Showing papers on "Resolution (electron density) published in 1989"
TL;DR: This study demonstrates the effectiveness of multiwavelength anomalous diffraction procedures for macromolecular crystallography and provides a basis for detailed study of biotin-avidin interactions.
Abstract: A three-dimensional crystal structure of the biotin-binding core of streptavidin has been determined at 3.1-A resolution. The structure was analyzed from diffraction data measured at three wavelengths from a single crystal of the selenobiotinyl complex with streptavidin. Streptavidin is a tetramer with subunits arrayed in D2 symmetry. Each protomer is an 8-stranded beta-barrel with simple up-down topology. Biotin molecules are bound at one end of each barrel. This study demonstrates the effectiveness of multiwavelength anomalous diffraction (MAD) procedures for macromolecular crystallography and provides a basis for detailed study of biotin-avidin interactions.
566 citations
TL;DR: In this paper, the authors propose that having more aspects to know and understand will lead to becoming a more precious person, and becoming more precious can be situated with the presentation of how your knowledge much.
Abstract: Of course, from childhood to forever, we are always thought to love reading. It is not only reading the lesson book but also reading everything good is the choice of getting new inspirations. Religion, sciences, politics, social, literature, and fictions will enrich you for not only one aspect. Having more aspects to know and understand will lead you become someone more precious. Yea, becoming precious can be situated with the presentation of how your knowledge much.
532 citations
318 citations
TL;DR: Gauthier-Villars as discussed by the authors implique l'accord avec les conditions générales d'utilisation (http://www.numdam.org/conditions).
Abstract: © Gauthier-Villars (Éditions scientifiques et médicales Elsevier), 1989, tous droits réservés. L’accès aux archives de la revue « Annales scientifiques de l’É.N.S. » (http://www. elsevier.com/locate/ansens) implique l’accord avec les conditions générales d’utilisation (http://www.numdam.org/conditions). Toute utilisation commerciale ou impression systématique est constitutive d’une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright.
243 citations
TL;DR: In this article, a distance sensor consisting of a sharply pointed vibrating tip, which is part of a high-Q quartz resonator driven at its resonance frequency, is incorporated into a scanning device.
Abstract: Scanning near-field acoustic microscopy (SNAM) is a new method for imaging the topography of nonconducting surfaces at a potential lateral resolution in the sub-micron range. The basic element of this method is a distance sensor consisting of a sharply pointed vibrating tip, which is part of a high-Q quartz resonator driven at its resonance frequency. The decrease of the resonance frequency or of the amplitude of vibration when an object comes into the proximity of the tip serves as the important signal. The dependence of this signal on pressure and composition of the coupling gas shows that the hydrodynamic forces in the gas are responsible for the coupling between object and tip. The sensor is incorporated into a scanning device. Well-resolved line scans of a grating of 8 μm periodicity, a lateral resolution of 3 μm and a vertical resolution of 5nm have been achieved in our first experiments.
200 citations
TL;DR: By defining a suitable measure for the comparison of images, changes in resolution can be treated with the same tool as changes in color resolution, and the possibility of trading spatial for gray-level resolution and vice versa is explored.
Abstract: It is shown that by defining a suitable measure for the comparison of images, changes in resolution can be treated with the same tool as changes in color resolution. A gray-tone image, for example, can be compared to a half-tone image having only two colors (black and white), but of higher spatial resolution. A graph-theoretical definition of the basic measure used is introduced. This is followed by application to spatial resampling and gray-level requantization. This results in a hybrid treatment of resolution, and the possibility of trading spatial for gray-level resolution and vice versa. >
170 citations
TL;DR: In most surface areas the solution structure appears more disordered than the crystal structure, with the exception of Tyr15, which was not observed in the X-ray diffraction.
146 citations
128 citations
TL;DR: An image processing scheme to determine the relative tilt, translation, and sampling parameters of the different data sets is devised, which involves the use of a modified phase cross-correlation function, which produces a very sharp maximum.
106 citations
IBM1
TL;DR: In this article, the authors used the scanning tunnelling microscope (STM) to measure the temperature rise owing to the absorption of tunable monochromatic light, giving a direct measurement of the absorption spectrum of a sample as a function of illuminating wavelength.
