Conformational regularity

Moreover, these conformational regularities are important in the study of reaction mechanisms, including intramolecular migrations, rearrangements, and solvolyses of bicyclo[3.3.1]nonane systems (e.g., see references 60,250, and 251). 

Most fibrous proteins have regular extended structures representing a structural complexity intermediate between pure secondary and tertiary structures of globular proteins. This conformational regularity is derived from regularities in their amino acid sequences. Table 5.9 lists some of their structural elements. 

The assumption that the 1126 cm absorption band is characteristic of the three-dimensional order or conformational regularity of the crystal phase and not associated with perfectly elongated individual chains only, is supported by orientation measurements at elevated ten >erature Thus, despite a drastic reduction strain-induced... 

The process of solification proceeds with the formation (when possible) of crystalline material in which chains pack in a lattice with tri-dimensional periodicity. The conditions for perfect packing are that chains possess chemical regularity, configurational periodicity, and conformational regularity. 

In reality, polymeric materials never possess the perfect chemical stereochemical and conformational regularity which were assumed at the beginning of Section 3.5. 

The monosaccharide structural unit conformation and the positions and types of linkages in the chain determine the chain conformation of a polysaccharide. In addition to irregular conformations, regular conformations are known which reflect the presence of at least a partial periodic sequence in the chain. Some typical conformations will be explained in the following discussion, with examples of glucans and some other polysaccharides. 

The crystalline state of a polymer is chararterized by a regular arrangement of conformationally regular polymer chains. Thus, conformational regularity (or one-dimensional (ID) crystallinity) is a necessary condition for the crystalline order of a polymer. For every crystalline polymer, there must exist a crystallographic unit cell whose translations in the three directions of its edges produce the macroscopic solid. 

Many polymers with long methylene sequences show in the low-frequency range of their Raman spectra bands whose wave-number positions depend on the length of these conformationally regular sequences. Earlier it was reported ... 

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