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SUMMARY Easy preparation of thin crystalline specimen supports for high resolution electron microscopy has been achieved by thermic exfoliation of vermiculite. The thinnest layers obtained appear to be 1·8 nm thick and show the expected hexagonal array with a 0·46 nm lattice spacing. This periodic background could be suppressed either by optical filtering or by putting a zero crossing of the respective transfer function of the electron microscope objective over the diffraction spots of the crystal.

The development of the electron microscope microanalyser (EMMA 4) is briefly reviewed. It is pointed out that while in principle any ultra-thin specimen can be examined, chemical treatment will remove certain substances. In this connection, the use of EMMA 4 has been helped by developments in cryo-ultramicrotomy. While at present elements lighter than sodium cannot be detected there is nothing in principle to prevent the range from being extended to elements of lower atomic number.

The imaging improvement method recently proposed by Stroke and Halioua for conventional electron microscopy has now been successfully demonstrated with an electron micrograph of a T2 bacteriophage virus originally photographed with heretofore unsurmountable “blurring” characteristic of defocusing phase contrast.

Images of the (001) planes of muscovite were observed by electron microscopy after embedment of clay-size flakes in epoxy resin and sectioning by ultramicrotome. Dislocation or growth planes were indicated. Incomplete exchange of potassium for barium produced zones with 20-angstrom periodicity, suggesting regular interstratification.

Die prinzipielle Konstruktion eines neuen Mikrotoms zur Herstellung ultradunner Schnitte wird beschrieben. Mit diesem Mikrotom sind Schnitte hergestellt worden, die dunner als 100 A waren.

The phase contrast transfer function (CTF) for imaging of weak phase objects in high resolution electron microscopy is well known. It is an oscillating function, generating transfer intervalls with positive and negative contrast. Due to the influence of chromatic aberration and partial coherence its amplitude decreases at higher spatial frequencies. Several attempts have been made to improve the CTF by a posteriori optical filtering, e.g. zonal filtering or the use of Tsujiuchi-type phase filters. The method of holographic deconvolution, as proposed by Stroke and Halioua, employs phase and amplitude filters in such a way that the CTF approaches nearly a constant value.

A high resolution electron microscopy investigation has been undertaken in order to obtain additional information regarding the nature of the strain field of small defects (∼10–75 A diameter) produced in copper and copper-16 atomic per cent aluminum crystals by neutron irradiation and by bombardment with 40 keV Cu+ ions. In addition to bright and dark field observations at electron optical magnifications of 250,000–425,000 ×, lattice fringe images were obtained in the vicinity of the radiation produced defects by combining the transmitted beam with one of the diffracted beams. It was found that some of the defects had a principal strain component along only one 〈111〉 whereas other defects had a more complex strain field with strain components along more than one direction. For those defects with a principal strain component along only one 〈111〉, the localized defect concentration in a collision cascade may be sufficiently high for the spontaneous formation of a Frank dislocation loop to occur. In...

High-resolution electron microscopy of the particles of tobacco mosaic virus has been undertaken in an attempt to elucidate the details of the surface contours of these objects. Some techniques have been developed to aid in the consistent attainment of resolutions better than 3 mμ in micrographs of shadowed virus particles. These developments bear upon the problems of mechanical stability of the specimen, and of contamination of the specimen in the electron microscope. The routine use of polystyrene latex particles is discussed in connection with the problem of the evaluation of the excellence of electron micrographs. Observations have been made of the surface structure of the particles of tobacco mosaic virus in normal preparations, and in freeze-dried, incinerated, and sonicated preparations. It is concluded that no evidence exists of periodic surface structure, either transverse or longitudinal. Sonicated preparations provide thin platelets which have been broken cleanly in planes transverse to the axis of the rods. When these platelets are observed perpendicular to their planes, they exhibit hexagonal cross-sections of varying degrees of perfection of figure. The failure of the normally observed rods of TMV to appear hexagonal is discussed. Evidence is given which indicates that some sort of creeping of the shadowing uranium film exists, and that consequently the surface appearance of rods lying on their sides on the substrate film has little bearing upon their true contours. It is suggested that a film of adsorbed oil from the vacuum pumps of the shadowing apparatus is the cause of the apparent surface mobility of the uranium atoms. It is concluded that the shape of the normal rods of tobacco mosaic virus is that of an elongated hexagonal prism.

