SESSION IV. DISCUSSION 375 



G. Schramm (Federal German Republic) : 



To begin with, I want to thank Dr. Belozerskiî for his remarks. I am very glad that our 

 ideas about metaphosphates are not altogether mistaken. I should like to speak about the 

 application of serological methods to the study of viruses. We have used the methods 

 extensively in looking for the absence of proteins from preparations of nucleic acids. By 

 means of the complement-fixing reaction it is possible to detect a very small amount of 

 viral protein J the preparations of nucleic acids which we obtained by the phenol method 

 contained less than o-02% of viral protein. The detection of smaller amounts of protein 

 in larger amounts of nucleic acid would be hard by chemical means. Infectious ribonucleic 

 acid was also prepared from several animal viruses such as poHomyelitis virus (Colter, 

 Bird, Moyer, Brown) and meningo encephalitis virus (Colter, Bird, Brown) and eastern 

 equine encephalitis virus (Wecker, Schäfer). 



As I understood, Dr. Fraenkel-Conrat studied the decrease in infectivity of the virus 

 and of the nucleic acid obtained from the virus after unltrasonic treatment. I do not 

 doubt the correctness of liis results. They may be explained by the separation of part of 

 the protein from the virus particles under the influence of ultrasonic vibrations. The 

 infectivity of the protein-containing material would then become less, while the nucleic 

 acid, if it had not already been damaged, might remain infective. I think that one should 

 use the method worked out by Williams to calculate the number of short particles and then 

 establish a relationship between infectivity and the number of short particles. Dr. Fraenkel- 

 Conrat emphasized that these experiments were only just beginning and we must await 

 further facts. 



V. S. ToNGUR (U.S.S.R.): 



The formation and properties of nucleoproteins, especially deoxyribonucleoproteins 

 (DNP), have been far too httle studied. Moreover, it is not clear what is the quantitative 

 relationship between protein and deoxyribonucleic acid (DNA) in the formation of DNP. 

 How are the properties of DNP changed when there are changes in the amount of protein 

 in it ? and so on. Together with L. S. Diskina and D. M. Spitkovskiï at the Institute of 

 Experimental Biology, I have made an attempt to study some of these problems. We 

 wanted to find the point of inversion, i.e. the point at which a molecule of DNP is con- 

 verted into a molecule of DNA by measuring the viscosity of DNP which was being 

 gradually deproteinized. (The DNP was prepared from the liver and pancreas of oxen.) 

 The results showed that, over a fairly wide range of protein-content in DNP (from 70-75% 

 down to about 25%) achieved by repeated deproteinization, the viscosity, and, therefore, 

 also the form of its molecules, remained unchanged, i.e. the tertiary structure of DNP 

 has a reasonably good configurational stability. However, if the protein content of the DNP 

 is further lowered (to 15-25%), there is a sharp rise in the viscosity, which increases to 

 about twice its former value. When this happens, according to our hypothesis, there is 

 a transition from the tertiary structure of DNP to the tertiary structure of DNA. If the 

 experiment is carried out in the reverse direction, that is to say by combining DNA with 

 various proteins, then inversion takes place when the ratio of DNA to protein is about 

 the same and the DNP and the complexes of DNA which are formed have a viscosity 

 considerably lower than the original viscosity of the DNA. The actual viscosity of the DNP 

 depends on the nature of the protein which enters into the artificial complex. This would 

 appear to indicate that, on combination with DNA, each protein forms the tertiary 

 structure of DNP, having a different specific packing according to the nature of the 

 protein component. Thus, the tertiary structure of DNP appears, according to our view, 

 when protein is present in the complex to the extent of about 15-25%, and the molecule 

 which contains components in this proportion to one another may be called the true 

 molecule of nucleoprotein. 



It is not without interest to note that the so-called 'residual protein' of DNP consti- 

 tutes about 15-20% of the weight of the DNP. This encourages the idea, though, to be 

 sure, it is still only a speculation, that the tertiary structure of DNP is maintained by the 



