitive specimens, on the basis of the principle of minimum beam method.
TL;DR: In this article, high resolution (A ) ion probes are shown to be feasible using either hydrogen ions from field ionization or heavy ions from an electro-hydrodynamic ion source.
IBM1
TL;DR: In this article, degenerate four-wave mixing is used to produce images with a resolution better than 500 lines/mm with 514.5-nm light, which is the state-of-the-art.
Abstract: Conjugate-wave-front generation by degenerate four-wave mixing is used to produce images with a resolution better than 500 lines/mm with 514.5-nm light.
TL;DR: Significant statistical relationships have been found between the parameters characterizing the results and circumstances of the resolutions of seventeen phenylglycine derivatives as mentioned in this paper, and successful predictions given for the results of six independent resolutions prove the utility of these relationships.
TL;DR: A projection, at 15- to 20-A resolution, is presented of the structure of the membrane-bound acetylcholine receptor protein from Torpedo marmorata, which is distinctly asymmetric, with individual morphological subunits barely resolvable.
Abstract: A projection, at 15- to 20-A resolution, is presented of the structure of the membrane-bound acetylcholine receptor protein from Torpedo marmorata. The projection has its axis perpendicular to the membrane plane; its main contribution originates from a hydrated portion of the protein, which extends from the membrane into the aqueous medium. The structure is distinctly asymmetric, with individual morphological subunits barely resolvable. These results have been obtained by noncrystallographic averaging, using correlation functions, applied to electron micrographs of receptor-rich membrane fragments. The micrographs had been taken with minimal beam exposure in a scanning transmission electron microscope.
TL;DR: In this paper, the authors proposed an alternative method of restricting the effecfiue sample volume without the need for the equivalent physical confinement; spinning sample tubes are used with the normal dimensions (5 m m o.d.).
TL;DR: In this paper, the authors describe the structure images of a metal complex of 7 7′, 8, 8′-tetra-cyanoquinodimethane (TCNQ) with the resolution of an atomic level obtained by developing an automated device which is basically similar to that by Unwin and Henderson.
Abstract: High resolution electron microscopy (HREM) has been used for the direct imaging of complex crystal structures. High resolution at an atomic level cannot be expected from most organic crystals due to their high sensitivity to electron radiation damage, although we 1 have previously considered the conspicuous images of chlorine and copper atoms in chlorinated copper phthalocyanine molecules as a special case dependent on the very radiation-resistant property of the compound. In practice, however, some organic crystals may be able to withstand the dosage necessary for the image recording itself but could not tolerate the extra dosage necessary for searching the proper image field and for successive careful focusing. In this respect, the principle of the minimum exposure proposed by Williams and Fisher2 is attractive as it might reduce the unnecessary damage which takes place before the actual image recording. We describe here the structure images of a metal complex of 7 7′, 8, 8′–tetra-cyanoquinodimethane (TCNQ) with the resolution of an atomic level obtained by developing an automated device which is basically similar to that by Unwin and Henderson3. The electron microscope equipped with the low dosage device was JEM-200CX, which gives the instrumental resolution of 0.24 nm.
TL;DR: The reliability index proposed by Zanazzi and Jona for low-energy electron diffraction (LEED) crystallography has been investigated by assessing its ability to compare experimental intensity versus energy curves with those calculated for different non-structural parameters as discussed by the authors.
Abstract: A reliability index () proposed for low-energy electron diffraction (LEED) crystallography by Zanazzi and Jona has been investigated by assessing its ability to compare experimental intensity versus energy curves with those calculated for different non-structural parameters. Included in the latter are the energy dependence of the real part of the inner potential for Cu(111), and the individual variations of the imaginary potential and the surface Debye temperature for Rh(111). Also an error has been corrected in one atomic potential used in our earlier work on Rh(100) and Rh(111), and this allows a resolution of the discrepancy found previously in the geometrical structures indicated by a band structure potential and a superposition potential for rhodium. The results here provide general support for the use of the index in conjunction with procedures frequently followed in LEED crystallography.
TL;DR: In this paper, a γ-ray imaging detector, working at ambient temperature, with good energy resolution, good spatial accuracy and reasonable detection efficiency has been built, and the criteria for evaluation of light yield and energy resolution are given.
TL;DR: In this article, two ion guns are used to develop the profile, each symmetrically inclined to the surface normal, whose effect is to suppress the formation of ion induced topography.
TL;DR: The crystal structure of Taka-amylase A was studied by an X-ray diffraction method at 3 A resolution and showed that a maltose unit was bound in the active center left.
Abstract: The crystal structure of Taka-amylase A was studied by an X-ray diffraction method at 3 A resolution. A total of 452 amino acid residues were found from the electron density map at the present stage. The four disulfide bonds and the branched carbohydrate were also located on the map. The difference electron density map of the maltotriose-soaked crystal showed that a maltose unit was bound in the active center left. The binding of iodine atoms to the enzyme was also studied.
TL;DR: Two low resolution structures are compared with regard to differences in quaternary structure on two phycobiliproteins: C- Phycocyanin from Anabaena variabilis and B-Phycoerythrin from Porphyridium cruentum.
TL;DR: In this paper, the vibration-rotation emission spectrum of the nitric oxide molecule has been recorded with a high-resolution Fourier transform interferometer (resolution 10 −2 cm −1 ) in the spectral range 2900 − 3810 cm − 1.
TL;DR: Determination of the density of glutaraldehyde-fixed, water-equilibrated crystals indicates that there is one subunit per asymmetric unit, and three-dimensional packing of the cytochrome oxidase dimer in the unit cell has been deduced from computer reconstructed images of the three principal projections along the crystallographic axes.
TL;DR: The structure of D-galactose-binding protein, a receptor for both high affinity active transport system and chemotaxis in Escherichia coli, has been solved at 4.1 A resolution using three heavy atom derivatives.