174 SESSION II. DISCUSSION 



M. Vol'kenshtein (U.S.S.R): 



In connection with Prof. Terent'ev's contribution I should hkc to make the following 

 remarks. 



The role of asymmetry, i.e. the stereochemical fixity of macromolccular structures in 

 biology, is extremely important. Asymmetry ensures more accurate and richer methods 

 of recording information and passing it on in the process of self-reproduction. Life, 

 as we know it now, has no other methods. Racemic life may be considered to be no more 

 than a speculative idea. 



The problem may be broken down into the following questions: 



1. What possible causes could there have been for the formation of pure optical anti- 

 podes on the surface of the Earth? Were these causes biogenic or abiogenic? 



2, What were the causes for the accumulation in the biosphere of particular antipodes 

 of the original vitally imponant substances? 



I believe that pure antipodes can be produced without biogenesis and that therefore, 

 for biological problems it is only necessary to answer the second question. Let us, however, 

 begin by considering the first for a while. 



Local asymmetry of chance origin is commonly found in inorganic nature, for example, 

 in beds of quartz. The reasons for this are quite obvious. 



I agree with Prof Terent'ev that catalysis on the surface of asymmetric crystals might 

 lead to the appearance of pure antipodes of simple organic molecules, in particular, amino 

 acids. Their formation can, however, hardly be attributed to the phenomenon of circular 

 dichroism. As concerns this phenomenon, the position of inorganic and living nature 

 should be the same in principle. However, asymmetry is only produced in the latter. 

 On the other hand the degree of circular polarization in scattered and reflected light on the 

 surface of the Earth is very slight and such circular polarization could hardly be the 

 cause of the asymmetry which we can observe. 



To my mind we must include among the sources of asymmetry thermodynamic 

 fluctuations in the concentrations of pure antipodes. How did they accumulate in the 

 biosphere? 



One can give a number of reasons why life should, in principle, make use of large 

 rather than small molecules — polymers rather than monomers. In this connection stress 

 should be laid on the great importance of recent work by the Italian chemist Natta on 

 the synthesis of so-called isotactic and syndiatactic polymers, which are chain-like macro- 

 molecules with stereochemically fixed structures. Stereospecific catalytic synthesis 

 probably also forms the basis of life. 



Originally life also developed in alternative ways at random, probably being right- 

 handed in some parts of the world and left-handed in others. Later, evolution led to the 

 disappearance of one of these forms. Why? Probably because tlie evolutionary process, 

 which could originally follow either the dextro or laevo path, when once started in a 

 particular course could not stop and did not alter its course. There is thus no difficulty 

 in imagining the existence of life, exactly equivalent to our own, but based on the opposite 

 antipodes. 



In conclusion, it must be pointed out that any proper scientific study of the problem 

 of the accumulation of asymmetry during the process of evolution should begin with the 

 study of irreversible processes using thermodynamic methods. Professor Prigogine's 

 address will be devoted to this field of physics and the application of such ideas to biology. 



A. G. Pasynskiï (U.S.S.R.): 



The Asymmetry of Organic Substances 



As A. I. Oparin maintained, one of the fundamental problems with which the Sympo- 

 sium is concerned is that of the emergence of asymmetry among organic compounds. The 

 interesting papers of Terent'ev & Klabunovskiï, to which we listened yesterday and to-day 

 and also the contributions of Akabori and others to come, deal with this subject. From 

 their evidence it is clear that a considerable degree of asymmetric synthesis and resolution 



