Spontaneous vesicles formed from hydroxide surfactants: evidence from electron microscopy

Dialkyldimethylammonium hydroxide surfactants are highly soluble in water and form spontaneous stable vesicles. These vesicles can be grown to size with added acid, and appear to provide an ideal membrane mimetic system for the study of fusion and ion transport. These phenomena are a consequence of strong hydration forces that are not necessarily limited to the hydroxide ions. The forces can be used to design a variety of model systems whose behavior differs from that of systems in which double-chained surfactants form insoluble liquid crystalline phases in water and unstable vesicle suspensions on prolonged sonication.     

Crustacean eye fine structure seen with scanning electron microscopy

The internal fine structure of crustacean compound eyes has been reexamined with scanning electron microscopy. Several different preparative techniques were used in a comparative study of crab, crayfish, shrimp, and stomatopod eyes. The three-dimensional pattern of photoreceptive, dioptric, and screening components of these eyes has been directly demonstrated, and new insight has been gained into their functional organization. Particularly interesting in apposition eyes is the elaborate array of boundary membranes and protoplasmic strands linking the photoreceptive microvilli to their parent cell cytoplasm across the large intracellular vacuoles surrounding the axial rhabdom. Quantitative application of scanning electron microscopy to this system promises to advance our understanding of its proven high rate of receptor membrane turnover.     

Transmission electron microscopy: direct observation of crystal structure in refractory ceramics

Using high-resolution multibeam interference techniques in the transmission electron microscope, images have been obtained that make possible a real-space structure analysis of a beryllium-silicon-nitrogen compound. The results illustrate the usefulness of lattice imaging in the analysis of local crystal structure in these technologically promising ceramic materials.     

Actomyosin from Physarum polycephalum: electron microscopy of myosin-enriched preparations

Negatively stained slime mold actomyosin examined by electron microscopy consists mainly of actin-like filaments with occasional angular projections. If some of the actin is removed, the myosin-enriched actomyosin appears as continuous arrowhead structures similar to those of vertebrate striated muscle actomyosin. Together with other evidence, the findings suggest that cytoplasmic streaming in Physarum may involve a contractile process operating at a relatively low myosin-actin ratio.     

Molecular structure of DNA by scanning tunneling microscopy

Uncoated DNA molecules marked with an activated tris(l-aziridinyl) phosphine oxide (TAPO) solution were deposited on gold substrates and imaged in air with the use of a high-resolution scanning tunneling microscope (STM). Constant-current and gap-modulated STM images show clear evidence of the helicity of the DNA structure: pitch periodicity ranges from 25 to 35 angstroms, whereas the average diameter is 20 angstroms. Molecular structure within a single helix turn was also observed.     

Virions from progressive multifocal leukoencephalopathy: rapid serological identification by electron microscopy

Virions were extracted directly from the brain of a patient with progressive multifocal leukoencephalopathy (PML). They were treated with antiserum to SV40, with rabbit antiserum to previous PML isolates, or with serum from another patient with the same disease and observed directly by electron microscopy. This procedure could be used for the rapid identification of the antigenic nature of virions in cases of PML.     

Subliming ice surfaces: freeze-etch electron microscopy

Vacuum sublimation of oriented single crystals of ice at temperatures from -110 to -60 degrees Celsius was studied by electron microscopy with the freeze-etch technique. Sublimation etches the ice surface to produce pits and asperities and above -85 degrees Celsius causes extreme surface roughening. The etch pits are ascribed to surface dislocations, and the extreme roughening is ascribed to the departure from unity of the vaporization coefficient. The asperities could not be attributed to impurities; they may be related to the whiskers that others have observed at higher temperatures.     

High-resolution electron microscopy of muscovite

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.     