The interfaces between narrow augite exsolution lamellae and enstatite matrix are examined in detail by transmission electron microscopy using weak-beam and direct lattice imaging techniques. Direct observation of matrix planes with a (100) interplanar spacing (18–3 A) and the (200) lamella planes (4–6 A) at the interface between the two phases reveals steps or ledges usually one atomic plane high every few hundred Angstroms; growth of a lamella apparently involves the motion of ledges parallel to the interface. Terminating (200) lattice fringes, indicating the presence of a dislocation, are observed at each ledge. The dislocations, which are parallel to [010], also have an [001] component that stabilizes the structure by reducing the strain energy of the interface.

A simple technique has been developed for the study of the external form and structure of virus particles. High contrast with good preservation is obtained by mixing virus preparations with 1% phosphotungstic acid adjusted to pH 7.5 and spraying directly onto electron microscope supporting films made from evaporated carbon. The application of the technique to tobacco mosaic virus and turnip yellow mosaic virus is described. Structural details suggested by X-ray diffraction methods have been resolved.

The defect structure of TiO 2 ·7Nb 2 O 5 has been examined at about 0.3 nm resolution in an electron microscope. Under suitable conditions of crystal orientation and objective lens defocus, the contrast in images from very thin fragments can be interpreted directly in terms of structure. Proposed structures for Wadsley intergrowth defects and displacements are confirmed, and new observations of complex fault bands and grain boundaries are described. Microdomains of TiNb 14 O 37 , with the structure predicted by Wadsley, have also been found in this material.

Low-temperature specimen stages are advantageous for various applications of electron microscopy. The problems arising in the construction of such devices are surveyed and solutions involving some new principles and methods are indicated. These are discussed for the case of a helium-cooled stage constructed for a Hitachi high-voltage electron microscope. This device allows cooling in the temperature range from 300 to 5 K under full preservation of the optical resolution of the microscope. The fundamentals of the construction may easily be applied to the construction of cooling stages for other microscopes. The new cooling stage presented here has the following main features. Highly concentric mounting is ensured by using isolating hollow cylinders as supports. The specimen can be tilted +or- 30 degrees in each direction and can be translated +or- 1 mm in all directions perpendicular to the electron beam. Specimen exchange is simple and requires merely the insertion of a light specimen holder into the stage via an airlock mechanism. A vibration-free and thermally extremely stable cooling is achieved over the whole temperature range by using cold helium gas.

In electron microscopy the detection of fine detail is limited by the structure of the supporting film. Procedures have been developed to convert conventional evaporated carbon films into graphitic ones by a high temperature heat-treatment in an inert Argon atmosphere. Temperatures of about 2700°C yield crystallites a few tenths of a micron across, the size increasing somewhat with film thickness. The graphitised films proved very appreciably smoother than the untreated ones. This difference was readily detected in the high vacuum, high resolution scanning electron microscope of Crewe and Wall (1970), but only erratically in conventional electron microscopes.

The desirability and requirements for a specimen capable of testing the resolving power and other image characteristics of an electron microscope are discussed in detail. In this discussion, the underlying diffraction phenomena are particularly utilized. A partially graphitized carbon black is shown to satisfy the requirements extremely well and constitutes an easily prepared specimen for conducting tests of image quality in the molecular size range. The structure of the test object is known in detail with the result that readily interpretable phase contrast images are obtained. Micrographs illustrating the use of the 3.4 A (002) spacing for magnification calibration, astigmatism and asymmetry check as well as resolving power are exhibited. The second order c-spacing of 1.7 A is occasionally found in an image. The micrographs shown herein were taken with two different electron microscopes by different operators obtaining the same structural detail in the images. It is concluded that the carbon black test object offers the best possibilities for evaluating image performance of any specimen yet suggested.

