Louis W. Labaw

Periodic structure in the flagella and cell walls of a bacterium.

Abstract Electron micrographs of a non-spore forming, gram-positive, motile bacterium show the peritrichous flagella to have an external contour of a counterclockwise double helix and the cell wall to have a rectangular periodic structure clearly visible on the inside surface. The flagella are about 150 A in a diameter and have a well-defined cross structure with a periodicity along the flagella axis of 155 A. The nearly constant angle (27 to 35 degrees) that the striae of this cross structure make with the normal to the flagellar axis requires the external contour of the flagella to be a double rather than a single counterclockwise helix. The periodic structure in the cell wall appears to be caused by a rectangular array of spheres or hemispheres having diameters of about 115 A. The outside of the cell wall shows only a faint suggestion of this periodicity.

Periodic structure in the flagella of Brucella bronchiseptica.

Abstract The flagella of the bacterium Brucella bronchiseptica have the external contour of a counter-clockwise of left-handed triple helix. The average periodicity along the length of the flagella was measured as 190 angstroms with the average diameter of the flagella measuring 139 angstroms.

Ox liver catalase crystal structure by electron microscopy.

A possible structure for dry ox liver catalase crystals has been deduced from a study of shadowed-replica and negatively stained preparations of two crystal habits. The gross features revealed in these preparations can be satisfactorily explained by assuming approximately spherical molecules about 73 A in diameter arranged in a rather open structure having the orthorhombic tetramolecular unit cell a = 73, b = 141, c = 183 A. An examination of the different amounts of distortion on drying and a study of the face angles on wet crystals of four habits indicate that the wet crystal structure is hexagonal with a bimolecular unit cell having the repeating unit along the unique axis equal to the particle diameter, D , and the other cell dimension (3) ½ D .

The structure of Bacillus Thuringiensis berliner crystals

The structure of the protein crystals formed by Bacillus thuringiensis Berliner, determined from electron micrographs of shadowed carbon replicas of dry crystals, can be described by a tetramolecular face-centered-cubic unit cell 123 A on an edge. The protein molecules appear to be spherical, with a diameter D = 87 A. The bipyramidal shape of these crystals results from their being bounded by eight similar (221) faces on which the rows of molecules are separated by 3 D. Membrane fragments made up of hexagonal arrays of spheres or ellipsoids whose average center-to-center separation is 68 A were common in the preparations examined and were believed to be a component of the cell walls.

The structure of southern bean mosaic virus protein crystals

Abstract From measurements on a series of electron micrographs of single crystals of the southern bean mosaic virus protein it is shown that their molecules are in a cubic close packed arrangement. The tetramolecular unit cube has the edge length a0 = 345 A corresponding to a dried particle diameter of 245 A. The various faces that appear on the crystals are identified and illustrated, and a possible relation suggested between their occurrence and the way the crystals have grown.

The electron microscopy of ferritin crystals

Abstract Electron microscopic observations on carbon replicas of dried crystals of the protein ferritin show that, within the limit of measurement, their molecules are in a cubic close packing with α 0 = 154A. The same arrangement has been found for the octahedra crystallized from 5% CdSO 4 and the flat plates from 1% CdSO 4 .

Further electron microscopic observations of bacteriochlorophyll protein crystals.

Two crystal habits of the bacteriochlorophyll protein from Chloropseudomonas ethylicum were examined using thin sectioning and negative staining. The previously published molecular packings were confirmed. The molecular shape suggested by these studies is a noncompact 81.5 A diameter sphere.

A new fibrous structure from fibrous tissue and fibroblasts

A structure that often looked like 200 A particles spaced 600–700 A apart along a thinner fiber was first found in bovine thyroid polyribosome preparations. Further experiments suggested that these strands were associated with connective tissue. Although the particle separation along the fiber was approximately the major spacing of native collagen and in some preparations the fiber between the particles showed beading somewhat similar to embryonic collagen, these strands were not collagen since they were unaffected by collagenase. In very clean preparations the fiber between the particles appeared to be a bundle of several smaller fibers.

The crystal packing of thyroglobulin.

Abstract The molecular packing in 19 s thyroglobulin crystals has been examined using shadowed, positively stained and negatively stained preparations. Crystallizing thyroglobulin molecules first form polymers which are right-handed helices with an average pitch of 228 A having four molecules per turn. The molecular shape appears to be approximately a sphere of 114 A diameter or a prolate ellipsoid of comparable volume. The three-dimensional packing of the helices can be described by an octamolecular orthorhombic unit cell having sides of 395, 228 and 197 A.

Electron microscopy of ultraviolet irradiated bacteria and their interaction with bacteriophage.

Abstract Electron microscopic observation shows that most bacteria in a suspension of E. coli receiving doses of ultraviolet light many times that sufficient to reduce plate counts of viable organisms 10 5 fold can grow and multiply for some time after irradiation. Evidence of this residual metabolism diminishes with increased dose of radiation. Such bacteria are lysed by bacteriophage with yields of new bacteriophage that also diminish with increased irradiation.