Mapping of deletions and substitutions in heteroduplex DNA molecules of bacteriophage lambda by electron microscopy

Electron microscopy of heteroduplex DNA molecules, composed of one strand of Escherichia coli phage lambda(+) DNA annealed to the complementary DNA strand of a lambda deletion or substitution mutant, permits visualization, as well as precise measurements and mapping, of the unpaired single-stranded regions of nonhomology in the otherwise double-stranded molecules. In the lambdab2 mutant, the central segment (13 percent) of the lambda(+) DNA molecule is shown to be deleted. In the hybrid phages lambda(i434) and lambda(i21) a segment of the right arm of the lambda(+) genome (5.5 or 7.6 to 9 percent) is replaced by the corresponding immunity regions of phage 434 (3.3 percent or phage 21 (4 percent) DNA. The b5 region in the lambdab5 mutant appears to be identical to the i(21) segment. From these data it is possible to estimate the size and posiion of those lambda genes which are replaced by the i(434) and i(21) segments. The method permits preparing complete physical maps of viral genomes with a precision heretofore unattainable.     

Ballistic electron microscopy of individual molecules

We analyzed the transport of ballistic electrons through organic molecules on uniformly flat surfaces of bismuth grown on silicon. For the fullerene C60 and for a planar organic molecule (3,4,9,10-perylene-tetracarboxylic acid dianhydride), the signals revealed characteristic submolecular patterns that indicated where ballistic transport was enhanced or attenuated. The transport was associated to specific electronic molecular states. At electron energies of a few electron volts, this "scanning near-field electron transmission microscopy" method could be applied to various adsorbates or thin layers.     

Scanning electron microscopy of evaporating ice

Direct observation of evaporating ice with a scanning electron microscope indicates that the surfaces of single-crystal and polycrystalline ice are markedly different. In specimens of single-crystal ice the crystal planes are revealed by evaporation, whereas polycrystalline ice develops a fibrous surface.     

昆虫材料扫描电镜样品制备技术

在昆虫材料的扫描电镜样品制备中,组织固定是极其重要的环节.由于昆虫体壁均有一定程度的骨化,具有阻止外界物质侵入的作用,使得固定液不容易浸透昆虫体内组织器官,且昆虫体内液体含量较高,因此利用常规前固定方法（即用2％～3％的戊二醛固定）难以保持昆虫材料的原有形态.本研究通过改变固定液的配制方法,即在3％戊二醛中加入氯化钠及吐温-80,比较了桃蛀螟幼虫经过微波固定、常规固定和自然干燥标本处理后,在扫描电镜下的观察效果.结果发现：在微波和固定液共同处理下,昆虫材料扫描电镜样品皱缩程度显著降低,有益于观察昆虫体表的超微结构.研究结果可为昆虫扫描电镜材料的制备提供技术参考.     

Stereoscan electron microscopy of soil microorganisms

Details of the surface structure of microorganisms growing in soil and the complex topography of individual soil particles were observed with the Stereoscan electron microscope. Because it was not necessary to remove the microorganisms from the soil particles, it was possible to establish their occurrence in different microhabitats. This technique can provide useful ecological information about the soil microflora.     

Image-formation technique for scanning electron microscopy and electron probe microanalysis

A technique is described for topographic images on the scanning electron microscope and the scanning electron probe microanalyzer. In this technique, the brightness of the oscilloscope is modulated by a signal obtained by mixing the signal (from secondary electrons or targets current) with its first derivative. This enhances minor topographic features which are poorly reproduced in the technique.     

Viral RNA polymerases: electron microscopy of reovirus reaction cores

The Kleinschmidt technique has been used to observe reovirus cores that have synthesized messenger RNA. Some individual viral cores probably synthesize all ten messenger RNA molecules in vitro. Each messenger RNA molecule appears to be attached to a different site on the core surface, implying that there are probably a number of different enzymic sites in each core.     

Kinetics of single-layer graphite oxidation: evaluation by electron microscopy

Etch-decoration reveals that the rate of removal of carbon atoms exposed at monolayer steps on graphite surfaces is very different from the rate of removal, under identical conditions, at multilayer steps. At 1113 degrees K and a pressure of 1.33 newtons per square meter of oxygen, the rate of oxidation (along the layer planes) is less by a factor of nearly 100 than that at multilayer steps.