The Problem of Stages in Biopoesis 39 



from sub-microscopic to a few millimetres, offers considerable justification for 

 the hypothesis of Oparin [6] that the formation of coacervates formed one stage 

 in the development of Ufe, They would appear as a natural consequence of the 

 formation of even irregular and polydisperse polymer molecules of protein. In 

 so far as each coacervate drop contained most or all of the reactants and enzymes 

 necessary for mutually supporting chemical reactions and could carry them out 

 in the dilute medium from which it was precipitated, it qualifies as a self-sub- 

 sisting system. However, as it was indefinitely divisible or miscible with other 

 drops and possessed no mechanism for ensuring its reproduction it hardly 

 qualifies as an organism and might well, following Pirie [2], be termed an eobiont. 



If the physical consequences of polymerization made possible the existence of 

 long-Hved independent aggregates, its chemical consequences can have given 

 rise to a more advanced characteristic of Ufe, the regularization and fixing of 

 reaction chains in the eobiont. Here evidence is accumulating that the key role 

 was played by the polynucleotides or nucleic acids or perhaps by their possible 

 precursors the polymetaphosphates or organo phosphates — phosphate groups 

 Unked by some polyalcohol, possibly as simple as glycerol and phosphoglyceral- 

 dehyde. The essential feature of any such system of Unking is that the energy- 

 transferring power of the phosphate group is not lost. As Bresler [15] has shown, 

 nucleic acid can be diphosphatized reversibly just as can a single nucleotide. 

 At the same time a new formal element is introduced when two different nucleo- 

 tides or proto-nucleotides are coupled — the possibiUty of a topochemical reaction 

 specifically dependent on the order of Unking of the nucleotides. This is the 

 germ of the evolution of order and reproducibility in Uving systems. The degree 

 of reproducible order we see now is very great; it cannot have been so at the 

 outset. But further elucidation of the reciprocal relations of synthesis between 

 proteins and nucleic acids should help to show how such a high degree of order 

 could be built up step by step, from lower degrees. 



Polymers, and especiaUy ordered polymers, can acquire another form of 

 regularity over and above that of the sequence of their monomers. According to 

 the geometrical and chemical character of the identical repeating imit and its 

 various residues, the polymer chain assumes one or many configurations deter- 

 mined stericaUy and through internal hydrogen bonding. In this way discrete 

 spirals such as the Pauling [7] a-helix of fibrous proteins can be built up as 

 weU as the more complex two- or three-strand twining of deoxyribose nucleic 

 acid (DNA) and coUagen. Further coiled-coiling or folding can lead to discrete 

 quasispherical molecules like those of the globular proteins with their potential 

 enzyme activities. These in turn can become redupUcated and aggregated to form 

 larger molecules and intracellular structures in a way discussed in more detail 

 in my second paper. Here it is is sufficient to recaU that the smaU globular 

 proteins can aggregate almost as do separate atoms with different valencies. 

 Univalent associations lead to doubled molecules as in the haemoglobins, bivalent 

 association to chains and rings as in insulin, tervalent association to sheets or 

 basket-like forms as found in viruses, multivalent association to clumps such as 

 occur in haemocyanin. The associations can be of various degrees of stability, 

 dependent on the nature of the surrounding medium, or they can become vir- 



