Publisher Summary This chapter discusses the chemistry, metabolism, and biological functions of sialic acids. Interest in the sialic acids has rapidly increased in recent years, especially because of the reorganization of their involvement in the regulation of a great variety of biological phenomena. The occurrence of sialic acids in plants has never unequivocally been established, although some positive reports exist. The acylneuraminic acids can be released from their glycosidic linkages either by dilute (aqueous or methanolic) acids or sialidases. The unequivocal determination of sialic acids occurring in low concentrations in many biological materials is rather difficult, and this explains the many errors that have been made in this field. The biosynthesis of N-acetylneuraminic acid (Neu5Ac) is briefly reported in this chapter and more attention is given to the enzyme reactions modifying this compound. Little information is available about the role of the modifications of sialic acid resulting in a species- and tissue-specific distribution of different N,O-acylated and O-methylated sialic acids.

Chemistry, Metabolism, and Biological Functions of Sialic Acids

Publisher Summary This chapter describes that mass spectrometry (m.s.) has become an important and versatile technique in carbohydrate chemistry. The chapter deals with m.s. as a tool in the structural analysis of naturally occurring carbohydrates. The mass spectra of permethylated methyl glycosides show ions derived from a number of specific degradation pathways. These fragmentations have been carefully studied in the chapter, by using deuterium-labelling techniques. Direct derivatization of reducing sugars by permethylation, peracetylation, or per( trimethylsilyl )ation gives a mixture of glycosides. These derivatives are suitable for g.1.c. analysis, although, for complex mixtures of sugars, the multiplicity of peaks caused by the derivatization may complicate elucidation of the results. The partially methylated sugars are separated and converted into the methyl glycosides, and these are methylated with trideuteriomethyl iodide. The substitution pattern of the trideuteriomethyl groups can be determined by m.s., and the nature of the sugar ascertained by g.1.c. (by comparison with the permethylated compound used as the reference sample).

Mass Spectrometry in Structural Analysis of Natural Carbohydrates

Characterization of sialic acids.

Biochemical, medical, and environmental applications of field-ionization and field-desorption mass spectrometry

Precision polysaccharide synthesis catalyzed by enzymes.

Mass spectra of acetylated derivatives of sialic acids

Unsaturated carbohydrates : Part XIII. The mass spectrometry of hex-2- and hex-3-enopyranosyl derivatives

Some esters of γ, δ-unsaturated or β-arylsubstituted acids undergo a peculiar transformation under electron-impact including an elimination of the alcohol residue as a radical R. with the following loss of the ketene molecule. One of the oxygen atoms of the carbonyl group enters an ion which is formed from an unsaturated part of the molecule. The possible mechanism of this reaction and the influence of structural modifications on the course of this process are discussed.

The oxygen rearrangement of aromatic and unsaturated esters under electron‐impact—I: General regularities of the rearrangement

The chemical ionization mass spectra of various aliphatic nitro compounds have been studied. Almost all the nitro compounds form stable [M+H]+ ions in sharp contrast to the instability of their ions produced by other ionization techniques. The fragmentations of the [M+H]+ ions are discussed, the mechanisms and structures of fragment ions proposed being supported by quantum mechanical calculations. Correlations between chemical ionization mass spectra and structures of compounds studied are outlined. Reliable identification of mono- and polynitroalkanes and some related derivatives may be made by analysis of their chemical ionization mass spectra.

V. I. Kadentsev

Papers

Mass spectra of acetylated derivatives of sialic acids

Unsaturated carbohydrates : Part XIII. The mass spectrometry of hex-2- and hex-3-enopyranosyl derivatives

The oxygen rearrangement of aromatic and unsaturated esters under electron‐impact—I: General regularities of the rearrangement

Chemical ionization of aliphatic nitro compounds

Synthesis and some properties of gem-dichlorocyclopropane carboxaldehyde acetals and cyclopropane carboxaldehyde acetals