Showing papers on "Resolution (electron density) published in 1994"
TL;DR: It is hoped that site-specific radial distribution functions obtained from high-quality diffraction data will produce a picture of macromolecular solvation consistent with available experimental data and computational results.
341 citations
TL;DR: In this article, a new electron energy analyzer for photoelectron spectroscopy is described, which is a full hemisphere with a mean radius of 200mm and can be operated in different modes, optimizing transmission, spatial resolution or angular resolution.
246 citations
TL;DR: In this article, a model of filamentous bacteriophages has been developed to fit quantitative X-ray fiber diffraction data to 30 A resolution in the meridional direction and 7 A resolution at the equatorial direction.
219 citations
TL;DR: Tapered glass capillaries have successfully condensed hard x-ray beams to ultrasmall dimensions providing unprecedented spatial resolution for the characterization of materials, and a spatial resolution of 50 nanometers was obtained while imaging a lithographically prepared gold pattern with x-rays.
Abstract: Tapered glass capillaries have successfully condensed hard x-ray beams to ultrasmall dimensions providing unprecedented spatial resolution for the characterization of materials. A spatial resolution of 50 nanometers was obtained while imaging a lithographically prepared gold pattern with x-rays in the energy range of 5 to 8 kiloelectron volts. This is the highest resolution scanning x-ray image made to date with hard x-rays. With a beam 360 nanometers in diameter, Laue diffraction was observed from the smallest sample volume ever probed by x-ray diffraction, 5 x 10(-3) cubic micrometers.
191 citations
TL;DR: 3D and nondestructive investigation of structures in mineralized bone on the 2 micron level is feasible and it should be possible to study tomographically the 3D distribution and amount of osteoclastic resorption in the surrounding bone structure.
176 citations
TL;DR: It is demonstrated that the atomic force microscope is capable of imaging the surface of the hexagonally packed intermediate layer of Deinococcus radiodurans in buffer solution with a lateral resolution of 1 nm and a vertical resolution of 0.1 nm.
Abstract: The atomic force microscope has the potential to monitor structural changes of a biological system in its native environment. To correlate them with the biological function at a molecular level, high lateral and vertical resolution are required. Here we demonstrate that the atomic force microscope is capable of imaging the surface of the hexagonally packed intermediate layer of Deinococcus radiodurans in buffer solution with a lateral resolution of 1 nm and a vertical resolution of 0.1 nm. On average, these topographs differ from those determined by electron microscopy by <0.5 nm.
165 citations
TL;DR: It is concluded that the most likely crystal space group is p42(1)2, and none of the patterns showed the precise 422 symmetry expected, almost certainly because the crystals were slightly tilted.
154 citations
TL;DR: Ultrahigh-resolution three-dimensional images of a microscopic test object were made with soft x-rays collected with a scanning transmission x-ray microscope by means of an algorithm using an algebraic reconstruction technique, and some features were clearly reconstructed with a depth resolution of ∼1000 angstroms.
Abstract: Ultrahigh-resolution three-dimensional images of a microscopic test object were made with soft x-rays collected with a scanning transmission x-ray microscope The test object consisted of two different patterns of gold bars on silicon nitride windows that were separated by ∼5 micrometers Depth resolution comparable to the transverse resolution was achieved by recording nine two-dimensional images of the object at angles between –50 and +55 degrees with respect to the beam axis The projections were then combined tomographically to form a three-dimensional image by means of an algorithm using an algebraic reconstruction technique A transverse resolution of ∼1000 angstroms was observed Artifacts in the reconstruction limited the overall depth resolution to ∼6000 angstroms; however, some features were clearly reconstructed with a depth resolution of ∼1000 angstroms
124 citations
TL;DR: In this paper, the authors demonstrate how to obtain the ultimate lateral resolution in surface plasmon microscopy (SPM) (diffraction limited by the objective) by determining the optimal depth values for wavelengths ranging from 531 to 676 nm.
