84 NUCLEIC ACIDS AND NUCLEOPROTEINS 



The organic chemist, the biochemist, the crystallographer, the 

 biologist often look at the same object and they may even use 

 the same term, but they mean different things. Our natural 

 sciences, which once could find room in a single brain, have 

 grown diffuse and multilingual. We are faced with a real problem 

 of translation: from the molecular to the submicroscopic level; 

 and then, in turn, to microscopic structures, morphological units, 

 organelles, cells and cell communities. Where and when shall we 

 find the dictionary that could help us in these translations? I 

 should say, probably not before biochemistry has earned the first 

 half of its name. It is, of course, not surprising that such a term 

 as "nucleic acid" does not carry the same connotation in the 

 several disciplines. A sculptor and a tailor naturally have dif- 

 ferent ideas of what makes a man: one looks at the torso, the 

 other at the pants. 



Nevertheless, we must be content with avoiding the avoidable 

 and use the means that our science has given us. It is time for 

 me to speak of nucleic acids. 



3. TWO TYPES OF NUCLEIC ACID 



You all know that the convenient slang terms DNA and RNA 

 stand, respectively, for deoxyribonucleic and ribonucleic acids*. 

 If this were a more strictly chemical talk I would point out that 

 the sugars have been identified in only a few cases and that a 

 more neutral designation, such as deoxypentose and pentose 

 nucleic acids, would be safer. But tonight we may disregard that, 

 as the nature of the sugars occurring in the nucleic acid speci- 

 mens of which I am going to speak has in almost all cases been 

 verified. 



When about ten or eleven years ago my colleagues, first of all 



* The following abbreviations will be used: DNA, deoxypentose nucleic 

 acid(s); PNA, pentose nucleic acid(s); A, adenine; G, guanine; C, cytidine; 

 MC, 5-methylcytosine; T, thymine; U, uracil (or the corresponding nucleo- 

 tides); Pu, purines; Py, pyrimidines; 6-Am, adenine + cytosine; 6-K, 

 guanine + uracil. 



