VOL. 12 (1953) BIOCHIMICA ET BIOPHYSICA ACTA 265 



PRECIPITABILITY OF SMALL QUANTITIES OF 



CELL CONSTITUENTS AND METABOLITES AS INSOLUBLE 



RADIOACTIVE COMPOUNDS* 



by 



C. NEUBERG and A. GRAUER 



Department of Biochemistry, New York Medical College, New York {U.S.A.) 

 and the Forschungsinstitut Gastein {A ustria) . 



Apart from physical methods, cyto- and histo-chemistry usually rely on visual 

 demonstration of objects by means of characteristic precipitations or stains. Examples 

 of this type are found in the long proven specific staining of certain cell constituents such 

 as the nuclei with basic dyestuffs. These cases are concerned with preformed objects 

 whereas in other instances the cell constituents to be determined are made visible by an 

 in situ transformation as e.g. in the Feulgen tests for polysaccharides, plasmogen and 

 desoxyribonucleic acid^'^. The staining technique is based on the isolation or transforma- 

 tion of primarily non-staining substances into staining compounds. This may be achieved 

 by purely chemical measures or by enzymes. Dubos and Bracket's method^ of demon- 

 stration of ribonucleates represents a method of the latter type. The enzyme ribonu- 

 clease is used to produce the characteristic staining compound from the ribonucleic acid 

 substrate. Conversely, enzymes may be determined, if they yield a specific, well defined 

 and staining reaction product. This applies to the technique of Takamatsu as well as 

 GoMORi^ for identification of phosphatases. In this process, phosphate enzymatically 

 produced from suitable phosphorylated substrates is transformed into black staining 

 cobalt- or lead-phosphate. This method of enzymic production of an insoluble precipitate 

 is based on the ability of the phosphatases to spht off insoluble alkahne earth phosphate 

 from various substrates such as calcium salts of sugar- or glycero-phosphates as first 

 shown and recognized as significant by Neuberg and collaborators^. 



The principal physical methods are specific absorption and electron microscope 

 photography of the objects to be demonstrated as well as manifestations of fluorescence. 

 Recently, radioautography has been added. This last method, however, preponderantly 

 indicates accumulation and migration in organs or tissues without demonstrating local- 

 ization of a process within a single cell. 



In the purely chemical as well as in the physical characterization of substances 

 either distinctly preformed or artificially produced in situ, conservation of the morpho- 

 logical locahzation as well as specificity of the reaction to be applied are prerequisites. 



* This investigation was supported by contracts of the U.S. Atomic Energy Commission and the 

 Office of Naval Research and the American Cancer Society on recommendation by the Committee of 

 Growth of the National Research Council with the New York Medical College. 



References p. 272. 



