Contrast in the electron spectroscopic imaging mode of a TEM

Reimer, Ludwig; Rennekamp, R.; Fromm, I.; Langenfeld, M.

doi:10.1111/j.1365-2818.1991.tb03111.x

Cited by 28 publications

(13 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…squares of the orbital coefficients) and the expected transitions, the imaginary part of the negative reciprocal dielectric function [Im(-l/~)] can be calculated. The cross-section of the excitation of electrons in the low-loss region is assumed to be proportional to the function Im(-1/~) (Daniels et al 1970;Reimer et al 1993). The obtained maxima in the Im(-1/~) function are compared with the measured spectrum in the low-loss region.…”

Section: Energy-dispersive Analysismentioning

confidence: 99%

Heat-shock proteins induce heavy-metal tolerance in higher plants

Neumann

Lichtenberger

Günther

et al. 1994

Planta

167

View full text Add to dashboard Cite

Abstract. Cell cultures of Lycopersicon peruvianum L.stressed with CdSO 4 (10-3M) show typical changes in the ultrastructure, starting with the plasmalemma and later on extending to the endoplasmic reticulum and the mitochondrial envelope. Part of the membrane material is extruded, with the formation of osmiophilic droplets which increase in size and number during the stress period. After 4 h, about 20% of the cells are dead. A short heat stress preceeding the heavy-metal stress induces a tolerance effect by preventing the membrane damage. The cells show a normal ultrastructure with one exception: cytoplasmic heat-shock granules are formed. This protective effect can be abolished by cycloheximide. Cadmium uptake is not markedly influenced by the heat stress. Cadmium is found together with sulfur in small deposits in the vacuoles of stressed cells. The precipitates contain an excess of sulfur, evidently due to the stress-induced formation of phytochelatins. The role in heavy-metal tolerance of heat-shock proteins in the plasmalemma (HSP70) and in cytoplasmic heat-stress granules (HSP17, HSP70) is discussed.

show abstract

Section: Energy-dispersive Analysismentioning

confidence: 99%

Heat-shock proteins induce heavy-metal tolerance in higher plants

Neumann

Lichtenberger

Günther

et al. 1994

Planta

167

View full text Add to dashboard Cite

show abstract

“…This is because the incident electrons undergo multiple inelastic scattering events producing a range of energy losses, so that the transmitted electrons are focused at different imaging planes due to chromatic aberration of the objective lens [11-12]. One way to circumvent this problem is to utilize only electrons with a narrow energy window (e.g.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo electron-trajectory simulations in bright-field and dark-field STEM: Implications for tomography of thick biological sections

et al. 2009

View full text Add to dashboard Cite

A Monte Carlo electron-trajectory calculation has been implemented to assess the optimal detector configuration for scanning transmission electron microscopy (STEM) tomography of thick biological sections. By modeling specimens containing 2 and 3 atomic % osmium in a carbon matrix, it was found that for 1-μm thick samples the bright-field (BF) and annular dark-field (ADF) signals give similar contrast and signal-to-noise ratio provided the ADF inner angle and BF outer angle are chosen optimally. Spatial resolution in STEM imaging of thick sections is compromised by multiple elastic scattering which results in a spread of scattering angles and thus a spread in lateral distances of the electrons leaving the bottom surface. However, the simulations reveal that a large fraction of these multiply scattered electrons are excluded from the BF detector, which results in higher spatial resolution in BF than in high-angle ADF images for objects situated towards the bottom of the sample. The calculations imply that STEM electron tomography of thick sections should be performed using a BF rather than an ADF detector. This advantage was verified by recording simultaneous BF and high-angle ADF-STEM tomographic tilt series from a stained 600-nm thick section of C. elegans. It was found that loss of spatial resolution occurred markedly at the bottom surface of the specimen in the ADF-STEM but significantly less in the BF-STEM tomographic reconstruction. Our results indicate that it might be feasible to use BF-STEM tomography to determine the 3D structure of whole eukaryotic microorganisms prepared by freeze-substitution, embedding, and sectioning.

show abstract

“…The mechanism of image formation for thick biological specimens has been previously investigated by a number of authors (Colliex et al, 1989;Reimer et al, 1991;Langmore & Smith, 1992). It is generally assumed that the main contrast mechanism for these specimens is so called amplitude or absorption contrast.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of image formation for thick biological specimens: exit wavefront reconstruction and electron energy‐loss spectroscopic imaging

Han

Sedat

Agard

1995

Journal of Microscopy

View full text Add to dashboard Cite

SUMMARY With increasing frequency, cellular organelles and nuclear structures are being investigated at high resolution using electron microscopic tomography of thick sections (0·3–1·0 μm). In order to reconstruct the structures in three dimensions accurately from the observed image intensities, it is essential to understand the relationship between the image intensity and the specimen mass density. The imaging of thick specimens is complicated by the large fraction of multiple scattering which gives rise to incoherent and partially coherent image components. Here we investigate the mechanism of image formation for thick biological specimens at 200 and 300 keV in order to resolve the coherent scattering component from the incoherent (multiple scattering) components. Two techniques were used: electron energy‐loss spectroscopic imaging (ESI) and exit wavefront reconstruction using a through‐focus series. Although it is commonly assumed that image formation of thick specimens is dominated by amplitude (absorption) contrast, we have found that for conventionally stained biological specimens phase contrast contributes significantly, and that at resolutions better than ∼10 nm, superposed phase contrast dominates. It is shown that the decrease in coherent scattering with specimen thickness is directly related to the increase in multiple scattering. It is further shown that exit wavefront reconstruction can exclude the microscope aberrations as well as the multiple scattering component from the image formation. Since most of the inelastic scattering with these thick specimens is actually multiple inelastic scattering, it is demonstrated that exit wavefront reconstruction can act as a partial energy filter. By virtue of excluding the multiple scattering, the ‘restored’ images display enhanced contrast and resolution. These findings have direct implications for the three‐dimensional reconstruction of thick biological specimens, where a simple direct relationship between image intensity and mass density was assumed, and the aberrations were left uncorrected.

show abstract

Contrast in the electron spectroscopic imaging mode of a TEM

Cited by 28 publications

References 20 publications

Heat-shock proteins induce heavy-metal tolerance in higher plants

Heat-shock proteins induce heavy-metal tolerance in higher plants

Monte Carlo electron-trajectory simulations in bright-field and dark-field STEM: Implications for tomography of thick biological sections

Mechanism of image formation for thick biological specimens: exit wavefront reconstruction and electron energy‐loss spectroscopic imaging

Contact Info

Product

Resources

About