Crystal structure three-dimensional

We now move on to defects that have some spacial extent, even if only in one dimension. As we continue to increase the geometric complexity of these defects, you may find it more difficult to visualize them. As with crystal structures, three-dimensional models may help you with visualization, and do not limit yourself to one representation of a specific defect—look for multiple views of the same thing. 

Figure 7.15. Rhodopsin crystal Structure. Three-dimensional structure of ihodopsin based on X-ray crystallography (186). Note that all-trans-retinal is protected fbm the intradiscal side by multiple structural elements, including several strands. Carbohydrates are in blue, 11 -cis-retinal is in green, and helices are in gray. Red shadows are added for esthetic reasons. This figure was generated by C. Behnke (UniversityofWashington)and is reprinted with permission from Prog. Retin, B/q Res., 20, 469-521 (2001).See color insert.

Liquid Crystalline Polymers. One class of polymers that requires some special attention from a structural standpoint is liquid crystalline polymers, or LCPs. Liquid crystalline polymers are nonisotropic materials that are composed of long molecules parallel to each other in large clusters and that have properties intermediate between those of crystalline solids and liquids. Because they are neither completely liquids nor solids, LCPs are called mesophase (intermediate phase) materials. These mesophase materials have liquid-like properties, so that they can flow but under certain conditions, they also have long-range order and crystal structures. Because they are liquid-like, LCPs have a translational degree of freedom that most solid crystals we have described so far do not have. That is, crystals have three-dimensional order, whereas LCPs have only one- or two-dimensional order. Nevertheless, they are called crystals, and we shall treat them as such in this section. 

Most recently, the TB MO theory for chemical shift calculation of polymer crystals with three dimensional structure within the ab initio framework has been developed and has been successfully applied to polyethylene crystals(42). 

Fontecilla-Camps, J.-C., Habersetzer-Rochat, C. and Rochat, H. (1988). Orthorhombic crystals and three-dimensional structure of the potent toxin II from the scorpion Androctonus australis Hector. Proc. Natl. Acad. Sci. USA, 85, 7443-7447. 

Maunsbach, A.B., Skriver, E., Hebert, H. (1991). Two-dimensional crystals and three-dimensional structure of Na,K-ATPase analyzed by electron microscopy. In The Sodium Pump Structure, Mechanism, and Regulation (Kaplan, J.H. De Weer, P., eds.), pp. 159-172, The Rockefeller University Press, New York. 

The entrapment-type nanocomposites can be prepared from zeolites and they are of two types zeolite-inorganic and zeolite-organic. Zeolite crystals are three-dimensionally linked network structures of aluminosilicate, aluminophosphate (ALPO), and silicoaluminophosphate (SAPO) composition and are porous, the pores being in the range of 2.8 to 10 A. Many of the highly siliceous, ALPO, and SAPO zeolites have been synthesized using organic templates such as tetrapropyl... 

Williams PA, Cosme JM, Matak-Vinkovic D, Williams MG, Jhoti H. Crystals and three-dimensional structures of human cytochrome P 450 2C9 and their use in ligand design and homology modeling. Ed. (Astex Technology Ltd. U. 2003-426058[2004053383], 806. 20040318. US. 30-4-2003. 

Cahill et al. have used variable temperature Li MAS NMR spectroscopy to study the lithium dynamics of monoclinic Li3V2(P04)3 [136]. The three lithium sites at 103, 52, and 17 ppm (labeled Li3, Li2, and Lil respectively) are clearly resolved and unambiguously assigned at a sample spinning speed of 25 kHz and a magnetic field strength of 7 T. The relative intensity of the peaks, including contributions from the respective side-band intensities was 1 1 1, as predicted from the crystal structure. One-dimensional Li MAS NMR spectra taken from 276 to 364 K (see Fig. 8.9) display a linear shift dependence with respect to temperature... 

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