The ultrastructure of the cells of the proximal convoluted tubules of the mouse kidney has been studied by means of electron microscopy at a fairly high resolution (35 A) on ultra-thin sections. The tissue was fixed in buffered (pH 7.2) osmium tetroxide according to Pallade and embedded in n-butylmethacrylate. 1. 1. Towards the basement membrane the cell membrane appears as a thin zone of condensed cytoplasm. An about 200 A wide space separates this cytoplasmic zone from the basement membrane. Between adjacent cells the separating membrane consists of an about 160 A thick double membrane, which connects to the “brush border” structure. 2. 2. The cytoplasm of the basal cell zone is divided into compartments by means of double membranes here called intracellular cytoplasmic membranes. They surround the mitochondria and at the basal cell surface they assist in lining the cytoplasm towards the basement membrane. The mean thickness of these membranes is 270 A, the thickness of each constituent single membrane is 80 A and the height of the space in between the two membranes is 110 A. 3. 3. The mitochondria are rod-shaped. They are lined by a 160 A thick double membrane consisting of two about 45 A thick membranes separated by a 70 A wide space. In the interior of the mitochondria there are transversally oriented double membranes organized in a similar way as the outer mitochondria membrane and mutually separated by 170–470 A wide spaces. Between these internal membranes areas exhibiting a pronounced contrast due to a heavy reduction of osmium tetroxide may be found. 4. 4. The “brush border” consists of densely arranged cylindrical “ducts.” The “ducts” are 600 A wide and 1.0–1.5 μ long and lined by a thin dense wall. These ducts are closed towards the tubular lumen. They are also closed at their base where the walls continue in curved rods. The “ducts” are oriented perpendicularly to the cell surface facing the lumen and in cross sections they closely resemble the structure of a honey-comb with the exception that the tubes approach a circular, more than a hexagonal cross section. 5. 5. In the intermediate cell zone there are granules and vacuoles, corresponding to the previously described fluorescent granules (18). These structures exhibit a well marked membrane surrounding the vacuole or the granule. The granules contain inner granules which are extremely dense due to heavy reduction of osmium tetroxide. The granules of this cell zone correspond to the osmium tetroxide reducing granules observed in the light microscope and which have been classified as constituting the Golgi apparatus of these cells. 6. 6. The nuclei are lined by a 230 A double membrane, the constituent single membranes measuring 60 A in thickness and the height of the space in between these single membranes 100 A. 7. 7. The structure of the characteristic double membranes observed as cell membranes, intracellular cytoplasmic membranes, outer and inner mitochondria membranes and nuclear membranes is discussed and it is tentatively assumed that they are composed of two protein membranes separated by multilayers of lipid molecules.

Mafic chlorite from Benton, Arkansas was comminuted by rotary blending of a suspension, and the -- 2 ~m fraction separated by sedimentation in H~O. Droplets of suspension of the < 2 ~m fraction were dried on a layer of Epoxy resin and then addit!onal Epoxy was added and heat-cured at 48~ to form a resin sandwich. Cross-sections of 600-900 A thickness were cut on a Reichert auto- mated ultramicrotome. The sections were collected on standard electron microscope specimen screens, reinforced by vacuum evaporated C and examined by transmission electron microscopy (TEM). The Phillips EM 200 electron microscope was equipped with a "microgun" source to minimize heating of the specimen and to improve contrast and high resolution (HREM). Images of the (001) chlorite crystallographic planes spaced at 13.9A intervals were visible on many of the particle sec- tions. Imaging of the planes depended upon their being nearly parallel to the electron beam (within 0 ~ 10') and therefore, many particles which had other orientations did not show the 13.9A image. Micrographs made beforeoappreciabte irradiation by the electron beam revealed images of fringes corresponding~ to the 7-22 A (002) spacing of chlorite. Loss of the 7.22 ~ fringes and reinforcement of those at 13.9A resulted from heating of the chlorite in the electron beam. This behavior is analogous to the well-known crystallographic effects of heating chlorite at 550-760~

It is now possible to resolve the basic periodicity of the arrangement of atoms or molecules in crystal lattices using the electron microscope. Examples are given of lattices resolved directly (including superlattices), and indirectly (by means of moire patterns) and of other periodic phenomena associated with crystal lattices (domains in ordered alloys). The basic principles of image formation in periodic objects are considered in terms of simple diffraction theory and some indications given of limiting factors in this type of investigation.

The resolving power of the electron microscope which is required for a direct read out of atomic structures in real specimens is considerably smaller than the average interatomic spacing. This is due to the overlapping of the more or less defocused projection images of those atoms which do not lie in the plane of optimum focus. Thus, with the best present-day microscopes, which have a resolving power of about 0.2 nm and an accelerating voltage of about 100 kV, atom positions can be observed only in monolayer specimens. If more than one layer is present the intensity distribution is only a measure of the projection image density. Because of the objective aperture being directly proportional to the electron wavelength and inversely proportional to the resolving power the depth of focus strongly depends on both these quantities. Approximation formulae for limit of resolution imaging conditions have been derived. They show that in order to obtain a direct read out of the atomic structure of a specimen of only 2 to 3 nm thickness a mega volt electron microscope should be used, and the required resolving power is as low as a fraction of the average atomic spacing. If the resolving power is improved for microscopes in the 100 kV range the depth of focus will decrease so rapidly that the optimum specimen thickness finally turns out to be less than 1 nm. A small amount of chromatic aberration can produce an effective enlargement of the depth of focus for accelerating voltages U < 500 kV, but this gain is purchased by an order of magnitude increase of the background intensity. This in turn deteriorates the signal: noise ratio, and the electron dose required to transmit the image information is considerably larger with U < 500 kV voltages than in the megavolt range, leading to correspondingly larger radiation damage.

