Backbone structural elucidation

Using 18 trNOE-derived distance restraints and 13 trCCR-derived backbone torsion angle restraints, structure calculations using distance geometry and simulated annealing [48] resulted in a well-defined structure of the IKK/1-derived peptide bound to NEMO. The backbone structure is displayed in Fig. 7B and is compared with the result of the calculation carried out using the trNOE-derived distance restraints alone. It is obvious from Eig. 7 that only the combination of the trNOE- and trCCR-derived restraints results in the structure elucidation of the bound conformation of this peptide. 

Chiral monodentate phosphites and phosphoramidites are also effective ligands for Rh-catalyzed asymmetric hydrogenation of enamide substrates. As seen in the structure of MonoPhos illustrated in Figure 1.2, combination of the mod-ihed BINOF backbone and the amine part gives a structural variety to this type of ligand. Combinatorial methods are effective for optimization of the chiral structures.Elucidation of the hydrogenation mechanism catalyzed by the MonoPhos-Rh complex is in progress." ... 

Structure elucidation of heteroatom-containing backbones in organoelement compounds... 

Molinaro, A., De Castro, C., Lanzetta, R., Parrilli, M., Raio, A., Zoina, A. Structural elucidation of a novel core oligosaccharide backbone of the lipopolysaccharide from the new bacterial species Agrobacterium larrymoorei. Carbohydr Res 338 (2003) 2721-2730. 

A further problem of N chemical shift calculations is the influence of electron correlation. In calculations on the Hartree-Fock level the error is typically 20 ppm for isotropic nitrogen values. The observed range of backbone nitrogen chemical shifts is also about 20 ppm, hence only calculations on the MP2 level or better are suitable for structure elucidation or it must be assumed that the correlation effects are constant within the pool of studied structures. 

The second important step in elucidation of mannoprotein structure was the discovery of an enzyme with the ability to remove the mannan sidechains selectively so that the backbone structure co ild be studied (12). As a consequence, several yeast mannans, although not all, have been shown to have a linear al -linked backbone (13> 1, 1 ). As a corollary, it follows that the acetolysis oligosaccharides represent sidechain fragments of the mannan, and by their characterization we were able to arrive at schematic structures for the mannan chains (Figure 2). 

H. Masoud, M. B. Perry, J.-R. Brisson, D. Uhri n, and J. C. Richards, Can.. Chem., 72,1466 (1994). Structural Elucidation of the Backbone Oligosaccharide from the Lipopolysac-charide of Moraxella catarrhalis Serotype A. 

Boyle CD, Harmange JC, Kishi YJ (1994) Novel Structure Elucidation of AAL Toxin TA Backbone. J Am Chem Soc 116 4995... 

The structural elucidation of polysaccharides represents an even greater challenge. The individual monosaccharide subunits that constitute the unknown polysaccharide must first be identified. Then the ring size and position in the polysaccharide sequence must be elucidated for each monosaccharide. Finally, the nature of the gly-cosidic linkages that form the polysaccharide backbone must be defined. Toward this end, it is necessary to establish which hydroxyl group on one monosaccharide is involved in the formation of the acetal or ketal that forms the glycosidic bond to the adjoining monosaccharide the stereochemistry at this anomeric center must also be determined. 

Hsu, F.F. and Turk, J. (2010) Electrospray ionization mnltiple-stage linear ion-trap mass spectrometry for structural elucidation of triacylglycerols Assignment of fatty acyl groups on the glycerol backbone and location of donble bonds. J. Am. Soc. Mass Spectrom. 21, 657-669. 

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