Chain conformation complex

Perez et al. [128] investigated the crystal structure of 4-(4 -ethoxybezoy-loxy)-2-butoxy-4 -(4-butoxysalicylaldimine)azobenzene. This compound contains four rings in the main core and a lateral alkoxy branch on one of the inner rings. The lateral butoxy chain is nearly perpendicular to the long axis of the main core. This molecular conformation induces the molecules to make a very complex network in the solid. The crystal cohesion is due to van der Waals interactions. The change of the lateral chain conformation in the solid and nematic phases is discussed. 

Young, A.J., Phillip, D.M., and Hashimoto, H. 2002. Ring-to-chain conformation may be a determining factor in the ability of xanthophylls to bind to the bulk light-harvesting complex of plants. J. Mol. Struct. 642 137-145. 

Figure 11. Illustration of Equation 1 for the calculation of the increase in number of intermediate chain conformations accompanying deformation and activation of the polymeric catalyst-substrate complexes...

It is difficult to prepare stretched oriented fibres and such fibres may differ in their polymer chain conformation compared with the unstretched materials. Furthermore the quality of the single crystal X-ray data is poor and difficult to interpret. In contrast power X-ray data of relatively high quality may be obtained from polycrystalline polymer films. Lightfoot, Mehta and Bruce (1992) have obtained the first crystal structure of a polymer-salt complex, PEOjiNaClQ from powder X-ray data. Fig. 5.11(h). The structure is similar to the corresponding PEOjiNal structure, the PEO chains are wrapped around the Na ions with each Na ... 

Note 1 For a single-strand polymer molecule with skeletal bonds all joined by the same value of valence angle, the contour length is equal to the end-to-end distance of the chain extended to the all-trans conformation. For chains of complex structures, only approximate values of the contour length may be accessible. 

Removal of the solvent from the tri-O-ethylamylose-chloroform complex (TEA1-C2) results in a new polymorph (TEA3) of tri-O-ethylamylose. The unit cell is orthorhombic, with a = 1.536 nm, b = 1.218 nm, and c = 1.548 nm. The space group is P212121. The chain conformation is a 4(-0.387) helix. The C-6-0-6 bond is in the t position, with x(5) = 143.3°. The structural relationship between the various polymorphs was discussed. 

It was also found that the diluents added after the end-linking were more easily removed, possibly because they were less entangled with the network structure, and this could correspond to differences in diluent chain conformations. Such comparisons can thus provide valuable information on the arrangements and transport of chains as constrained within complex network structures [20]. 

The binding of metal ions to peptides and proteins is a consequence of these molecules containing a great number of potential donor atoms through both the peptide backbone and amino acid side chains. The complexes formed exist in a variety of conformations that are sensitive to the pH environment of the complex [2,3]. With at least 20 amino acid combinations available, some with coordinating side chains, which can be linked in any particular order and length, the number of ligands that... 

Structural studies of amylose have, in turn, revealed a wide range of crystalline polymorphy, both in chain conformation and in crystalline packing. An example is the group of V-amyloses that exist as complexes with small organic molecules, water, or iodine. The latter complex is particularly interesting because it displays an intense blue color. The V-amyloses can be prepared by precipitation or drying from solution, and they crystallize readily. Consequently, their crystal structures are of interest in connection with any regenerated form of starch material. 

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