134 LIFE: ITS NATURE AND ORIGIN 



ing the transformation of pneumococcal types isolated from Pneu- 

 mococcus Type III, is "in the form of a desoxyribonucleic acid frac- 

 tion. The data obtained by chemical, enzymatic, and serological 

 analysis, as well as by electrophoresis and ultracentrifugation of the 

 purified material, strongly suggest that the nucleic acid is itself respon- 

 sible for the biological activity." Minute amounts of this substance 

 can cause uncapsulated "rough" variants of Pneumococcus Type II to 

 acquire the capsular structure and type specificity of Pneumococcus 

 Type III. Ascorbic acid (and other autoxidable compounds, e.g., 

 catechol, hydroquinone, p-phenylenediamine) inactivate the trans- 

 forming substance. 



With ascorbic acid inactivation is catalyzed by traces of cupric ion; 

 this is prevented by the presence of sulfhydryl compounds, which can 

 restore activity under certain conditions. Activity is irreversibly 

 destroyed by highly purified preparations of the specific enzyme 

 desoxyribonuclease, capable of depolymerizing authentic samples of 

 desoxyribosenucleic acid of animal origin. The enzyme requires the 

 presence of a metallic activator (in nature magnesium, though man- 

 ganese in like molar concentration is equally effective). The specific 

 transforming substance isolated from pneumococci of types II and VI, 

 in addition to type III, consists of desoxyribonucleic acid as the bio- 

 logically active substance. "Although the individual desoxyribo- 

 nucleates of different types cannot yet be distinguished from one an- 

 other on chemical grounds, the selective specificity they exhibit in 

 inducing transformation is difficult to interpret save in terms of indi- 

 vidual differences in chemical structure and molecular configuration." 91 



As pointed out in Chapter 3, note 1, naturally occurring carote- 

 noids having seven double bonds may have 128 possible stereo- 

 isomers. With 12 stereochemically effective double bonds the 

 number of possible isomers rises to 2800 for symmetrical chains, 

 and 4096 for unsymmetrical chains. How stereoisomerism can 

 affect the properties of substances having the same ultimate 

 chemical analysis may be seen from the following excerpts from 

 the review of L. Zechmeister of the California Institute of Tech- 

 nology. 92 



"A long conjugated double-bond system offers many spatial 

 possibilities, but the synthetic as well as the natural polyenes are 

 usually a\\-trans compounds. . . . This configuration can be easily 

 altered by various thermal, photochemical, or catalytic treatments. 

 Upon such treatment the stereochemical uniformity of the mole- 

 cules disappears and a complicated mixture of cis-trans isomers is 

 formed, in which ordinarily the unchanged portion of the initial 



