Structural hierarchy

The structure of biological macromolecules is hierarchical, with distinct levels of structural organization representing increased levels of complexity and are defined as 

Not all levels of structure are required or represented in all biomacromolecules. In general, all biomacromolecules require a level of structure up to and including second-ary/tertiary for biological function. It should be emphasized that a representation/visuali-zation of a molecule is only a model described by the atoms and the positions (coordinates) of the atoms in three-dimensional space. This model is correct only when it conforms to the experimentally observed properties and activities. 

Biomacromolecules, by C. Stan Tsai Copyright 2007 John Wiley Sons, Inc. 

Rgure 2.7 Crystalline blocks, arranged in lamellae-like structures and separated by amorphous defect layers in LDPE contrast enhancement of the amorphous defect layers due to the combined effect of chemical staining and electron irradiation [1] 

Linear PE (HDPE) without such defect layers and with large crystalline blocks forms longer crystalline lamellae (white), covered by the crystalline-amorphous interphase (dark) see Fig. 2.8. 

Size and shape of spherulites Interior structure of spherulites Arrangement of lamellae Structure of lamellae Crystal structure, orientation 

An overview of structural and morphological elements of semicrystalline polymers ranging from nanometers up to the millimeter scale is sketched in Fig. 2.12 using 

There are many modifications of lamellar and superlamellar structures in different polymers, for instance, the cross-hatched lamellae in a-iPP (see Fig. 2.2) or the so-called shish kebab structures in oriented PE and PP see Fig. 2.13. Such structures appear when highly oriented melts crystallize (in the form of a bundle of oriented, longer macromolecules, the shish, and smaller perpendicular lamellae of folded macromolecules, the kebabs ). A peculiar shape is formed by spiral lamellae in TPU (also see Fig. 4.95 in Section 4.5.3). 

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The Danish biochemist Kai Linderstrom-Lang coined the terms "primary," "secondary," and "tertiary" structure to emphasize the structural hierarchy in... 

Piechocka IK, Bacabac RG, Potters M et al (2010) Structural hierarchy governs fibrin gel mechanics. Biophys J 98 2281-2289... 

Organoclay materials with higher-order organization can also be prepared by template-directed methods involving self-assembled supramolecular structures. In this approach, preformed organic architectures in the form of tubes, fibers, hollow shells, gyroids, helicoids, and so on are transferred into hybrid materials exhibiting structural hierarchy, complex form and ordered mesoporosity [47-55]. For example,... 

Figure 11.4 The structural hierarchy in proteins, (a) A segment of primary structure (b) secondary structure illustrated as a segment of alpha helix (c) tertiary structure in which helices are interspersed with coils, and (d) quaternary structure. (Illustration, Irving Geis/Geis Archive Trust. Copyright Howard Hughes Medical Institute. Reproduced with permission.)...

Fig. 5,22. Schematic illustration of UHMWPE fiber s structural hierarchy. After Ward (1985).

Since the chain regularity is an attribute of a development of higher levels of structural hierarchy, namely crystalline domains, stereoisomerism affects greatly the morphology and, thus, the mechanical properties of semicrystalline thermoplastics. 

Eby, R. K. and Hawthorne, F. C. (1993). Structural relations in copper oxysalt minerals I. Structural hierarchy. Acta Cryst. B49, 28-56. 

When subject to mechanical suesses, how do semicrystalline polymers respond macroscopically and, consequently, on all the finer levels of structural hierarchy ... 

Web indexes such as Yahoo have two major advantages over undirected surfing. First, the structured hierarchy of topics makes it easy to find a particular topic or subtopic and then e.xplore its links. Second, Yahoo does not make an attempt to compile every possible link on the Internet (a task that is virtually impossible, given the size of the Web). Rather, sites are evaluated for usefulness and quality by Yahoo s indexers. This means that the... 

FIGURE 1-11 Structural hierarchy in the molecular organization of cells. In this plant cell, the nucleus is an organelle containing several types of supramolecular complexes, including chromosomes. Chro-... 

Each class of molecules has a similar structural hierarchy subunits of fixed structure are connected by bonds of limited flexibility to form macromolecules with three-dimensional structures determined by noncovalent interactions. These macromolecules then interact to form the supramolecular structures and organelles that allow a cell to carry out its many metabolic functions. Together, the molecules described in Part I are the stuff of life. We begin with water. 

Sasaki, N., and Odajima, S. (1996). Elongation mechanism of collagen fibrils and force-strain relations of tendon at each level of structural hierarchy. J. Biomech. 29, 1131-1136. 

The structural hierarchy of melt-crystallised polyethylene is schematically displayed in Fig. 8. Crystal thickness and its controlling factors are discussed in Sect. 2. It includes one phenomenologically resolved issue, the initial crys-... 

Substantially more work is done on the elucidation of properties of regenerated silk, compared to film materials in view of the difficulty to fabricate uniform films. From Table 3, it can be concluded that the mechanical properties of man-made silk materials are inferior to the natural ones. This can be attributed to the fact that the final properties are greatly affected by the structural hierarchies. Typically, the "artificial" materials do not contain the controllable microstructure and supramolecular structure that natural ones possess. 

Although helical structures dominate the structural hierarchies found in proteins, random chain structures similar to those found in natural rubber also are found in tissues. The most-studied random chain polymer found in vertebrate tissues is elastin. 

Figure 3.1. Levels of structural analysis of tissues. The levels of structural hierarchy of tissues include levels viewed by eye, light microscope, electron microscope, and atomic force microscope.

Figure 3.28. Diagram illustrating the structural hierarchy in tendon. Collagen molecules (left) form microfibrils (not shown) that make up collagen fibrils, fibers, fascicles, and tendon units.

Life is a structural hierarchy of functioning units that has acquired through evolution the ability to store and process the information necessary for its own reproduction. 

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