Carbohydrates chemical structure

F.a.b.-m.s. is a powerful technique for examining mixtures of carbohydrates. Many examples of such analyses are given in Sections V and VI. Unless the components have very different chemical structures, all will give molecular ions. However, the relative abundance of the ions will not necessarily reflect the relative concentrations of the components. Furthermore, if more than one class of carbohydrate is present, different pseudomolecular ions may be produced for each class. An example of such a phenomenon is given in Fig. 4. 

IWo chapters treat widely divergent aspects of the aqueous degradation of carbohydrates. Christopher J. Biermann (Corvallis) discusses aqueous acidic hydrolysis and other cleavages of glycosidic linkages in oligo- and polysaccharides, with specific emphasis on their relation to procedures for determination of chemical structure. In the final chapter, Olof Theander (Uppsala) and David A. Nelson (Richland) provide an informative treatment of the... 

It is difficult to reconcile the unique chemical structure of tetrodotoxin with that of an animal product. Its structure is not related to that of other animal products by any readily recognized biosynthetic scheme. It is not a terpenoid, not obviously formed from amino acid or carbohydrate units, and apparently not constructed from acetate or propionate units. Nor does it resemble any of the various plant alkaloid patterns. It thus appears to be a very unlikely animal product to result from known biogenetic pathways. In this connection the metabolic incorporation of radioactive precursors using torosa and ]C. granulosa salamanders was studied by Shimizu et al. (47). They observed significant isotopic incorporation into amino acids and steroid metabolites, but they found no such incorporation associated with tetrodotoxin. 

The parent CDs are cyclic carbohydrates consisting of a variable number of glucopy-ranose units linked by 1,4-glycosidic bonds. The chemical structure of fi-CD (Fig. 1) shows the cyclic nature and the three hydroxyl groups on each glucopyranose unit. Two of the hydroxyls are secondary alcohols and are located at the C2 and C3 positions of the glucopyranose unit. The third hydroxyl is a primary alcohol at the C6 position. 

Although studies on potato structure had been carried out previously using conventional SEM, van Marie et al [70] used cryo-SEM to advantage in this high moisture material. The fracture planes of cooked and uncooked samples were used to help characterize cell wall adhesion in the four potato cultivars. In particular, differences in cell wall contact area and surface detail were used to explain the mealy versus firm textural attributes in the cultivars. By determining the parameters which contributed to the texture of potatoes, processing conditions and selection of suitable raw materials could be facilitated. Such information would be difficult to obtain with conventional, chemically fixed material due to the high moisture content and the inability of standard chemical fixation to retain carbohydrate-based structures. 

CONTENTS Introduction to the Series An Editor s Foreword, Albert Padwa. Preface, C. Allen Bush. Raman Spectroscopy of Nucleic Acids and Their Complexes. George J. Thomas, Jr. and Masamichi Tsuboi. Oligosaccharide Conformation in Pro-tein/Carbohydrate Complexes, Anne Imberty, Yves Bourne, Christian Cambillau and Serge Perez. Geometric Requirements of Proton Transfers, Steve Scheiner. Structural Dynamics of Calcium-Binding Proteins, Robert F. Steiner. Determination of the Chemical Structure of Complex Polysaccharides, C. Abeygunawardana and C. Allen Bush. Index. 

W. M. Watkins Chemical structure, biosynthesis and genetic regulation of carbohydrate antigens retrospect and prospect... 

Owing to the weakness of carbohydrate receptor-protein interactions, in order to attain biological meaningful affinities for the receptor, carbohydrates very often need to be clustered and expressed in multiple copies. For this purpose glycodendrimers, which are multivalent glycoconjugates with well-defined chemical structures, have received recent attention for their considerable potential as tools for studying cell-surface protein-carbohydrate interactions, because of the affinity enhancement obtained by multivalency. 

The first of these compounds to be used in animal medicines, Tylosin, was isolated from Streptomyces fradiae. Its chemical structure which is typical of this group of compounds, is based on a lactone ring to which carbohydrate... 

Since neither the chemical nor the enzymatic synthesis alone can assist in the rational design of a new generation of therapeutic carbohydrate target structures, the chemoenzymatic approaches have been successfully utilized [40-42]. 

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