RADIATION BIOPHYSICAL STUDY OF BIOLOGICAL MOLECULES. Progress Report, September 1, 1970--January 31, 1972.

I should like to give you a very condensed progress report on some spectrophotometric measurements of objective-prism spectra made in collaboration with H. Leicher at Bonn. The procedure used is almost completely automatic. The measurements are made with the help of a semi-automatic fully digitized registering microphotometer constructed by Hög-Hamburg. The reductions are carried out with the aid of a number of interconnected programmes written for the computer IBM 7090, beginning with the output of the photometer in the form of punched cards and ending with the printing-out of the final two-dimensional classifications.

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Progress report on 21-cm observations at low latitude between longitudes (l 11) 0° and 66°

Symposium - International Astronomical Union ◽

10.1017/s0074180900100907 ◽

1967 ◽

Vol 31 ◽

pp. 177-179

Author(s):

W. W. Shane

Keyword(s):

Preliminary Report ◽

Progress Report ◽

Galactic Centre ◽

Low Latitude ◽

The Third ◽

Introductory Lecture ◽

Centre Region

In the course of several 21-cm observing programmes being carried out by the Leiden Observatory with the 25-meter telescope at Dwingeloo, a fairly complete, though inhomogeneous, survey of the regionl11= 0° to 66° at low galactic latitudes is becoming available. The essential data on this survey are presented in Table 1. Oort (1967) has given a preliminary report on the first and third investigations. The third is discussed briefly by Kerr in his introductory lecture on the galactic centre region (Paper 42). Burton (1966) has published provisional results of the fifth investigation, and I have discussed the sixth in Paper 19. All of the observations listed in the table have been completed, but we plan to extend investigation 3 to a much finer grid of positions.

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Elastic Scattering in Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071703 ◽

1973 ◽

Vol 31 ◽

pp. 252-253

Author(s):

J. Langmore ◽

M. Isaacson ◽

J. Wall ◽

A. V. Crewe

Keyword(s):

Electron Microscopy ◽

Elastic Scattering ◽

Cross Section ◽

Quantum Noise ◽

Dark Field ◽

Elastic Cross Section ◽

Biological Molecules ◽

Dark Field Microscopy ◽

Field Systems ◽

Effects Of Radiation

High resolution dark field microscopy is becoming an important tool for the investigation of unstained and specifically stained biological molecules. Of primary consideration to the microscopist is the interpretation of image Intensities and the effects of radiation damage to the specimen. Ignoring inelastic scattering, the image intensity is directly related to the collected elastic scattering cross section, σɳ, which is the product of the total elastic cross section, σ and the eficiency of the microscope system at imaging these electrons, η. The number of potentially bond damaging events resulting from the beam exposure required to reduce the effect of quantum noise in the image to a given level is proportional to 1/η. We wish to compare η in three dark field systems.

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3-D reconstruction of molecular shape from microcrystal thin sections

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100077311 ◽

1983 ◽

Vol 41 ◽

pp. 748-749

Author(s):

S. Cusack ◽

J.-C. Jésior

Keyword(s):

Three Dimensional ◽

Molecular Shape ◽

Biological Molecules ◽

Fourier Space ◽

Single Particles ◽

Thin Sections ◽

Standard Methods ◽

X Ray ◽

X Ray Crystallography ◽

Dimensional Reconstruction

Three-dimensional reconstruction techniques using electron microscopy have been principally developed for application to 2-D arrays (i.e. monolayers) of biological molecules and symmetrical single particles (e.g. helical viruses). However many biological molecules that crystallise form multilayered microcrystals which are unsuitable for study by either the standard methods of 3-D reconstruction or, because of their size, by X-ray crystallography. The grid sectioning technique enables a number of different projections of such microcrystals to be obtained in well defined directions (e.g. parallel to crystal axes) and poses the problem of how best these projections can be used to reconstruct the packing and shape of the molecules forming the microcrystal.Given sufficient projections there may be enough information to do a crystallographic reconstruction in Fourier space. We however have considered the situation where only a limited number of projections are available, as for example in the case of catalase platelets where three orthogonal and two diagonal projections have been obtained (Fig. 1).

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Direct visualization of phase-separated domains in lipid membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100082315 ◽

1978 ◽

Vol 36 (2) ◽

pp. 290-291

Author(s):

S. W. Hui ◽

T. P. Stewart

Keyword(s):

Lipid Membranes ◽

Structural Information ◽

Freeze Fracture ◽

Biological Molecules ◽

Vacuum Drying ◽

Direct Visualization ◽

X Ray Diffraction ◽

Electron Microscopic ◽

X Ray ◽

Hydrocarbon Chains

Direct electron microscopic study of biological molecules has been hampered by such factors as radiation damage, lack of contrast and vacuum drying. In certain cases, however, the difficulties may be overcome by using redundent structural information from repeating units and by various specimen preservation methods. With bilayers of phospholipids in which both the solid and fluid phases co-exist, the ordering of the hydrocarbon chains may be utilized to form diffraction contrast images. Domains of different molecular packings may be recgnizable by placing properly chosen filters in the diffraction plane. These domains would correspond to those observed by freeze fracture, if certain distinctive undulating patterns are associated with certain molecular packing, as suggested by X-ray diffraction studies. By using an environmental stage, we were able to directly observe these domains in bilayers of mixed phospholipids at various temperatures at which their phases change from misible to inmissible states.

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Correction of the contrast transfer function to determine the radial density distribution of frozen-hydrated tobacco mosaic virus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100123088 ◽

1992 ◽

Vol 50 (1) ◽

pp. 536-537

Author(s):

Michael F. Smith ◽

John P. Langmore

Keyword(s):

Transfer Function ◽

Phase Contrast ◽

Heavy Atom ◽

Biological Molecules ◽

Frequency Compensation ◽

Contrast Transfer Function ◽

High Background ◽

Low Contrast ◽

Radial Density Distribution ◽

Excellent Preservation

The purpose of image reconstruction is to determine the mass densities within molecules by analysis of the intensities within images. Cryo-EM offers this possibility by virtue of the excellent preservation of internal structure without heavy atom staining. Cryo-EM images, however, have low contrast because of the similarity between the density of biological material and the density of vitreous ice. The images also contain a high background of inelastic scattering. To overcome the low signal and high background, cryo-images are typically recorded 1-3 μm underfocus to maximize phase contrast. Under those conditions the image intensities bear little resemblance to the object, due to the dependence of the contrast transfer function (CTF) upon spatial frequency. Compensation (i.e., correction) for the CTF is theoretically possible, but implementation has been rare. Despite numerous studies of molecules in ice, there has never been a quantitative evaluation of compensated images of biological molecules of known structure.

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