ALTHOUGH electron microscope contrast may be increased by the use of objective apertures, accurate focusing in thin-section work is still difficult and, in order to obtain an in-focus picture of a particular field, it is very helpful to find a small dense particle, or a hole in the membrane, on which to focus. An obvious solution to this problem is to distribute small dense particles on the specimen.

In preparations of sap removed from sugar beet infected with beet yellows virus, filaments have been concentrated in sufficient numbers to be studied in the electron microscope. Using the negative staining technique, the virus appears as a filamentous structure 10 m μ in diameter and one to several microns long. The filaments have a regular periodicity and a central hollow core. Small hollow particles 10 m μ in diameter, observed in infected sap, may be short pieces of filament. The methods of preparation are discussed and dimensions compared with tobacco mosaic virus.

The detailed structure within the two‐dimensional projection of the unit cell of a Ti2Nb10O29 crystal, showing the arrangement of the metal atoms, has been revealed by careful use of a high‐resolution electron microscope. The image shows good agreement with the model of the structure deduced from x‐ray diffraction studies.

Recent developments in the techniques of high-resolution electron microscopy have allowed the direct visualization of heavy-atom positions in crystal lattices. The detailed structures of ordered phases and the atom configurations in planar, linear, and point defects have been indicated with a resolution of about 3 A for a number of oxides of niobium and mixed oxides containing titanium, zirconium, and tungsten. Much the same information is available for a number of minerals. Indications of the mechanism of phase transformation can be derived in some cases from studies on quenched samples or by observation of changes induced by electron irradiation. Some information can be obtained regarding the state of short-range order in relatively simple systems by the use of dark-field imaging techniques in combination with electron-diffraction observations.

High resolution electron microscopy with superconducting lenses at liquid helium temperatures

β-Galactosidase, a lactose-splitting enzyme of high molecular weight, was isolated from Escherichia coli ML 308. The crystalline enzyme was investigated by electron microscopy using the negative staining technique. Two structural patterns were commonly observed and interpreted to represent different orientations of the molecule. The size and shape of unfixed molecules and molecules fixed in formaldehyde solution were compared. A subdivision into four subunits was indicated for the molecule in the amorphous state. The molecular weight calculated from the observed dimensions of the molecule was estimated to be about 500,000. A substructure of the subunit was indicated. The molecule has been found to be asymmetric with regard to its quaternary structure.

Publisher Summary Improvements in specimen preparation techniques and instrumentation have made it possible to perform high-resolution electron microscope and electron diffraction studies of biological systems under conditions approaching the hydrated native state. As a result of the better morphological and histochemical preservation achieved by these techniques, including liquid-helium cryofixation and related low-temperature methods, previously undetected unit components have been observed in the plane of the layers of photo-receptors and related lamellar systems. Correlated electron-microscope and biochemical studies of mitochondrial membranes have resulted in the detection and isolation of a fundamental unit of energy transduction, corresponding to the respiratory enzyme assemblies in mitochondrial membranes. Enhanced contrast and resolution of the order of 8A were achieved in direct studies of the macromolecular organization of τ2 bacteriophage particles, ribosomes, and of isolated cell constituents. Electron microbeam probes, measuring only 100 to 1,000 A in diameter, have also been applied in controlled irradiation of selected minute regions of hydrated systems containing DNA, including the head portion of single bacteriophage particles and viable bacterial spores.

The alteration of organic materials during burial is similar to thermally induced carbonization. High resolution electron microscopy shows that samples of either natural or heat-treated kerogens are formed by stacks of two aromatic layers of 5–8 A in diameter. During catagenesis and heat-treatment, these stacks orientate themselves parallel to each other and form clusters of increasing diameter.