Abstract: In this article we demonstrate how to obtain the ultimate lateral resolution in surface plasmon microscopy (SPM) (diffraction limited by the objective). Surface plasmon decay lengths are determined theoretically and experimentally, for wavelengths ranging from 531 to 676 nm, and are in good agreement. Using these values we can determine for each particular situation which wavelength should be used to obtain an optimal lateral resolution, i.e., where the plasmon decay length does not limit the resolution anymore. However, there is a trade‐off between thickness resolution and lateral resolution in SPM. Because of the non‐optimal thickness resolution, we use several techniques to enhance the image acquisition and processing. Without these techniques the use of short wavelengths results in images where the contrast has vanished almost completely. In an example given, a 2.5 nm SiO2 layer on a gold layer is imaged with a lateral resolution of 2 μm, and local reflectance curves are measured to determine the laye...
124 citations
TL;DR: Using fluorescence excitation spectroscopy single pentacence molecules were studied under a microscope at a temperature of 1.8 K in this article, where the position of the single molecule was characterized by the x-and y-coordinates in the spatial domain and by its absorption frequency in the spectral domain.
103 citations
01 Jan 1994
Patent•
16 Feb 1994TL;DR: In this article, a method and apparatus for automatically switching the resolution of an image stored in a memory when the memory can no longer store another image with the present resolution is presented. But the method is limited to the case where the resolution is above a first predetermined level and below a second predetermined level.
Abstract: A method and apparatus for automatically switching the resolution of an image stored in a memory when the memory can no longer store another image with the present resolution. A processor first determines the amount of available memory in the memory for storing image data. The resolution is then automatically switched from a high resolution to a low resolution when available memory is above a first predetermined level and below a second predetermined level.
TL;DR: In this article, a dynamic 2D IR spectroscopy can provide insights into plymer deformation mechanisms, identify interactions in polymer blends, and enhance the resolution of overlapping spectral features.
Abstract: Dynamic 2d IR spectroscopy can provide insights into plymer deformation mechanisms, identify interactions in polymer blends, and enhance the resolution of overlapping spectral features
TL;DR: In this article, the spectrum of CH 2 D 2 has been recorded with a Fourier transform Bruker IFS HR spectrometer with a resolution of 0.003 cm −1.
TL;DR: The 2-D crystals of CHIP28 display order extending beyond the limit typically achieved by negative staining and therefore may be amenable to high-resolution structure analysis by cryo-electron microscopy.
Abstract: Osmotic water transport across plasma membranes in erythrocytes and several epithelial cell types is facilitated by CHIP28, a water-selective membrane channel protein In order to examine the structure of CHIP28 in membranes, large (15-25-microns diameter), highly ordered, two-dimensional (2-D) crystals of purified and deglycosylated erythrocyte CHIP28 were generated by reconstitution of detergent-solubilized protein into synthetic lipid bilayers via detergent dialysis Fourier transforms computed from low-dose electron micrographs of such crystals preserved in negative stain display order to 12-A resolution The crystal lattice is tetragonal (a = b = 992 +/- 14 A) with plane group symmetry p4g A projection density map at 12-A resolution defines the molecular boundary and organization of the CHIP28 monomers in the membrane plane The unit cell contains four CHIP28 dimers, each composed of two oblong-shaped (37 x 25 A ) monomers with opposite orientations The CHIP28 monomers associate to form tetrameric structures around the 4-fold axes normal to the membrane plane where stain is excluded The 2-D crystals of CHIP28 display order extending beyond the limit typically achieved by negative staining and therefore may be amenable to high-resolution structure analysis by cryo-electron microscopy
TL;DR: The current study demonstrates for the first time the effectiveness of using a slow-scan CCD camera for electron diffraction data collection from thin protein crystals at near atomic resolution.
TL;DR: In this article, the crystal structure, thermal vibrations, and electron density of leu-enkephalin trihydrate, C 28 H 37 N 5 O 7.3H 2 O, have been analyzed using single-crystal-X-ray diffraction data measured at 100 K with Mo Kα radiation to a resolution corresponding to [(sin θ)/λ]max=1.15 A -1.