Abstract: SEVERAL variants of the scanning tunnelling microscope (STM) have been developed since its invention1. Here we present the first demonstration of a new type of microscope, based on the STM, that is capable of recording optical absorption spectra with nanometre (that is, molecular) resolution. Our starting point is conventional photothermal spectroscopy, in which the temperature rise owing to the absorption of tunable monochromatic light is measured, giving a direct measurement of the absorption spectrum of a sample as a function of illuminating wavelength. The spatial resolution of such measurements is determined by the sizes of the pump beam or detector, whichever is smaller. We use the STM to measure the 'thermoelectric' tunnelling voltage due to absorption. Conventional photothermal measurements2,3 have been limited to a resolution of ∼1 μm, although we have recently developed a thermal sensor with a spatial resolution of ∼50 nm (ref. 4), and suggested its use for spectroscopy on that scale5. The STM, however, permits resolution of about 1 nm, and as the image is controlled by the thermal properties of the sample, our technique can image variations in the thickness of surface films, and changes in sub-surface characteristics, as well as chemical variations.
TL;DR: In this paper, a low-dose technique on a cryo-electron microscope equipped with a helium-cooled superconducting objective lens was used to reconstruct projected images of the porin trimer to a resolution of up to 3.5 A.
01 Jan 1989
TL;DR: Scanning electron microscopy has become a useful tool for examining the external characteristics related to various developmental processes in plants with greater depth of field and at a higher magnification and resolution than with light microscopy.
Abstract: Scanning electron microscopy (SEM) has become a useful tool for examining the external characteristics related to various developmental processes in plants. With SEM, the external fractures of a tissue can be observed with a greater depth of field and at a higher magnification and resolution than with light microscopy.
01 Jan 1989
TL;DR: In this paper, the projected structures of two unstained periodic biological specimens, the purple membrane and catalase, have been determined by electron microscopy to resolutions of 7 A and 9 A, respectively.
Abstract: The projected structures of two unstained periodic biological specimens, the purple membrane and catalase, have been determined by electron microscopy to resolutions of 7 A and 9 A, respectively. Glucose was used to facilitate their in vacuo preservation and extremely low electron doses were applied to avoid their destruction. The information on which the projections are based was extracted from defocussed bright-field micrographs and electron diffraction patterns. Fourier analysis of the micrograph data provided the phases of the Fourier components of the structures; measurement of the electron diffraction patterns provided the amplitudes. Large regions of the micrographs (3000 to 10,000 unit cells) were required for each analysis because of the inherently low image contrast ( Our methods appear to be limited in resolution only by the performance of the microscope at the unusually low magnifications which were necessary. Resolutions close to 3 A should ultimately be possible.
TL;DR: This work has utilized VLM in conjunction with SEM and HVEM to correlate changes in shape and surface structure with changes in the internal structure of platelets, and found it advantageous to use colloidal gold-labeling procedures, because these markers are detectable by all three forms of microscopy.
Abstract: Scanning electron microscopy (SEM), especially low-voltage (1 KeV) high-resolution SEM, can be used in conjunction with stereo pair high-voltage (1 MeV) transmission electron microscopy (HVEM) of whole spread cells or thick sections effectively to correlate surface structure with internal structure. Surface features such as microvilli, pits, pseudopodia, ruffles, attached virus, and other surface-related morphologic characteristics can be identified using SEM, while underlying cytoskeletal structure and organelle organization can be viewed by HVEM of the same preparation. However, the need to "prepare" cells for electron microscopy precludes observation in the living state. The use of several types of video-enhanced light microscopy (VLM) permits observation of living cells such that certain surface and internal features can be observed at a relatively high level of resolution or detection. Thus, changes in living cells can be followed, and at appropriate times the cells may be chemically fixed or rapidly frozen and prepared for ultrastructural examination by electron microscopy. We have utilized VLM in conjunction with SEM and HVEM to correlate changes in shape and surface structure with changes in the internal structure of platelets. In addition, we have found it advantageous to use colloidal gold-labeling procedures, because these markers are detectable by all three forms of microscopy. Using this approach we have labeled platelet membrane GPIIb/IIIa, a receptor for RGD-containing adhesive proteins, with gold-fibrinogen or gold-anti-IIb/IIIa. The initial binding and subsequent movement of gold-fibrinogen-IIb/IIIa complexes in living platelets was followed by VLM. The movement of individual labels could be mapped. Subsequent observation by low-voltage (1 KeV) high-resolution SEM and HVEM permits visualization of the same individual receptors tracked by LM. The final position on the membrane or the position-in-transit when fixative was added was determined relative to surface ultrastructure (SEM) and internal, particularly cytoskeletal, ultrastructure (HVEM).
