Analysis bound carbohydrates

Mrochek, J. E., Dinsmore, S. R., Tormey, D. C., and Waalkes, T. P., Protein-bound carbohydrates in breast cancer, liquid-chromatographic analysis for mannose, galactose, fucose, and sialic acid in serum, Clin. Chem., 22, 1516, 1976. 

Analysis showed that the snail agglutinin contained a preponderance of acidic and hydroxylic amino acids and a large proportion of proline residues.83,560-562 Uncharacteristic of lectins from leguminous-plant seeds, the hemagglutinin contained 18 half-cystine residues and 10 molecular proportions of methionine per molecule of protein.83,569 About 8% (by weight) of covalently bound carbohydrate was found this was principally D-galactose and D-mannose.63... 

One special feature in the interpretation of the quantitative results seems not to have been exploited in practical analysis, and it certainly deserves attention. The result of the methylation analysis is sometimes complex, and can reveal the occurrence of 10 to 20 different methylated sugars. In this situation, it is not easy to decide, by simple inspection of the analytical data, whether the result could be caused by one complex, carbohydrate chain, or by a structure containing several saccharide chains bound to a common aglycon. In addition, it is not always easy to decide whether the result could fit any natural structure, or mixture of structures, or whether the complex result is attributable to undermethylation. 

In principle, mass spectrometry is not suitable to differentiate enantiomers. However, mass spectrometry is able to distinguish between diastereomers and has been applied to stereochemical problems in different areas of chemistry. In the field of chiral cluster chemistry, mass spectrometry, sometimes in combination with chiral chromatography, has been extensively applied to studies of proton- and metal-bound clusters, self-recognition processes, cyclodextrin and crown ethers inclusion complexes, carbohydrate complexes, and others. Several excellent reviews on this topic are nowadays available. A survey of the most relevant examples will be given in this section. Most of the studies was based on ion abundance analysis, often coupled with MIKE and CID ion fragmentation on MS " and FT-ICR mass spectrometric instruments, using Cl, MALDI, FAB, and ESI, and atmospheric pressure ionization (API) methods. 

In general, it is very difficult reliably to extract and quantitate multiple vitamins from complex food systems, due to their diverse physical and chemical properties. Consequently, the extraction of the vitamins from the food matrix is usually the greatest challenge of vitamin analysis. This is especially true for the naturally occurring vitamins, which are often bound to other food constituents, such as carbohydrates or proteins. To prevent vitamin degradation or loss, the extraction conditions should complement the labile nature of the vitamins. Indiscriminate mixing and matching of extraction and quantitation methods is not recommended, since the extraction conditions can affect subsequent separation and quantitation steps. 

For some foods, incomplete extraction of color is obtained, probably due to the high binding affinity of dyes to the bulk of the food matrix, especially to proteins, lipids, and carbohydrates (156,161,162). This problem can be overcome by the use of selected solvents or enzymes to digest the food prior to extraction. Petroleum ether can be used to extract lipids (163). Acetone can be used to remove lipids and coagulate protein (164). Enzymes, such as amyloglucosidase (165,166), papain (167), lipase, pectinase, cellulase, and phospholipase, added to the sample and incubated under optimum pH and temperature conditions release synthetic colors bound to or associated with the food matrix. Furthermore, enzyme digestion can solubilize some foods, enabling analysis to be continued (156). 

Many studies have indicated that covalent linkages must exist between lignin and wood polysaccharides. Separation and analysis of lignin -carbohydrate complexes (LCC) have led to the conclusion that the hemicel-lulose components (xylan and galactoglucomannans in softwood) are bound to lignin mainly through arabinose, xylose, and galactose moieties as shown in Fig. 4-10. 

A third group of ion-exchange supports are pellicular, consisting of a solid inert core made of PSDVB agglomerated with 350 nm functionalized latex. The quaternary amine groups are closely and uniformly bound on the microbeads, improving flow and reducing nonspecific retention. These pellicular supports are primarily used for carbohydrate analysis [7]. 

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