Structures crystallization and

The crystallization and structural determination of the histone octamer was first reported in 1984 [34], However, the overall dimensions of the 3.3 A structure [15] did not appear to fit within the known X-ray structures of the nucleosome core particle [12,13], In an elegant analysis [16], re-examination of the original phasing of the histone octamer data revealed misplacement of the heavy atom site by 2.7 A. The structure was resolved, after which it was possible to build molecular models of the individual histones into the 3.1 A resolution electron density map of the histone core of the nucleosome [17]. Figure 2 shows the first atomic resolution model of the core histone octamer. Several additional publications followed in which the histone octamer structure formed the basis for constructing models of the NCP [17-21],... 

While most superoxo complexes—in contrast to peroxo compounds— have been assigned a bent, end-on coordination mode [9], the superoxide ligand of Tp Cr(02)Ph was suggested to exhibit the more unusual side-on (r] ) coordination [10]. The reactivity of the complex did not allow for the determination of its molecular structure however, close analogs could be isolated, crystallized and structurally characterized by X-ray diffraction. For example, the reaction of [Tp Cr(pz H)]BARF (pz H = 3-tert-butyl-5-methylpyrazole, BARF = tetrakis(3,5-bis(trifiuoromethyl)phenyl)borate) with O2 produced the stable dioxygen complex [Tp Cr(pz H)( ] -02)]BARF (Scheme 3, bottom), which featured a side-on bound superoxide ligand (do-o = 1.327(5) A, vo-o = 1072 cm ) [11]. Other structurally characterized... 

The switch fimction of the a-subunit of the heterotrimeric G-proteins is foimded on the change between an active G -GTP confirmation and an inactive Ga-GDP conformation. The structural difference between the two conformations was explained for the transducin, G, , by crystallization and structural characterization of the inactive GDP form and the active GTPyS form (Lambright et al., 1994). The structures of both forms of Gt, are shown in Fig. 5.19. 

The successful crystallization and structural determination of the constitutively open charmel of Streptomyces lividans (Doyle et al., 1998) represented a large step forward in the understanding of function and selectivity of ion channels. 

Temperature is the main factor that affects sintering and solid-state transformation experimental observations, however, have shown that the nature of the atmosphere in which the catalyst is heated may also play a part to an extent in the sintering process. For example, the presence of water vapor accelerates crystallization and structure modifications in oxide supports (Forzatti and Lietti, 1999). 

Tables II and III are presented as an initial attempt to establish a broad correlation between crystallization and structure in terms of cation composition. The extensive assumptions and uncertainties involved are well recognized including acceptance of assignment of framework type based on similarity of x-ray powder diffraction patterns, exclusion of some polyhedral cages found in zeolite structures (62) f the relative concentrations of cations in mixtures, variables other than cation, and the possible presence of impurity cations not reported but derived from reagents or reaction vessels.

Our understanding of synthase reactions and the types of the active sites involved in these reactions was advanced substantially by the crystallization and structural solution of tyrosyl-tRNA synthase complexed with the reaction intermediate tyrosyl-adenylate (fig. 29.10). The reaction intermediate is bound in a deep cleft in the enzyme and interacts with it through 11 hydrogen bonds. Six of these bonds are with the AMP moiety, and five are with the tyrosyl moiety of the intermediate. The amino acid selectivity of tyrosyl-tRNA synthase is thus determined primarily by the formation of specific hydrogen bonds with the amino acid. 

ECR-1 has a complex crystallization and structural relation-ship with mazzite and mordenite, and this paper should be viewed as a progress report from an ongoing project. The problems are symptomatic of a number of recent studies of zeolites showing high degrees of structural complexity, such as ZSM-23 (liL), beta(12) and various FAU-BSS intergrown materials (IS.). ... 

There are a number of significant motivations driving the development of molecular mechanics models of lanthanoid and actinoid complexes which, being relatively unstable, are notoriously difficult to crystallize and structurally characterize. At the same time there is strong interest in these structures. For example, lantha-... 

Kumaraswamy G, Verma RK and Kornfield JA (1999) Novel flow apparatus for investigating shear-enhanced crystallization and structure development in semicrystalline polymers. Rev Sci Instrum 70 2097-104. 

Nather, C., Bock, H. and Claridge, R. F. C. (1996a). Solvent-shared radical ion pairs [pyrene Na+0(C2H5)2] ESR evidence for two different aggregates in solution, room temperature crystallization, and structural proof of another polymorphic modification. Helv. Chim. Acta, 79, 84-91. [69]... 

Vedadi M, Niesen PH, Allali-Hassani A, Pedorov OY, Pinerty PI Ir, Wasney GA, Yeung R, Arrowsmith C, Ball LI, Berglund H, et al. Chemical screening methods to identify ligands that promote protein stability, protein crystallization, and structure determination. Proc. Natl. Acad. Sci. U.S.A. 2006 103 15835-15840. 

To date, the crystal structures of 12 different MMPs have been solved. Full structures were obtained for MMP-1 (2CLT), MMP-2 (1CK7), and MMP-7 (IMMP). As for the rest, only the catalytic domains in the presence of different inhibitors were determined. The hemopexin-like domains of MMP-2 (IRTG), MMP-9 (IITV), and MMP-13 (IPEX) were crystallized, and structures were determined separately. Nuclear magnetic resonance (NMR) structures of the catalytic domains of MMP-1 (1AYK), MMP-2 (IHOV), MMP-3 (lUMS), MMP-12 (1YCM), and MMP-13 (lEUB) have also become available. 

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