TL;DR: In this article, the Fourier transform spectra of ammonia, 14 NH 3, have been measured in the 3-μm region with 0.005-cm −1 resolution, and the ν 1, ν 3, and 2 ν 4 bands have been assigned and partially analyzed.
TL;DR: In this article, it was shown that in the limit of a thin specimen, it is possible to transform all the intensity information available in the microdiffraction plane of a scanning transmission electron microscope (STEM) to obtain the complex specimen function at wavelength-limited resolution.
TL;DR: In this article, the structure of the orthorhombic form of Tl2Ba2CuO6+δ(Tc=90 K), synthesized in sealed gold tubes using BaO2, has been refined using high resolution neutron powder diffraction data collected at 4 K.
Abstract: The structure of the orthorhombic form of Tl2Ba2CuO6+δ(Tc=90 K), synthesized in sealed gold tubes using BaO2, has been refined using high resolution neutron powder diffraction data collected at 4 K. No significant deficiency in metal stoichiometry could be inferred from the crystal structure analysis. The space group (Fmmm) used in this study gives essentially the same results as the alternative (Abma, Amaa) proposed in earlier work. The large amount of disorder that exists in the Tl2O2-slab is mirrored in the large thermal parameters for this structural unit compared to those for the CuO2 sheet. A site at ( built1 4 built1 4 built1 4 ) is occupied by an amount of oxygen to give overall stoichiometry Tl2Ba2CuO6.10, suggesting that oxygen non-stoichiometry plays an important role in producing high Tc superconductivity in this system. Analysis of single crystal X-ray diffraction data of tetragonal Tl2Ba2CuO6+ δ is totally consistent with the neutron powder diffraction results.
TL;DR: An analytical formula useful for the computation of the diffusion affected signal as a function of continuous time for a time variant gradient is derived and evaluated as an integral part of the overall diffusion effects in micron resolution NMR imaging or NMR microscopy.
Abstract: A generalized formulation of the diffusion related nuclear magnetic resonance(NMR) signal is derived from a random walk model. Previous analyses performed in the NMR spectroscopy were the formulations of the diffusion related signal amplitude at a specific time, such as the spin echo formation time. They are, in general, not applicable to continuous time domain analyses. In this paper, we have extended the theory to the two‐dimensional imaging case and derived an analytical formula useful for the computation of the diffusion affected signal as a function of continuous time for a time variant gradient. This formulation will be useful in NMR imaging, especially in NMR microscopy where the diffusion associated signal attenuation is serious due to the strong gradient fields (100–1000 G/cm), and at the same time data are acquired continuously for the acquisition period. In addition to the loss of the resolution and signal‐to‐noise ratio due to the random phase fluctuation by diffusion, the variation of the intensity during the data acquisition period introduces a line broadening whose full width at half‐maximum is found to be much larger than the bandwidth‐limited resolution or diffusion related intrinsic resolution. This line spreading effect is integrated in a computer simulation and is evaluated as an integral part of the overall diffusion effects in μm resolution NMR imaging or NMR microscopy.
TL;DR: In this paper, the nuclear and electronic contributions to the third-order susceptibility χ3 in a phase conjugation experiment were resolved by a method of resolving the nuclear contributions.
Abstract: We present a method of resolving the nuclear and electronic contributions to the third‐order susceptibility χ3 in a phase conjugation experiment. The technique is applied to octylmethylpolysilane yielding χ3 (electronic)=(1.8±0.5)×10−12 esu and χ3(nuclear)=(1.1±0.4)×10−12 esu at 532 nm.
TL;DR: In this paper, the authors present a formal notation for the Filtered Blowing-Up and the Induced Filtration on Local Cohomology Groups, and the case when G has an isolated singularity.