Abstract: The crystal structure, thermal vibrations, and electron density of leu-enkephalin trihydrate, C 28 H 37 N 5 O 7 .3H 2 O, have been analyzed using single-crystal-X-ray diffraction data measured at 100 K with Mo Kα radiation to a resolution corresponding to [(sin θ)/λ]max=1.15 A -1 . A multipolar atom density model was fitted against the 5444 unique data with I>2σ(I) [R(F)=0.038, R w (F)=0.023, GOF=0.73] in order to calculate the phases for the crystal structure factors and map the valence electron distribution. Ab initio SCF calculations have been carried out on molecular fragments with extended basis sets including polarization functions
TL;DR: In this paper, the authors presented a high-resolution image of the starburst/Seyfert hybrid galaxy NGC 7469 using the Hale 5 m telescope at Palomar Observatory.
Abstract: We present a high-resolution 11.7 micrometer image of the starburst/Seyfert hybrid galaxy NGC 7469 using the Hale 5 m telescope at Palomar Observatory. Our map, with diffraction limited spatial resolution of 0.6 sec, shows a 3 sec diameter ring of emission around an unresolved nucleus. The map is similar to the Very Large Array (VLA) 6 cm map of this galaxy made with 0.4 sec resolution by Wilson et al. (1991). About half of the mid-infrared flux in our map emerges from the unresolved nucleus. We also present spatially resolved low resolution spectra that show that the 11.3 micrometer polycyclic aromatic hydrocarbon (PAH) feature comes from the circumnuclear ring but not from the nucleus of the galaxy.
TL;DR: This is the first high resolution structure of a complex between a ribosome-inactivating protein and a substrate analogue, in which the electron density of the N-glycosidic bond is well defined and the preassociated water, thought to be responsible for hydrolyzing the N -C bond, is also explicitly elucidated.
Abstract: Crystal structure of trichosanthin-NADPH complex at 1.7A resolution reveals active-site architecture
TL;DR: The potential of using the electron crystallographic approach for determining the 3-dimensional structure of the 50 S ribosomal subunit crystallized on a monolayer surface is illustrated and the structural information retrieved might be useful for phasing X-ray data towards an atomic resolution model of the ribosome.
08 Jan 1994-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the authors examine the time-focusing phenomena that occur in the operation of the crystal monochromator-Fermi-chopper time-of-flight spectrometer due to the correlation between transmitted wavelength and transmission time.
Abstract: We examine the time-focusing phenomena that occur in the operation of the crystal monochromator-Fermi-chopper time-of-flight spectrometer due to the correlation between transmitted wavelength and transmission time. Even with a flat monochromator the time-focusing has important consequences on the resolution width and on its dependence on the energy transfer. Time-focusing becomes critical for energy resolution with spatial focusing in the Bragg plane of the monochromator. We discuss the relation of the time-focusing conditions to the imaging conditions, object and image positions, and compare the analytically calculated resolution with simulation. Finally, the point of obtaining good wavevector transfer resolution through space focusing on the detector is presented.
TL;DR: This study resolves the differences between the analyses of the shape and size of the histone octamer structure and explains how the original electron density map could be converted to the new map by a phase modification in the Fourier synthesis.
TL;DR: A method for nonintrusive scanned near-field optical microscopy using an optical trap to position accurately a 50-100-nm-diameter lithium niobate particle by separation of the trapping and detection wavelengths so that objects that are transparent in the infrared may be positioned close to the particle, resulting in high resolution.
Abstract: We demonstrate a method for nonintrusive scanned near-field optical microscopy. The microscope utilizes an optical trap to position accurately a 50-100-nm-diameter lithium niobate particle. The infrared trapping beam is frequency doubled in the particle, resulting in a visible microscopic optical probe. By separation of the trapping and detection wavelengths, objects that are transparent in the infrared (e.g., biological) may be positioned close to the particle, resulting in high resolution. The current experimental resolution is limited to approximately 500 nm by the properties of the test objects. The theoretical resolution is less than 100 nm.
