Structural hierarchy primary

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

Figure 1.3 Folding of a polypeptide chain illustrating the hierarchy of protein structure from primary structure through secondary structure and tertiary structure.

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.)...

Certain properties, common to all types of macromolecule, can be derived from such analyses. All seem to have a certain individuality and many have the ability to specifically recognize and interact with other substances. They are all, to a greater or lesser extent, flexible molecules, capable of adapting their shape in response to their particular microenvironment within the cell. They ail have a pronounced intolerance to extreme conditions, a fragility that makes them fall apart if treated harshly. Finally they all may be described in terms of a structural hierarchy of primary, secondary and tertiary structures that we need to look at in a little more detail. 

Figure 15.22 The structural hierarchy of proteins. A typical protein s structure can be viewed at different levels. Primary structure (shown as a long string of balls leaving and returning to the picture frame) is the sequence of amino acids. Secondary structure consists of highly ordered regions that occur as an a-helix or a p-sheet. Tertiary structure combines these ordered regions with more random sections. In many proteins, several tertiary units interact to give the quaternary structure.

Proteins often display substantial similarity in sequence and 3D stmcture, since many are derived from a basic complement of autonomously folding units (domains). This allows us to group proteins into a hierarchy of families, superfamilies and folds. Domains within protein structures are defined as spatially distinct structures that could conceivably fold and function in isolation. The concept of fold thus allows grouping of related structures for descriptive purposes and simplifies problems related to (he encoding of structure in primary sequences. 

A description of the protein-structure hierarchy is incomplete without a discussion of structural motifs, which are critical to an understanding of protein structure [17]. Identification of recurring motifs in protein structures has refined our knowledge of the protein-structure hierarchy these motifs occur at all levels from primary to tertiary. The Phe-Asp-Thr-Gly-Ser sequence found in the active site of all aspartic acid proteinases, and the Gly-Gly-X-Leu sequence (where X represents any amino acid residue) that predicts a 3-strand for the last two residues [17], are examples of sequence motifs a-helices, P-strands, and turns are examples of secondary-structural motifs PaP and PxP units, P-hairpins, and Greek keys are examples of supersecondary-structural motifs and four-a-helix bundles and TIM barrels are examples of tertiary-structural motifs. The tertiary fold of a protein is characterized by its tertiary-structural motif. 

There are several structural tiers that exist in a folded protein, sometimes referred to as the hierarchy of protein structure. Although different types of proteins can fold in very different ways, this structural hierarchy can be applied generally to all proteins primary, secondary, tertiary, and quaternary structure. 

Figure 13 The structural hierarchy of polysoaps involves three levels. The primary structure, the monomer sequence, is set hy the chemistry (a). The intrachain micelles introduce a secondary structure (b). The configurations of the micellar string, linear (c), branched (d), or globular (e), define the tertiary structure. (Adapted from Refs. 45 and 66.)...

Failure Mode and Effect Analysis (FMEA) is intended to identify failures which have significant consequences affecting the system performance in the application considered [1]. FMEA assumes that the system structure has been identified down to the level where the primary failure modes are avail le. From this level, FMEA determines secondary failure modes which may occur on the higher levels of the structure hierarchy. FMEA can be applied in a limited way during conception, planning and definition phases and more fully in the design and development... 

Fig. 3.2 Structural hierarchy of heteropoly compounds (a) Keggin cluster (primary particle), (b) secondary structure and (c) tertiary structure (texture particle size, porosity, surface area, etc.) (Adapted with permission fiorn Ref. [16]. Copyright 2001, Royal Society of Chemistry)...

DNA—as well as to history or species time, which is DNA s phylogenetic expression. To do this, we have chosen to treat the simple wave (fig. 18B), which is itself a composite expression of the entire / Ching, as a primary unit in a hierarchy in which every level is structured on the same principles as are the levels above and below it. This is termed a modular hierarchy ... 

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