A critical survey of the published data of the focal properties of magnetic electron lenses has revealed several inconsistencies between the findings of various authors. Some of these can be ascribed to errors in computation, but others stem from inherent limitations imposed by the conventional presentation of results in the form of `universal' curves or from the use of relative rather than fixed units, such as centimetres. The results of more accurate computations, especially of spherical aberration, are presented in a new form which is particularly suited to the determination of lenses of optimum performance. The results are applied to the question of determining the best possible objective lens for high resolution electron microscopy.

Heat treatment of MgF2, Nb2O5 mixtures has been used to form complex oxides possessing „block structures”. By means of high resolution electron microscopy it is possible to observe the component blocks and to identify defects at the unit cell level. Interaction of planar defects within such crystals gives rise to anomalous structures, including hitherto unreported extended linear defects in the form of rectangular tunnels. Their cross-section, 2.8 × 5.6 A2, is within the resolving power of the electron microscope and at the appro-priate defocus they appear as white streaks in the lattice image. [Russian Text Ignored].

High resolution electron microscopy has been used to examine thin films of natural rubber and other polymers. Dispersions of various materials (in particular neoprene and chlorinated natural rubber) in natural rubber have been studied. Structures which are believed to be the individual curled-up molecules of the dispersed polymer have been photographed. Stretched rubber films have also been examined and some information about the mode of deformation obtained.

The results obtained by the application of five different methods to stain with silver methenamine thin sections of tissue for electron microscopy are described and evaluated in this article. Three of these methods lend themselves to wide applications in that they enhance vividly the argentophilic structures without inducing excessive graininess of the staining. The latter appears to be due mainly to prolonged and unnecessary exposure of the sections to the staining solution. The graininess observed in specimens prepared under the most favorable conditions, however, is still too coarse to allow the application of this technique for high resolution electron microscopy.

With the use of high-resolution electron microscopy, defects have been observed in crystals of Nb22O54: two types of point defects and extended Wadsley-type defects having a structure corresponding to Nb12O29. For one type of point defect a model is proposed which contains two displaced metal atoms and two interstitial oxygen atoms within a 'block'. For the other, one metal atom and three oxygen atoms are considered to be missing from a tetrahedral site. Contributions made by the three types of defects to the non-stoichiometry of the crystals are discussed.

In the evaluation of an iterative scheme that determines the amplitude-phase distribution of an image from two image intensity distributions recorded at two different lens defocus values, the effects of various sources of error on the solution for the phase distribution are examined, namely, a background signal superimposed on the image intensity, a mismatching of the two images and an error in determining the defocus difference between the two images. In electron optics, a background intensity, arising from (say) inelastic electron scattering, corresponding to 10% of the maximum image intensity has a significant effect on the calculated phase distribution. In high-resolution electron microscopy, achieving a potential image resolution of 01-03 nm, a mismatching of the two images by 01 nm is acceptable, corresponding to a misalignment of the two electron micrographs by 50 μm at an electron-optical magnification of 500 000; and a defocus error of 10 nm, in a total defocus difference of 100 nm between the two images, does not severely distort the solution for the phase distribution. The combined effect of photographic noise (10-20% of the maximum intensity), mismatching (01 nm), defocus error (10 nm) and a background (6% of the maximum intensity) on the calculated phase distribution gives an indication of the maximum error that can be tolerated in an experimental test of the method. The magnitude of the maximum error that can be tolerated may be scaled to the resolution required in the phase solution and the wavelength of the radiation used; in optics with a potential image resolution of 10 μm, a mismatching of images by 5-10 μm (at unit magnification or 05-10 mm at an optical magnification of 100) is acceptable and a corresponding defocus error of 100 μm for a defocus difference of 1 mm (depending on the numerical aperture of the objective lens).

Freshly excised skeletal muscle, in cold 50mM CaCl2, is briefly and repeatedly treated with a Waring Blendor to produce many segments from the cylindrical muscle cells. Straining through terylene netting removes connective tissue. The muscle-cell segments are washed free of CaCl2 with 25mM NaCl at pH 7.4 and then incubated at 37° for 30 min. After these steps the addition of water to the cell segments produces an abrupt and dramatic dissolution of the remaining intracellular proteins, washing out all intracellular structures and leaving behind the membranes as empty, thin-walled tubes. These membranes are concentrated and separated by brief centrifugations. Light microscopy reveals no structure in the membranes but electron microscopy shows that they consist of a fibrillar network overlying an amorphous layer. The dramatic dissolution in water of the proteins within the cell segments is believed to be due to a breakdown of an internal structure which normally protects the proteins against the solvent action of water. The breakdown is accelerated by incubation at 37°. Two problems concerning the method remain, namely, ridding the membranes of adherent capillaries and ascertaining by high resolution electron microscopy the membrane components recovered.

