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Structure Analysis and X-Ray Diffraction

The traditional bases of protein chemistry have been sequencing for primary structure analysis and x-ray diffraction and nuclear magnetic resonance (NMR) spectroscopy for three-dimensional structure determinations. It is clear that a complete understanding of biochemical processes and their regulation will depend on information at the atomic level. Historically, structure determination by x-ray diffraction and NMR, and the characterization of dynamic processes by NMR, have lagged behind the genetic and biochemical characterization of cellular processes. However, new advances in both of these methods promise to accelerate the rate of structure determination and to increase the size and complexity of systems that can be studied by magnetic resonance. [Pg.2]

The Sr-Cu system has been critically assessed. The most recent phase diagram, determined by combining differential thermal analysis and x-ray diffraction techniques, contains two intermediate compounds, both of which form in peritectic reactions, SrCu (588°C) and SrCu, (845°C) SrCu has also been prepared for independent structural analysis-. ... [Pg.443]

The term plastic crystal is not used if the rotation of the particles is hindered, i.e. if the molecules or ions perform rotational vibrations (librations) about their centers of gravity with large amplitudes this may include the occurrence of several preferred orientations. Instead, such crystals are said to have orientational disorder. Such crystals are annoying during crystal structure analysis by X-ray diffraction because the atoms can hardly be located. This situation is frequent among ions like BF4, PFg or N(CH3)J. To circumvent difficulties during structure determination, experienced chemists avoid such ions and prefer heavier, less symmetrical or more bulky ions. [Pg.27]

The physical environment within a crystal, of course, is not identical to that in solution or in a living cell. A crystal imposes a space and time average on the structure deduced from its analysis, and x-ray diffraction studies provide little information about molecular motion within the protein. The conformation of proteins in a crystal could in principle also be affected by nonphysiological factors such as incidental... [Pg.137]

The objectives in this chapter are to illustrate the various kinds of information that are immediately derivable from a crystal-structure analysis by X-ray diffraction and their applications to alkaloid molecules. From unequivocally providing the structural formula, stereochemistry, and absolute configuration of an alkaloid of unknown formula to establishing the spatial arrangement of the atoms, particularly the disposition of the atoms that are the reactive centers or that provide a steric hindrance to reaction, crystal-structure analyses are extremely useful and often indispensable. [Pg.81]

The polymers whose geometric structures have been quantitatively evaluated are polyacetylene 89), poly(ferf-butylacetylene)19), poly(isopropylacetylene)14), and poly-(phenylacetylene)88). In the case of polymers from aromatic monosubstituted acetylenes, qualitative evaluation of geometric structure is possible by means of IR spectroscopy, differential thermal analysis, and X-ray diffraction 66,90). In contrast, no information has been obtained on the geometric structure of disubstituted acetylene polymers. This is due to the fact that their main chain comprises fully substituted ethylene units, the difference between cis and trans structures being small. [Pg.146]

This paper describes the results of an experimental study of condensed phase equilibria in the system MoFe-UFo carried out by thermal analysis and x-ray diffraction analysis. A temperature-composition phase diagram is constructed from the temperatures of observed thermal arrests in MoFe-UFe mixtures, and the basis for the formation of this particular type of diagram is traced to the physical properties of the pure components. The solid-solubility relations indicated by the diagram are traced to the crystal structures of the pure solids. [Pg.309]

A. Kvick and J. H. Noordik, Acta Crystallogr., Sect. B, 33, 2862 (1977). Hydrogen Bond Studies. CXXl. Structure Determination of 2-Amino-4-methylpyridine by Molecular Packing Analysis and X-Ray Diffraction. [Pg.359]

Kory MJ, Worle M, Weber T, Payamyar P, van de Poll SW, Dshemuchadse J, Trapp N, Schliiter AD (2014) Gram-scale synthesis of two-dimensional polymer crystals and their structure analysis by X-ray diffraction. Nat Chem 6 779-784... [Pg.281]

A series of tests was therefore carried out including chemical analysis and X-ray diffraction of the combustion residues and metal structure microscopy of the floor liner. The corrosive thinning mechanism of the liner in the Monju accident and Sodium Leak Combustion Test-II were compared. An important aspect was the measurement of the moisture released from heated concrete, since the quantity of moisture determines the... [Pg.116]

Because passive films are extremely thin (1-3 nm), the usual techniques of chemical analysis and X-ray diffraction are not suited for determining their composition and structure. Furthermore, exposed to an electrolytic environment, the passive film is continually regenerating itself, with the dissolution rate of the film equal to the corrosion rate of the metal. Indeed, this capacity of self-regeneration is an important property of passive films. Despite their immense technological importance, our knowledge of the structure, composition and properties of passive films is therefore still limited. [Pg.240]


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X-ray diffraction and

X-ray structure analysis

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