Platinum shadowed replica

Platinum-shadowed replicas of freeze-fractured samples were prepared in a Denton Vacuum DFE-3 with a Denton DV-502 High-Vacuum Evaporator. An electron microscope Hitachi HU-11A with an optimum resolution of 7 A was used to observe and photograph the replicas. 

An alternative method is the freeze-etching technique [24, 25], which consists of producing platinum shadowed replicas of fractures created in rapidly frozen biological systems or lyotropic liquid crystals. The fracture orientation is somewhat haphazard, but occurs preferentially within the paraffinic level of the bilayers. These methods offer the possibility of viewing bilayers directly and preparing stereoviews. Beautiful pictures of liquid crystalline DNA, both cholesteric and hexagonal, have been obtained, but individual molecules are not easily resolved. However, the director distribution can be deduced from the images [26],... 

The adsorption kinetics can be followed by ellipsometric measurements and the morphology of the film can be characterized by TEM coupled to a carbon platinum shadowed replica and atomic force microscopy (AFM) [14, 37]. For molecular concentration under the CMC,... 

Figure 4.9 TEM micrographs recorded on a platinum shadowed replica prepared by FFET. (a) Sample prepared on 5 % dispersion of overbased calcium didodecylbenzene sulfonate in dodecane. Spherical nanoparticles of 10 nm diameter are easily visible, (b) Extractive replica prepared on the same dispersion. (c) X-ray analysis of the selected area (black circle) reveals the composition of the particles (Ca, S, O) corresponding to the sulfonate. The presence of Pt is due to the shadowing layer and copper to the copper support grid, (d) Radial distribution functions (from EXAFS studies) uncorrected from phase shifts obtained on caldte, and two OCABS dispersions in oil. The presence of a single peak corresponding to the first Ca-0 distance points out the amorphous structure of the mineral part of the OCABS particles...

Fig 1. Electron micrograph of a platinum/carbon replica prepared by the fast-freeze, deep-etch, rotary-shadow replica technique printed in reverse contrast. Cell walls of onion parenchyma have an elaborate structure with many thin fibres bridging between thicker cellulosic microfibrils. Scale bar represents 200nm. 

Figure 5. Replica of platinum shadowed, fractured, (010) hydrogen-bonded surface showing chain folded crystallites aligned with their molecular axis along the draw direction arrowed...

Ghadially EN, Lock CJL, Lalonde JMA, Ghadially R. Platinosomes produced in synovial membrane by platinum coordination complexes. Virchows Arch., B, Cell Pathol. 1981 35 123-131. Beretta GL, Righetti SC, Lombardi L, Zunino F, Perego P. Electron microscopy analysis of early localization of cisplatin in ovarian carcinoma cells. Ultrastruct. Pathol. 2002 26 331-334. Ruben GC. Ultrathin (Inm) vertically shadowed platinum-carbon replicas for imaging individual molecules in freeze-etched biological DNA and material science metal and plastic specimens. J. Electron. Microsc. Tech. 1989 13 335-354. 

Figure 10. Electron micrograph of a platinum shadowed carbon replica of a tin oxid film rubbed with 1 jum diamond paste (after reference [41], [42]).

Shadowed platinum Platinum carbon replica carbon replica preparation removing in solvent... 

The samples of BR-reconstituted vesicle (100 pg BR/1.5 mM lipid) were quick-frozen using the technique of Heuser [23], and fractured in a Balzers BAF 400D freeze-fracture apparatus (Balzers, Liechtenstein). The replicas were obtained by rotary shadowing with platinum/carbon of ca. 7 nm thick and carbon of ca. 25 nm, and then examined in a Philips CM200 Ultra Twin electron microscope at 200 kV. 

Because of the low penetrating power of electrons, specimens for examination in transmission have to be very thin, depending on the circumstances tens or hundreds of nanometres in thickness. Surface features on thick specimens can be examined by making a thin replica. A standard technique is to evaporate a thin film of carbon on to the surface of interest, to shadow it by depositing an even thinner layer of platinum at a different angle, and then to remove the deposited replica, for example, by dissolution of the original specimen. 

The removal of direct carbon replicas is dependent upon the polymer. Boiling xylene vapor was used to remove drawn PE from replicas [296] in work on drawn polymer morphology. Hobbs and Pratt [297] described a direct carbon replica method for replication of a PBT impact fracture surface by evaporation of platinum at 20° and PBT removal in hexafluor-oisopropanol (HFIP). Latex film coalescence in poly(vinyl acrylate) homopolymer and vinyl acrylic copolymer latexes was studied using direct replicas [298]. As the latex films have a low glass transition temperature, they were cooled by liquid nitrogen to about -150°C in the vacuum evaporator and shadowed with Pt/ Pd at 45° followed by deposition of a carbon support film at 90° to the specimen surface. The latex films were dissolved in methyl acetate/ methanol. TEM micrographs of the latex films show the difference between films aged for various times (Section 5.5.2). 

Carbon replicas [427] are formed by the evaporation of a thin layer of carbon in a vacuum evaporator. Metal shadowing, at an angle of 20 to 45° to the specimen surface is performed while the specimen is in the evaporator. The highest resolution direct replica material is carbon/platinum (C/Pt). After evap-... 

Fig> 6, Replica of same location as in Fig. 5 after etching shadowed with platinum under 5 from the left. Magnification 0000 X ... 

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