Typical gold sol particles were examined by high-resolution electron microscopy to study the nucleation and growth mechanism. The samples of colloidal gold were Faraday sol, Weimarn sol and sodium citrate sol, whose average particle diameters were estimated to be 55.2 ± 10.6 A, 131 ± 13 A and 154 ± 70 A, respectively. The shape of particles is mostly spherical excepting some of the Weimarn sol which includes pentagons with some round apices. The high resolution electron micrographs taken at a magnification of 125,000 times clearly show that the majority of the particles consist of smaller elementary crystallites with sharp boundaries which appear as parallel or radial lines defined by distinct diffraction contrasts. Moire fringes of 5–8 A spacings as well as crossed lattice images of 2.03 and 2.35 A due to (200) and (111) reflections were also observed. Systematic analyses of these contrasts indicated that the particles are formed by parallel or radial twins with definite mutual orientations. The origin of the fine structure can be attibuted to the nucleus interactions which precedes the actual growth in the early stage of sol formation. The possibility of the formation of metastable nuclei with icosahedral configuration which grow into the multiple twins and the successive transition to the natural cube-octahedral nuclei which after mutual interactions lead to the parallel twins was also discussed.

Cardiolipin, when placed in saline solutions, forms lamellar vesicles of varying complexity and size (600 A-3.0 μ ). When examined with high resolution electron microscopy, periodic structures consisting of alternating light and dark bands with a repeat distance of 50 A can sometimes be resolved. Upon sonication the vesicles break into smaller particles (250–1500 A) and appear generally as unilamellar structures. However, certain spherules can be found in which an apparently single lamella separated into two bands of less than 30 A thickness. These findings are interpreted in terms of a bimolecular lipid leaflet with osmium deposited in the hydrocarbon portion. In some cases electron dense material, presumably osmium precipitates, can be seen in an area between the two bands where they lie in close proximity to each other. The periodic structure observed in unsonicated preparations is thought to be the result of accumulation of relatively greater amounts of OsO 4 between bilayers of close proximity.

In the electron microscope, a repeating pattern of minute striations has been observed within hydroxapatite crystals. This fringe pattern can be explained as projections of planes of atoms or molecules on the image plane with a periodicity equal to the spacing between these planes in the crystal lattice. Previous studies have reported a pattern of 8.2 A repeat periods in hexagonal crystals of young rat enamel, representing the resolution of the 100 planes of the hydroxyapatite crystal lattice. In the present study, fringe patterns were demonstrated in crystals of human enamel, dentin, cementum, and bone tissue. When the incident electron beam was parallel to thec axis, the three sets of equivalent lattice planes parallel to this axis could be resolved simultaneously. Even those crystals which had an unusual external form showed a substructure that consisted of arrays of straight lines. Defects of the fringe pattern indicating dislocations or stacking faults in the crystal lattice were occasionally observed, in particular near the midline of the crystals. Thus, it appears possible to demonstrate visually not only variations in crystal size and shape but also the presence of lattice defects within individual apatite crystals. By high resolution electron microscopy it may prove possible to correlate the crystallinity of bone and tooth apatites to the fine structure of these tissues in normal and pathological conditions.

The ultrastructural organization of the fibrous component of amyloid has been analyzed by means of high resolution electron microscopy of negatively stained isolated amyloid fibrils and of positively stained amyloid fibrils in thin tissue sections. It was found that a number of subunits could be resolved according to their dimensions. The following structural organization is proposed. The amyloid fibril, the fibrous component of amyloid as seen in electron microscopy of thin tissue sections, consists of a number of filaments aggregated side-by-side. These amyloid filaments are approximately 75–80 A in diameter and consist of five (or less likely six) subunits (amyloid protofibrils) which are arranged parallel to each other, longitudinal or slightly oblique to the long axis of the filament. The filament has often seemed to disperse into several longitudinal rows. The amyloid protofibril is about 25–35 A wide and appears to consist of two or three subunit strands helically arranged with a 35–50-A repeat (or, less likely, is composed of globular subunits aggregated end-to-end). These amyloid subprotofibrillar strands measure approximately 10–15 A in diameter.

