Cryo-AFM

Currently, both AFM and STM are in their infancies regarding applications to plant systems. Thus, the future most likely will involve adapting these methods to plant investigations. Furthermore, it is anticipated that cryo-AFM will be more widely employed as investigators continue to improve AFM resolution. In this regard, the future of probe-based microscopies is discussed by Paesler and Moyer (41). 

Interesting observations have also been made by Shao and Zhang [31], who used cryo-AFM to investigate the effect of osmotic stress on the influenza virus, where the virus was first adsorbed onto mica, where excess particles were removed. The remaining surface particles were then immersed in deionised water, producing osmotic shock, which caused the capsid envelope to burst and release RNA. Here the rupture pore was also clearly visible, allowing the internal structure to be analysed. 

NR with standard recipe with 10 phr CB (NR 10) was prepared as the sample. The compound recipe is shown in Table 21.2. The sectioned surface by cryo-microtome was observed by AFM. The cantilever used in this smdy was made of Si3N4. The adhesion between probe tip and sample makes the situation complicated and it becomes impossible to apply mathematical analysis with the assumption of Hertzian contact in order to estimate Young s modulus from force-distance curve. Thus, aU the experiments were performed in distilled water. The selection of cantilever is another important factor to discuss the quantitative value of Young s modulus. The spring constant of 0.12 N m (nominal) was used, which was appropriate to deform at rubbery regions. The FV technique was employed as explained in Section 21.3.3. The maximum load was defined as the load corresponding to the set-point deflection. 

Figure 31-3 (A) Cryo atomic force (AFM) micrograph of molecules of the human immunoglobulin IgM. Courtesy of Zhifeng Shao, University of Virginia. (B) Schematic diagram. One-fifth of this structure is shown in greater detail in Fig. 31-4A. (C) Model based on earlier electron microscopic images. From Feinstein and Munn. 64(2...

Spherical micelles are not the only association structure that is formed by polyelectrolyte block copolymers. With increasing hydrophobic block length there is a tendency to form block copolymer vesicles. A vesicle formed by PB-P2VP.HC1 is shown in the cryo-TEM image in Fig. 14a. The bilayer structure is clearly resolved which shows that block copolymer vesicles are structurally very similar to lipid vesicles. Vesicles can be also imaged by AFM (Fig. 14b) where they exhibit a characteristic outer rim because the interior solution of the vesicle has evaporated during sample preparation leaving a shape that resembles that of an empty football. Vesicles typically have diameters of 100-300 nm and a bilayer thickness of 10-20 nm. 

Fig. 14 Cryo-TEM (a), AFM- (b), and TEM images of polyelectrolyte block copolymer vesicles (PB-P2VP.MeI). The image (c) is taken from a silica-template which was obtained by a sol/gel-process of a concentrated micellar solution [47, 56, 64]...

Currently, the resolution of AFM is lower than that of NMR, XRD, or cryo-EM. The highest resolution AFM data thus far has been collected on samples in 2-D crystals, producing structural data with resolutions between 9 and 14 A (77-80). In general terms, AFM works by raster scaiming (scaiming line by line) a very sharp tip attached to a flexible cantilever over a sample... 

Particulate filled EPDM mbber can be produced via conventional mixing procedures as described in [141]. Pure precipitated silica (Ultrasil VN3) and silica modified with a commerically available organosilane (Si 69), as well as carbon black (N 550) are employed as fillers.7 Unvulcanized samples for AFM observation are prepared by cutting small pieces of the compounds using a scalpel knife [(cryo)... 

Styrene, DVB, and styrene/ DVB CTAT/SDBS and others 3 1 Spontaneous V-50,60-65 °C Hollow polymer spheres QELS, Cryo TEM, SANS,AFM,GPC, stability tests Morgan et al. (1997) [11] McKelvey et al. (2000) [24]... 

STM and AFM are the most direct techniques for structural analysis because image generation does not involve substantial amounts of mathematical processing in order to obtain an image to view. Of these two techniques, AFM now holds the most utility for the visualisation of biological macromolecules and ambient temperatures and even in buffer conditions. Compared with X-ray crystallography, AFM is obviously also a technique still in development rather than fully mature, like cryo-electron microscopy. Nevertheless, we believe that it is necessary... 

Figure 12.2 Polypropylene TPO reactor powder morphology. AFM image of embedded and cryo-faced-off reactor powder particle.

Figure 12.6 Polypropylene TPO injection-molded bar (made from commercial pellets in Fig. 12.5) morphology. AFM image of cryo-faced-off section of core of injection-molded bar.

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