Abstract: Introduction. §0. Notation and Conventions. Chapter 1. Filtered Rings and Filtered Blowing-Ups. § 1. Filtered Blowing-Up and the Induced Filtration on Local Cohomology Groups. § 2. The Divisor Class Group of Normal Rees Algebras. § 3. The Dualizing Module on the Filtered Blowing-Up and the Criterion for Gorenstein Property. Appendix to § 3. Graded Dualizing Complex for Graded Rings and Duality for Projective Morphisms. § 4. Criterion for Normality and Rational Singularity § 5. The Case When G Has an Isolated Singularity. Chapter 2. Normal Two-Dimensional Singularities with \"Star-Shaped\" Resolution. § 6. \"Star-Shaped\" Resolution and the Filtration. § 7. Gorenstein Singularities with \"Star-Shaped\" Resolution. § 8. The Case with pa = 2. References.
Journal Article•
TL;DR: In this paper, a superimposed electromagnetic triode configuration is introduced, whose resolution approachs the theoretical limits of an uniform accelerating field, and it is suggested that image energy filtering should lead to further improvement.
IBM1
TL;DR: Absolute optical ranging has been demonstrated by wavelength-multiplexed interferometry with a range resolution of 200 nm, well below the single-wavelength ambiguity, providing the means for combining single- and multiple-wa wavelength interferometric measurements to achieve unambiguous distance measurement with nanometer resolution.
Abstract: Absolute optical ranging has been demonstrated by wavelength-multiplexed interferometry with a range resolution of 200 nm, well below the single-wavelength ambiguity. Two current- and temperature-tunable GaAlAs laser diodes (850 nm) provide an equivalent wavelength below 100 μm and a resolution of less than 200 nm. The achievement of such resolution provides the means for combining single- and multiple-wavelength interferometric measurements to achieve unambiguous distance measurement with nanometer resolution. The ranging system is also used to profile unambiguously an integrated circuit structure with a 2.5-μm surface topography.
Journal Article•
TL;DR: An outline of the ultra‐high resolution SEM, techniques for specimen preparation, findings of some biological materials by these techniques, and guidelines to making the specimens are described.
TL;DR: In this paper, an outline of the ultra-high resolution scanning electron microscope (SEM), techniques for specimen preparation, findings of some biological materials by these techniques, and guidelines to making the specimens, are described.
01 Feb 1989-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, a detailed study has been made of the use of MeV heavy ions (2 ≤, Z1 ≤, 10) to improve the limits of depth resolution in surface analysis.
Abstract: A detailed study has been made of the use of MeV heavy ions (2 ≤, Z1 ≤, 10) to improve the limits of depth resolution in surface analysis. While there have been detailed studies of the optimization of the use of He projectiles at glancing angles, heavier ions have received limited attention principally because the energy resolution of surface barrier detectors is significantly degraded for heavy ions and this is a major contributor to limiting the depth resolution of a system near the surface. In this paper the surface barrier detector will be compared with the electrostatic energy analyser (EEA) which does not suffer the same limitations in energy resolution (and hence depth resolution). This work extends a number of limited experimental studies of the application of heavy ions and electrostatic analysers to enhanced depth resolution, though these have rarely been used together. It will be shown that exceptional improvements in depth resolution can be achieved, and subject to the limitations of the theoretical models used in the computer simulation of heavy ion backscattering, it is predicted that depth resolutions of as small as 0.5 nm may be achievable. An algorithm for ascertaining the optimum depth resolution conditions for heavy projectiles is also derived which will identify the best angle of incidence, depth resolution and projectile for a given sample to an accuracy of better than 10%.
TL;DR: In this paper, the infrared spectrum of CH 3 OH between 950 and HOOcm −1 has been measured by a high resolution Fourier transform spectrometer, and a catalog of 3410 assigned lines is presented, as well as the Taylor development tables for evaluating the energies of the upper levels of the corresponding transitions.
TL;DR: The aspartylprotease of the human immunodeficiency virus HIV-1 (NY5) has been crystallized in a form suitable for x-ray diffraction analysis and the symmetry of this space group could accommodate the proposed active dimer species of the protease if the 2-fold axis were coincident with one of the crystallographic 2- fold axes.