The submicroscopic organization of the retinal rods of the rabbit has been studied with high resolution electron microscopy in thin longitudinal and cross-sections. The outer rod segment consists of a stack of flattened sacs or cisternae each of them limited by a thin homogeneous membrane of about 30 A. The membrane of the rod sacs is attached to the surface membrane and is also in continuity with short tubular stalks of about 100 to 150 A which apparently end in relation with the connecting cilium. The bundle of filaments that constitute the connection between the outer and the inner segments is described under the name of connecting cilium. This fibrous component has a structure that is very similar to that of the cilium. It shows 9 pairs of peripheral filaments of about 160 A in diameter, a matrix material, and a surface membrane. Very infrequently two central single filaments are observed. The connecting cilium has a typical basal body in the inner segment; its distal end penetrates the outer segment, where it establishes some structural relation to the rod sacs. The relationships and submicroscopic organization of the connecting cilium were studied in longitudinal and in cross-sections passing at different levels of the rod segments. The inner rod segment shows two distinct regions: a distal and a proximal one. The distal region, corresponding to the ellipsoid of classical histology is mainly composed of longitudinally packed mitochondria. It also contains the basal body of the cilium, vacuoles of the endoplasmic reticulum, dense particles, and intervening matrix with very fine filaments. In the proximal region of the inner segment the mitochondria are lacking and within the matrix it is possible to recognize elements of the Golgi complex, vacuoles of the endoplasmic reticulum, dense particles and numerous neuroprotofibrils of 160 to 200 A in diameter which collect and form a definite bundle at the exit of the rod fiber. The interpretation of the connecting fibers as a portion of a cilium and of the outer segment as a differentiation of the distal part of a primitive cilium are discussed. The importance of the continuity of the surface membranes of the outer segment, connecting cilium, and inner segment is emphasized and its possible physiological role is discussed.

The hydrolysis products of zirconyl chloride, produced by reflux of a 0.055 M solution, have been studied by high-resolution electron microscopy. Removal of samples of the solution at various stages of hydrolysis, together with examination of the solids obtained by rapid dehydration of these samples, has enabled structural units consistent in size with the tetrameric cation [Zr(OH) 2 4H 2 O] 4 8+ to be resolved in the electron microscope. These data indicated that there were species present in solution similar to those present in crystalline zirconyl chloride octahydrate. Later stages of the hydrolysis produced polymerization of these species until monoclinic ZrO 2 was obtained. A suggested mechanism relating these various structures was supported by pH measurements taken during the hydrolysis.

High-resolution electron microscopy is integrated with physicochemical methods in order to investigate the following preparations of the giant nerve fibers of the squid (Loligo pealii L.): (1) Thin sections of fibers fixed in four different fixatives; (2) fresh axoplasm stained negatively in solutions of different pH and composition; (3) chemically isolated threadlike elements of the axoplasm. A continuous, three-dimensional network can be identified in all these preparations of the axoplasm. The network is composed of coiled or looped unit-filaments approximately 30 A wide. The unit-filaments are intercoiled in strands approximately 70-250 A wide. The strands are oriented longitudinally in the axoplasm, often having a sinuous course and cross-associations. Microtubules are surrounded by intercoiled unit-filaments and filamentous strands. Calcium ions cause loosening and disintegration of the network configuration. UO(2) (++) ions of a 1% uranyl acetate solution at pH 4.4 display a specific affinity for filamentous protein structures of the squid giant nerve fiber axoplasm, segregating the filamentous elements of the axoplasm in a coiled, threadlike preparation. The uranyl ions combine probably with the carboxyl groups of the main amino acids of the protein-glutamic and aspartic acids. It is proposed that by coiling/decoiling and folding/unfolding of the unit-filaments, shifts in physicochemical properties of the axoplasm are maintained.

Homogenates of eggs and embryos from three species of sea urchin contain large quantities of a protein whose presence is revealed by its ultraviolet absorption in sedimentation profiles. The material sediments homogeneously at 27 S in several media at neutral pH. It is free of nucleic acids, egg pigments, and of Cu, Fe, and Zn. The protein has been crystallized and examined by negative staining and high resolution electron microscopy. The 27 S material has a molecular weight of 894,000, as determined in the ultracentrifuge by the approach to equilibrium method, and a complex internal structure revealed by the electron microscope. The particle is a parallelepiped, and its exterior dimensions average 125 × 180 × 90 A. This material arises during homogenization of the cells from the rupture of large and abundant subcellular particles, probably yolk.

