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Biomedical subjects

R Guckenberger

Publications and source records attributed to R Guckenberger.

25 records · Page 2Linked to original sources
PubMed1990

Thickness determination of biological samples with a zeta-calibrated scanning tunneling microscope.

A single-tube scanning tunneling microscope has been zeta-calibrated by using atomic steps of crystalline gold and was used for measuring the thickness of two biological samples, metal-coated as well as uncoated. The hexagonal surface layer of the bacterium Deinococcus radiodurans with an open network-type structure shows thickness values that are strongly influenced by the substrate and the preparation method. In contrast, the thickness of the purple membrane of Halobacterium halobium with its densely packed less-corrugated structure exhibits very little variation in thickness in coated preparations and the values obtained are in good agreement with x-ray data.

Bacteriorhodopsins↗
PubMed1988

A scanning tunneling microscope (STM) for biological applications: design and performance.

The design of a scanning tunneling microscope (STM) for biological applications, operating at ambient pressure, is described. The STM is combined with an "auxiliary" light microscope to facilitate finding and identifying specimen areas of interest. The performance of the STM has been tested with evaporated gold films and with graphite. We have evaluated evaporated carbon and platinum/carbon films deposited on glass or mica to be used as specimen supports. First applications to biological material coated with a conducting film of platinum/carbon are described.

Bacteria↗
PubMed1988

Scanning tunnelling microscopy of biomacromolecules.

When imaging biomacromolecules with a STM, coating of specimens with a conductive layer is a convenient preparation method which provides a good rate of success. Utilizing evaporated platinum/carbon as a coating film we have investigated two biomacromolecules of very different appearance. The first of these is the HPI-layer, a natural two-dimensional protein crystal with a period of 18 nm, which is found on the surface of the bacterium Deinococcus radiodurans. The second specimen is type IV collagen which forms long triple-helical strands approx. 1.5 nm in diameter. The resulting STM pictures compare very well with electron microscopical images.

Bacterial Proteins↗
PubMed1986

Three-dimensional structure of the regular surface layer (HPI layer) of Deinococcus radiodurans.

The low-resolution structure of the regular surface layer of Deinococcus radiodurans has been determined from negatively stained specimens by three-dimensional electron microscopy. The layer has P6 symmetry, a lattice constant of 18 nm and a thickness of 6.5 nm. Three-dimensional reconstruction was performed by a hybrid real space/Fourier space approach that incorporates partial compensation of lattice distortions: The model obtained is discussed in the light of independent information about the surface structure of this layer, derived from metal shadowing and surface relief reconstruction. While agreement is quite satisfactory for the apparently more rigid inner surface, the outer surface shows severe flattening effects. The structure of the HPI layer is compared with other bacterial surface layers using a classification scheme that is outlined in the Appendix.

Bacteria↗
PubMed1985

Decoration and shadowing of freeze-etched catalase crystals.

Aqueous suspensions of catalase crystals were freeze-cleaved, deep-etched and either shadowed with Ta/W at 45 degrees or decorated with 0.1-0.9 nm thick deposits of Au and Pt at normal incidence. The electron micrographs of the decorated specimens were processed by correlation averaging and compared with a relief reconstruction obtained from shadowed specimens. Pronounced decoration was observed on the catalase crystals at temperatures between 130 and 180 K. Disregarding the difficulties in interpretation, the averages of 0.1-0.2 nm thick Au and Pt films reveal more structural detail than the relief reconstruction. Perfect shadowing provides information on surface topography and is relatively easy to comprehend; decoration renders variations in physico-chemical affinity visible. Problems of the interference of decoration and shadowing effects in the intuitive interpretation of freeze-etch replicas and in relief reconstruction are discussed as well as the disturbing effects of a non-ideal carbon backing. The perspectives of using decoration intentionally as a positive staining technique for the investigation of frozen-hydrated surfaces are evaluated and quality criteria are defined.

Animals↗