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Platinum/iridium/carbon: a high‐resolutionshadowing materialfor TEM, STM and SEMof biologicalmacromolecularstructures Roger WepfMatthias AmreinUrs Bürkli1991 год

Platinum/iridium/carbon: a high‐resolution shadowing material for TEM, STM and SEM of biological macromolecular structures
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Аннотация: SUMMARY Thin Pt/Ir/C coating films (1.5 nm) show a fine granularity and provide a high structural resolution in the transmission electron microscope (TEM) when applied to freeze‐dried biological macromolecules. They keep their structure when exposed to atmospheric conditions, without the need of an additional stabilizing carbon layer, in contrast to conventional high‐resolution shadowing materials such as Ta/W and Pt/C. However, the correct ratio of the components has turned out to be crucial. When evaporating Pt/Ir/C from the source electrode in an electron‐beam‐heated evaporator, the ratio of the three elements changes progressively, and, consequently, the properties of such films depend strongly on the mass that has been pre‐evaporated. In this paper we present a quantitative analysis of the composition of Pt/Ir/C films by wavelength‐dispersive X‐ray analysis (WDX) undertaken in association with TEM experiments. We applied Pt/Ir/C shadowing to two regular biological test specimens, the phage T4 type III polyhead and the HPI‐layer of Deinococcus radiodurans. It turns out that Pt/Ir/C films containing at least 25% C are three‐dimensionally stable on the freeze‐dried macromolecular samples. By the dramatically improved resolution power of the latest scanning electron microscopes (SEM) and the invention of the scanning tunnelling microscope (STM), two new surface‐sensitive tools for the investigation of biological macromolecular structures became available. The Pt/Ir/C coating has proved to be well suited for STM and SEM imaging of freeze‐dried biological structures because of its good electrical conductivity and its direct three‐dimensional stability. We compare STM, SEM and TEM images of freeze‐dried and Pt/Ir/C‐coated polyheads.
Год издания: 1991
Авторы: Roger Wepf, Matthias Amrein, Urs Bürkli, Heinz Gross
Издательство: Wiley
Источник: Journal of Microscopy
Ключевые слова: Advanced Electron Microscopy Techniques and Applications, Force Microscopy Techniques and Applications, Molecular Junctions and Nanostructures
Другие ссылки: Journal of Microscopy (HTML)
PubMed (HTML)