By the use of Araldite as an embedding medium, ultra-thin sections of fully-keratinised wool fibres have been obtained suitable for high-resolution electron microscopy. The bilateral structure of the cortex of Merino wool-fibres was observed due to the greater abundance in the orthocortex of residual cytoplasmic protein. This protein is osmiophilic and is dissimilar in structure and properties to keratin. It finally locates itself between the macrofibrils. This difference in structure of the two segments at the histological level probably explains the greater accessibility of the orthocortex to dyes. Large gaps up to 300 A wide are present between the cells both in the cortex and in the cuticle. These gaps are filled with a morphologically well-defined cementing material. The chemical reduction of the most reactive disulphide bonds of the fully-keratinised wool-fibre (the “A + B” fraction of the cystine content) followed by prolonged treatment with OsO4 resulted in electron micrographs which support the “microfibril + matrix” model for α-keratin structures. Morphological and chemical evidence is also adduced which indicates that the matrix is rich in sulphur. The microfibrils were observed to pack in various ways. In the paracortex, near perfect hexagonal packing was seen, intermixed with areas of irregular packing, and packing into layers. In the orthocortex the microfibrils are arranged into whorls.

To determine the location of grafted poly(methyl methacrylate) in orthocortex structure of fine Australian Merino wool fibers, high-resolution electron microscopy was used. Optimal staining conditions for the observation of the deposited polymer were also studied. It was supposed that the grafted polymer is located mainly between the microfibril and matrix and around the protofibrillar subunits, but not in the matrix. The average space occupied by a grafted chain was estimated to be about four times as large as the total residue volume per polymer. It is supposed that the remarkably large space available per polymer chain is related to the excessive swelling seen with respect to the polymer uptake.

By rapid quenching from the melt, using the splat forming gun technique, a noncrystalline phase has been obtained in a Cu-Zr alloy containing 60 at. pct Cu. Upon heating, rapid crystallization of the samples takes place at 477°C with a heat release of about 700 cal per mol. The variation of the electrical resistivity of the samples with temperature confirms the transformation. Very high resolution electron microscopy studies of the structural changes of the samples, at 3 × 106 magnification, upon heating are presented and show the gradual crystallization of the amorphous structure.

The solution of the two-dimensional convolution integral is presented for the case when the experimental results are subject to error. In particular, a resolution kernel whose Fourier transform has zeros is considered. This corresponds to resolution functions obtained in high-resolution electron microscopy, where the image intensity is modified by lens aberrations (spherical aberration and defocusing). The method for deconvolution is applied to computer-generated results subject to (i) random errors in the range ±20% and (ii) photographic noise in the range ±20%.

The disorder in the molecular array of a crystal lattice caused by a fission fragment has been studied by high-resolution electron microscopy. Disturbances in the (20ī) fringes of platinum phthalocyanine have been observed and a limited theoretical interpretation of these disturbances suggests that complex dislocation arrays are formed over an area which is easily determined. In particular there is evidence that dislocation dipoles can remain behind in a crystal after fission fragment bombardment. Molecular planes are shown to curve inwards towards the localized regions of damage. Observations made on the optical absorption spectra of copper and platinum phthalocyanine, both irradiated and unirradiated, are also described. The technique of irradiating thin crystals with fission fragments and observing the resultant damage in the electron microscope has been extended to other materials. In moiré patterns on overlapping crystals of molybdenum trioxide there is further evidence of a curvature of the molecular planes near regions of damage and in molybdenum disulphide dislocations resulting from irradiation are revealed by diffraction contrast. There is evidence that the radiation damage bothe crystal lattice can be due to both thermal and displacement spikes and their relative importance is dependent on the nature of the crystal.

Permanent magnets have been successfully utilized to energize magnetic lens pole pieces for high resolution electron microscopy at direct magnifications of 7000 times with 30‐kilovolt electrons, and 6000 times at 50 kilovolts. Stray magnetic fields, which have previously limited high magnification and high resolution, have been minimized by using two circuit gaps in parallel and by surrounding the assembly with a magnetic shield connected to the external pole pieces of the two gaps. Magnetomotive forces of 1400 gilberts have been obtained. A single magnet, magnets in bucking arrangement, and configurations involving magnets disposed either radially or parallel to the optical axis of the lens, have been successfully utilized. The effects of various magnetic circuit parameters on the design and operation of the lens system have been studied.

In recent years high resolution electron-microscopy has become a popular technique for studying point defect agglomerates produced in solids by irradiation or quenching (for a comprehensive review ...