SINGLE-STRUCTURAL DOMAIN

The structural transition is directly monitored using X-ray diffraction (XRD) (see Fig. 1), by observing the disappearance and appearance of the characteristic peaks. The limits of this method are mainly from the small sample size of -100 microns from a solution of a few nanoliters, compressed between two diamonds of l-mm thickness. The small physical size of the nanocrystal produces Debye-Scherrer broadening of the diffraction peaks (Cullity 1956), and very concentrated samples are required (optical 

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Non-isomorphism. The hierarchical decompositions in each of the three domains of description may be non-isomorphic, meaning that there is not a one-to-one mapping between the decomposition structures. For example. Figure 2-2 shows the synthesis of two operators in the Behavioral Domain, an add operator and a subtract operator, with a single Structural Domain components, an arithmetic-logic unit that... 

Parraga, G., et al. Zinc-dependent structure of a single-finger domain of yeast ADRl. Science 241 1489-1492, 1988. 

ChEs possess the a/ 3-fold structure, which is shared with other esterases and non-catalytic proteins such as thyroglobulin, glutactin, neurotactin, gliotactin and neuroligins, all of these include a single ChE domain. Both ChEs are ellipsoidal molecules of 45-60-65 A3. Their structure consists of a central, highly twisted, 8-12-stranded (3-sheet, in which most strands are parallel, flanked on both sides by a-helices. Studies have indicated three major domains within the protein ... 

SNAREs is an acronym for soluble NSF acceptor protein receptors. They are a superfamily of small and mostly membrane-bound proteins that are distinguished by the presence of a conserved stretch of 60 amino acids referred to as a SNARE motif. With few exceptions, a single transmembrane domain is located adjacent to the SNARE motif at the C-terminal end. Many SNAREs possess in addition an independently folded N-terminal domain whose structures are more diverse. 

Another distinction between protein domains are continuous and discontinuous domains. A continuous domain has a consecutive region of peptide that folds up to form a single domain all the examples in Fig. 2 are continuous domains. Discontinuous domains are composed of non-consecutive regions of the peptide to form a single domain. It is not obvious that discontinuous domains, unlike continuous domains, can exist in isolation. From known structures it has been shown that slightly less than one third of structural domains are discontinuous (Jones et al., 1998). 

The structure showed that the three base-paired stems I, II, and III form type A-DNA helices and that the core contained the two conserved structural domains described in the previous paragraph. A single Me + ion was bound in close proximity to the pro-Rp oxygen of Ag s phosphate and the N7 position of GlO.l. The phosphodiester backbone of the DNA inhibitor strand was splayed... 

The three hammerhead constructs display nearly identical solvent-protected (folded) sites except that HHal and RNA 6 show an additional protected site at position 15.3. This is an important site since in the hammerhead crystal structures this site in stem III is approached by domain I, part of the catalytic pocket. The authors believe that a single structure gives rise to the observed pattern of hydroxyl radical protection of nucleotides since protection at individual nucleotides varies in the same manner with Mg + concen-... 

Structural domains of proteins are sometimes encoded by a single coding segment of DNA i.e., by a single exon in a split gene. Domains of this type may have served as evolutionarily mobile modules that have spread to new proteins and multiplied during evolution. For example, the immunoglobulin structural domain is found not only in antibodies but also in a variety of cell surface proteins.229 252... 

Figure 7-20 (A) Subunit assembly of two C3 catalytic trimers (green) and three R2 regulatory dimers around the periphery in aspartate carbamoyltransferase. After Krause et a/.109 Courtesy of William N. Lipscomb. The aspartate-and carbamoylphosphate-binding domains of the catalytic subunits are labeled Asp and CP, respectivley, while the zinc and allosteric domains of the regulatory subunits are labeled Alio and Zn, respectively. (B) Ribbon drawing of a single pair of regulatory (left) and catalytic (right) subunits with the structural domains labeled. MolScript drawing from Thomas et al.no...

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