Patent•
25 Jul 1994
TL;DR: In this paper, an electron beam forming an electron image is formed by a support structure mounted in the path of the electron beam, with the support structure transmitting the electron image, and scintillating material is coated onto the side of the supporting structure opposite that on which the image is incident.
Abstract: An apparatus for improving the resolution of images produced by an electron microscope is provided and includes an electron beam forming an electron image, a support structure mounted in the path of the electron beam, with the support structure transmitting the electron image. Scintillating material is coated onto the side of the support structure opposite that on which the electron image is incident, the scintillating material converting the electron image into a light image. A mirror is provided for deflecting the optical path of the light image into a CCD camera positioned to receive and record the light image.
TL;DR: In this article, a high resolution spectrum of laser-produced plasma of aluminum in the range of 124-250 A with a spectral resolution of about 300 in the first order is presented.
TL;DR: In this article, the lateral and depth resolution of nonlinear microscopy was studied systematically, and it was shown that depth discrimination in Type I microscopy can improve with increasing nonlinearity, and the differences between coherent and incoherent imaging diminish.
Abstract: Summary
The lateral and depth resolution of nonlinear microscopy was studied systematically. Nonlinear microscopy can be classified into several categories depending on the coherence properties of the process that generates the imaging signal from the illuminating light, on whether a single- or a two-beam geometry is used, and whether the optical setup is Type I or Type II. An evaluation of the imaging equations shows that (i) lateral and depth resolution improve with increasing nonlinearity, (ii) the differences between coherent and incoherent imaging diminish, and (iii) nonlinear imaging allows depth discrimination in Type I microscopy.
TL;DR: In this paper, the k-space resolution function of a triple-crystal diffractometer is calculated for an arrangement of three perfect silicon single crystals Bragg diffracting in nondispersive Laue geometry.
Abstract: The k-space resolution function of a triple-crystal diffractometer is calculated for an arrangement of three perfect silicon single crystals Bragg diffracting in nondispersive Laue geometry. A comparison is made with the results of measurements using synchrotron radiation in the energy range from 80 to 150 keV. In this case, absorption is very weak and according to dynamical theory the width of the diffraction pattern of thick perfect single crystals is proportional to the wavelength λ, whereas its Lorentzian tails are proportional to λ2. Together with the fact that the Bragg angles are only of the order of 2°, this leads to a concentration of the starlike k-space resolution function into a narrow band parallel to the reciprocal-lattice vector G. For diffraction of 80 keV synchrotron radiation at the silicon 111 reflection, the full width at half-maximum (FWHM) of the intensity distribution in the scattering plane is 1.1 × 10−5 A−1 perpendicular to G and 2.2 × 10−4 A−1 parallel to G. The observed differences in the contributions from monochromator and analyzer crystal to the resolution function are explained by the finite width of the electronic window of the detector counting chain and the non-Bragg scattering contribution from the crystals. If annealed Czochralski-grown silicon single crystals with a mosaicity of ~3′′ are used as monochromator and analyzer, the resolution is reduced by one order of magnitude, but for studies of imperfect samples or of diffuse scattering large gains in intensity can be accomplished this way.
11 Aug 1994-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: MAXIMUM as discussed by the authors is a soft X-ray scanning photoemission microscope installed at the U41 undulator at the Synchrotron Radiation Center at the University of Wisconsin, which has demonstrated spatial resolution better than 0.1 μm and electron energy resolution of 300 meV.
Abstract: We present new results from the soft X-ray scanning photoemission microscope: MAXIMUM. The microscope is installed at the U41 undulator at the Synchrotron Radiation Center at the University of Wisconsin. The instrument is based on a multilayer-coated Schwarzchild objective, operating at 95 eV, and it has demonstrated spatial resolution better than 0.1 μm and electron energy resolution of 300 meV. We review the design and the implementation of the microscope. We also present recent results as well as a summary of the research programs that are being conducted with MAXIMUM.