Structural order and disorder

Presser, J. McDonough, S. Yeon and Y. Gogotsi, Energy Environ. Sci., 

Patchkovskii and T. Heine, Phys. Rev. E Stat, Nonlinear, Soft Matter Phys., 2009, 80, 031603. 

Uribe-Romo, J. R. Hunt, H. Furukawa, C. Klock, M. O Keeffe and 

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When various possible coordination sites can accomodate different absorbing atoms, EXAFS is able to collect independent as well as overlapping informations by a multi edges study of the same material. Sect. 2.1 shows why addition and cross-checking of independent data is of the utmost interest, precisely to solve structural order and disorder problems beyond the first coordination sphere. 

A. Magneli, Structural order and disorder in oxides of transition metals of the titanium, vanadium, and chromium groups, in The Chemistry of Extended Defects in Non-Metallic Solids (L. Eyring and M. O Keeffe, eds.), pp. 148-162, North-Holland, Amsterdam (1970). 

Xanthan is reported to undergo a chiroptically detected temperature or salt-driven conformational change from an ordered conformation at high salt and low temperature to a disordered conformation either associated with lowering the salt concentration, or with increasing the temperature (2-5). The primary structure of xanthan has been known for about a decade (6,7), but different structures have been suggested both for the ordered and disordered conformation. Some workers (8-13) conclude that the ordered conformation is double-stranded or double-helix, whereas others (14-17) claim that a single stranded description can account for the observed data under... 

In this study we use electron microscopy (EM) to study xanthan strandedness and topology both in the ordered and disordered conformation. Correlation of data obtained from electron micrographs to physical properties of dilute aqueous solution on the same sample will be used to provide a working hypothesis of the solution configuration of xanthan. Electron micrographs obtained from xanthan of different origins will be compared to assess similarities and differences in secondary structure at the level of resolution in the used EM technique. 

To obtain statistically significant comparisons of ordered and disordered sequences, much larger datasets were needed. To this end, disordered regions of proteins or wholly disordered proteins were identified by literature searches to find examples with structural characterizations that employed one or more of the following methods (1) X-ray crystallography, where absence of coordinates indicates a region of disorder (2) nuclear magnetic resonance (NMR), where several different features of the NMR spectra have been used to identify disorder and (3) circular dichroism (CD) spectroscopy, where whole-protein disorder is identified by a random coil-type CD spectrum. 

The success of the initial PONDRs based on small databases of disordered protein motivated attempts to improve predictor accuracy. The main limitation for such attempts has been and continues to be the lack of low-noise structural data for both ordered and disordered protein, where noise means ordered regions misclassified as disordered and vice versa. 

Before discussing the ROA band signatures and general spectral characteristics of the disordered types of structure found in unfolded proteins, it is helpful to review the ROA band signatures of cc-helix and /1-sheet together with those of loops, turns, and side chains, as shown by folded proteins containing significant amounts of extended secondary structure in order to demonstrate that ROA is able to discriminate adequately between ordered and disordered polypeptide sequences. Typical... 

Most often, real 2D chromatograms exhibit a composite ordered and disordered characteristic, that is, a series of disordered spots are superimposed over ordered spot sequences. When the chromatogram is derived from a mixture of several chemical families, a superficial look at the 2D separation map may give the impression of randomness. In that case, the autocovariance function, however, can resolve and help identify the hidden structured nature of the map. 

Teeter, M. M. Order and disorder in water structure of crystalline proteins. Developments in Biological Standardization, Vol. 74, p. 63-72. Acting Editors Joan C. May - F. Brown. S. Karger AG, CH-4009 Basel (Switzerland), 1992... 

In the previous chapter we looked at some questions concerning solid intermetallic phases both terminal (that is solubility fields which include one of the components) and intermediate. Particularly we have seen, in several alloy systems, the formation in the solid state of intermetallic compounds or, more generally, intermetallic phases. A few general and introductory remarks about these phases have been presented by means of Figs. 2.2-2.4, in which structural schemes of ordered and disordered phases have been suggested. On the other hand we have seen that in binary (and multi-component) metal systems, several crystalline phases (terminal and intermediate, stable and also metastable) may occur. 

Principles and types of modular series have been summarized in a book by Ferraris et al. (2004). A hierarchical classification of structure has been introduced as well as the application of modularity to structure description and modelling. The order/disorder theory has been presented as fundamental to developing a systematic theory of polytypism, dealing with structures based on both ordered and disordered stacking of one or more layers. The structures of a great number of compounds (minerals, complex oxides, salts, etc.) have been described and discussed. 

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