Electron microscopy structure

Key words microporous materials, zeolites, electron microscopy, structure determination... 

Bernal, R. A., and Stock, D. (2004). Three-dimensional structure of the intact Thermus thermophilus 111 -ATPase/synthase by electron microscopy. Structure 12, 1789-1798. 

Jimenez JL, Guijarro JI, Orlova E, Zurdo J, Dobson CM, Sunde M, Saibil HR. Cryo-electron microscopy structure of an SH3 amyloid fibril and model of the molecular packing. EMBO J. 1999 18 815-821. 

The refined 4 A resolution electron microscopy structure of the hetero-pentameric musde-type, (al)2jSyd uAChR has elegantly illustrated considerable structural similarity of L-AChBP with the nAChR ligand-binding domain. Therefore, L-AChBP is now considered a structural and functional surrogate of the nAChRs. 

Katpally U, Voss NR, Cavazza T, Taube S, Rubin JR, Young VL, Stuckey J, Ward VK, Virgin HWT, Wobus CE et al. (2010) High-resolution cryo-electron microscopy structures of... 

Scanning Electron Microscopy Structure, porosity, mineral composition, geochemistry Little sampling damage Decay (weathering minerals and porosity), salts, stains... 

Transmission electron microscopy (TEM) can resolve features down to about 1 nm and allows the use of electron diffraction to characterize the structure. Since electrons must pass through the sample however, the technique is limited to thin films. One cryoelectron microscopic study of fatty-acid Langmuir films on vitrified water [13] showed faceted crystals. The application of TEM to Langmuir-Blodgett films is discussed in Chapter XV. 

With certain critical Pco/Poi ratios, structural oscillations can be observed [306]. Patterns of stationary and/or traveling waves can actually be seen by means of photoemission electron microscopy (see Ref. 313, and note Section XVIII-7B. Such behavior can be modeled mathematically (e.g.. Refs. 214, 314). 

Berriman J and Unwin N 1994 Analysis of transient structures by cryo-electron microscopy combined with rapid mixing of spray droplets Ultramicroscopy 56 241-52... 

For bulk structural detemiination (see chapter B 1.9). the main teclmique used has been x-ray diffraction (XRD). Several other teclmiques are also available for more specialized applications, including electron diffraction (ED) for thin film structures and gas-phase molecules neutron diffraction (ND) and nuclear magnetic resonance (NMR) for magnetic studies (see chapter B1.12 and chapter B1.13) x-ray absorption fine structure (XAFS) for local structures in small or unstable samples and other spectroscopies to examine local structures in molecules. Electron microscopy also plays an important role, primarily tlirough unaging (see chapter B1.17). 

A completely new method of determining siufaces arises from the enormous developments in electron microscopy. In contrast to the above-mentioned methods where the surfaces were calculated, molecular surfaces can be determined experimentally through new technologies such as electron cryomicroscopy [188]. Here, the molecular surface is limited by the resolution of the experimental instruments. Current methods can reach resolutions down to about 10 A, which allows the visualization of protein structures and secondary structure elements [189]. The advantage of this method is that it can be apphed to derive molecular structures of maaomolecules in the native state. 

A variety of experimental techniques have been employed to research the material of this chapter, many of which we shall not even mention. For example, pressure as well as temperature has been used as an experimental variable to study volume effects. Dielectric constants, indices of refraction, and nuclear magnetic resonsance (NMR) spectra are used, as well as mechanical relaxations, to monitor the onset of the glassy state. X-ray, electron, and neutron diffraction are used to elucidate structure along with electron microscopy. It would take us too far afield to trace all these different techniques and the results obtained from each, so we restrict ourselves to discussing only a few types of experimental data. Our failure to mention all sources of data does not imply that these other techniques have not been employed to good advantage in the study of the topics contained herein. 

This electron microscopy reconstruction has since been extended to high resolution (3 A) where the connections between the helices and the bound retinal molecule are visible together with the seven helices (Figure 12.3c). The helices are tilted by about 20° with respect to the plane of the membrane. This is the first example of a high-resolution three-dimensional protein structure determination using electron microscopy. The structure has subsequently been confirmed by x-ray crystallographic studies to 2 A resolution. 

The three-dimensional structure of the bacterial membrane protein, bac-teriorhodopsin, was the first to be obtained from electron microscopy of two-dimensional crystals. This method is now being successfully applied to several other membrane-bound proteins. 

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