Bernard A. Koechlin

The separation of the proteins of human plasma into a series of fractions and subtractions, uniform with respect to certain physical properties, has gen- erally led also to the separation of proteins with respect to their chemical and biological properties. Among the properties that have long been recog- nized has been the binding of metals by the plasma so that the metals were no longer freely dialyzable (1). When plasma fractionation was undertaken, early in the war, the Committee on Blood Substitutes of the National Research Council were informed that "investigations of the distribution of . . . metals known to be combined with proteins in the blood, such as copper, zinc, and iron, are planned and will be subsequently reported, as will studies upon the hormones and other physiologically important components of human plasma for which methods of bio-assay are available. We feel keenly that these should now be studied in the large amounts of human plasma fractions becom- ing available as by-products of the preparation of human albumin for transfusion in shock" (2).

Investigations dealing with the determination of the major chemical constituents of the axoplasm of the giant nerve fiber of the squid are described. Particular emphasis has been placed on determining the components involved in acid-base balance. It was found that 72 per cent of the total solids of axoplasm, representing 13.5 per cent of the wet material, are of relatively low molecular weight (dialyzable) and consist mainly of charged ionic or dipolar constituents. Of the 520 micromoles per gm. of total base, 72 per cent are balanced by organic acids: aspartic acid (65 micro equivalents per gm.), glutamic acid (10 micro equivalents), fumaric and succinic acids (15 micro equivalents), a new polycarboxylic acid (35 micro equivalents), and isethionic acid, a biologically novel sulfonic acid (220 micro equivalents). Besides potassium, sodium, small amounts of calcium, and magnesium there is a considerable fraction of organic (nitrogenous) base. Other features of the chemical composition of squid axoplasm include a relatively high concentration of taurine (100 micro equivalents) and an ultraviolet absorbing substance possibly identical with N-methylpicolinic acid. The distribution of the phosphates, especially the concentration of ATP, has been investigated. Specific techniques elaborated in connection with this study have been described and the biochemical implications of the analytical results are discussed.