The Role of Dissymmetry 75 



K2Cr207, CuoO, Ba(N03)2 and Pb(N03)2 [i]. Antipodes differ from racemates 

 in the form of their crystals, their solubility and their melting points. The pre- 

 sence of several centres of dissymmetry in one structure is the reason for the 

 existence of many diastereoisomers with different physical and chemical 

 properties. It has been shown, e.g. that the polymerization of the amino acid 

 derivatives, (— )-propylene oxide [2] and (— )-a-methylbenzyl methacrylate [3] 

 leads to the formation of polymers which differ in their properties according to 

 whether they were made from a pure antipode or a racemate. 



These special properties of optically active compounds provide the necessary 

 conditions for some other factors which are not present in substances with sym- 

 metrically constructed molecules. These peculiarities and the behaviour of op- 

 tically active substances may be termed the 'Pasteur effect' since Pasteur first 

 drew attention to them. 



The reasons for tliis effect are primarily determined by the configurations and 

 conformations of the molecules. When they interact with one another, dissym- 

 metrical molecules form crystalUne or colloidal soHd bodies with different 

 'packings' depending on the nature of the dissymmetry. Not surprisingly, the 

 bonds between the molecules, which are responsible for the Pasteur effect, are 

 extremely labile. 



There can be no doubt that, in biochemical processes involving compUcated 

 molecules with many centres of dissymmetry, the Pasteur effect must be very 

 important. Maybe the first protein manifested the characteristics of Ufe owing 

 to the presence of a definite sequence in the arrangement of residues of dissym- 

 metrical molecules of amino acids. 



THE ORIGIN OF DISSYMMETRY IN 

 PRIMAEVAL PROTOPLASM 



Let us try to answer the second question: How could dissymmetry have arisen 

 in the primaeval protoplasm ? 



Various ways by which optically active substances may be obtained abio- 

 genically are known. 



In the first place : the resolution of a racemate by the spontaneous crystal- 

 lization of one antipode from a solution of the racemate. This method need 

 hardly be taken into account in connection with the complicated substances of 

 colloidal structure which undoubtedly played the essential part in the building 

 up of the primaeval protoplasm. 



In the second place : the chemical action of circularly polarized ultraviolet 

 light. By this means Kuhn and other authors have succeeded in bringing about 

 a number of absolute asymmetric syntheses with appreciable optical activity. 



In spite of the insignificant predominance of the right circularly polarized 

 component in the scattered light falling on the surface of the Earth, this action 

 must surely have made itself felt during the long years of the evolution of the 

 living world. 



We consider that this factor must be taken into account in connection with 

 the problem under discussion and more will be said about this later. 



