PHOSPHORIC esters play a central part in the biological world bY linking processes of respiration and fermentation with other essential cellular reactions. More tnan twenty substances of this group, mainly sugars and related substances esterified with phosphoric acid, are known to form intermediate in the network of enzymic reactions associated with the breakdown and interconversion of carbohydrates in plants and animals. Both in the intact cell and in the isolated enzyme systems in which these reactions are studied, phosphoric esters usually occur in mixtures, and progress in this important field has depended upon the development of methods for identifying and determining the individual esters present in such mixtures. Existing methods of analysis depend mainly upon the fractionation of salts of the esters and the selective hydrolysis of some of them, under standard conditions, these procedures being supplemented when possible by methods based on more specific reactions given by particular esters. Except when applied to certain relatively simple mixtures, these methods frequently fail to yield diagnostic results.

Separation of the Phosphoric Esters on the Filter Paper Chromatogram

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The free amino groups of insulin.

THE use of ammoniacal silver nitrate solution as a spraying reagent for revealing the presence of sugars on filter-paper chromatograms1 has the advantage of general application ; but it has a corresponding disadvantage in reacting with a very wide range of reducing substances other than the sugars, including various impurities commonly present in such solvents as phenol and collidine. Two-dimensional chromatograms are often rather unsatisfactory when ammoniacal silver nitrate is used, because (a) a rather large amount of the sugar mixture is needed and this increases the effect of interfering substances, (b) it is necessary to apply the spray as an aqueous solution, and unless the spraying is very rapid and uniform, the sugar spots migrate from wet to dry regions on the filter paper.

A. H. Gordon

Papers

Qualitative analysis of proteins: a partition chromatographic method using paper.