Histochemical Identification of Sialic Acids

Techniques for the demonstration, investigation and identification of sialic acids, are based primarily upon the presence of two, histochemically reactive structural features in the molecule. These are the carboxyl group located at 

An alternative to methods based upon the chemical reactions of carboxyl groups or vicinal diols is the use of lectins labelled with peroxidase or fluorescent tags. Such procedures have been little exploited in the histochemical investigation of sialic acids and indeed have specificity problems peculiar to the mechanism of their reaction but they would appear to be a promising approach to the identification of sialic acids. 

Finally it must be remembered that, in common with all histochemical procedures, the absence of a discernible reaction does not necessarily mean absence of the reactant sought, but only that the reactant is not present in sufficient concentration to produce a sufficient density of colour that can be seen by conventional means. It should also be realized that while absolute specificity may not be possible, there are the instances in which the presence of staining together with the morphological site of occurrence, will provide relative specificity. 

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The C.E.C. methods developed by Scott and his colleagues (Kelly et al. 1963, Scott and Dorling 1965) whereby a selective staining of various anionic groups is achieved by the use of staining baths containing various concentrations of salts are not in routine use for the histochemical identification of sialic acid. 

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