b I. LESLIE 



2. Procedure of Schneider (1945) 



In the Schneider^ procedure (Table I) the PNA and DNA are extracted 

 together by means of hot (90°) TCA or PCA,'^ thus freeing them from most 

 of the tissue protein which remains insoluble (X). As both nucleic acids are 

 hydrolyzed to their constituent nucleotides or free bases (IX), there is no 

 means of separating them. Instead they are determined on the basis of 

 specific color reactions for pentose and deoxypentose. 



Schneider" carried out an extensive series of parallel determinations on animal 

 tissue using his own and the Schmidt and Thannhauser procedures, and found rea- 

 sonably good agreement between the two methods. According to Mclndoe and 

 Davidson, 3* the Schneider treatment splits off from the protein residue all the re- 

 active sugar components, leaving appreciable amounts of P bound to the protein 

 residue (X). If the extraction is made with hot PCA, there is the danger of appreci- 

 able contamination of the extract by protein and its breakdown products. ^^ 



Logan el al.^^ also report good agreement between the Schmidt and Thannhauser 

 and the Schneider procedures as applied to pancreas, spleen, thymus, white blood 

 cells, and reticulocytes, although wide discrepancies are found between parallel 

 determinations on brain or nerve tissue. Phosphoprotein, an inositide-P complex, and 

 unspecified chromogenic materials are apparently present in substantial amounts in 

 nerve tissue and interfere with the determinations. In these circumstances a combina- 

 tion of the two procedures involving ultraviolet absorption measurements of fractions 

 VII and IX proved the most reliable means of determining PNA and DNA. The 

 amount of DNA could be obtained directly from fraction VII. A duplicate sample of 

 tissue was put through the Schneider procedure and PNA determined from the 

 difference (IX-VII). The Schneider procedure gave very high values for PNA (orcinol 

 method) when applied to serum''; on the other hand, for samples of yeast cells it gave 

 lower values for PNA than those obtained by the Schmidt and Thannhauser pro- 

 cedure.'"* Ogur et aZ.'" report the extraction of total nucleic acid and metaphosphate 

 from yeast residues by three extractions with 5% PCA at 70°. 



Two micro-modifications of the Schneider procedure have been developed. The 

 method of Steele et al.*^ requires special micro-equipment and covers the range of 

 9 to 58 fig. PNA and 1.6 to 15 fig. DNA. Patterson and Dackermann*' employed the 

 micro-equipment of Linderstr0m-Lang and Holter'''' and measured the nucleic acids 

 of Drosophila salivary glands in amounts of 1 to 2 ng. DNA and 10 to 20 ng. PNA. 



3« W. C. Schneider, G. H. Hogeboom, and H. E. Ross, /. Natl. Cancer Inst. 10, 977 



(1950). 

 " W. C. Schneider, J. Biol. Chem. 164, 747 (1946). 

 '8 W. M. Mclndoe and J. N. Davidson, Brit. J. Cancer 6, 200 (1952) . 

 39 R. H. Common, D. G. Chapman, and W. A. Maw, Can. J. Zool. 29, 265 (1951). 

 "0 A. Bourdet, P. Mandel, and R. Guillemet, Compt. rend. 232, 756 (1951). 

 ■" M. Ogur, S. Minckler, G. Lindegren, and C. C. Lindegren, Arch. Biochem. and 



Biophys. 40, 175 (1952). 

 « R. Steele, T. Sfortunato, and L. Ottolenghi, /. Biol. Chem. 177, 231 (1949). 

 " E. K. Patterson and M. E. Dackermann, Arc/i. Biochem. and Biophys. ZQ, 97 (1952). 

 ** K. Linderstr0m-Lang and H. Holter, in "Die Methoden der Fermentforschung" 



(E. Bamann and K. Myrback, eds.), p. 1132. Thieme, Leipzig, 1940. 



