268 



L. A. NIKOLAEV 



The activation of a structure is an important factor in biochemical evolutionary 

 selection and it may be supposed that from the multitude of different compounds 

 which developed at different periods when only the simplest forms of Ufe were 

 established, it was just those structures which had the greatest capacity for 

 being activated which were of the greatest biochemical value. The process of 

 biological evolution must have reached its greatest intensity' in just those organ- 

 isms in which the vitally important catalysts were composed of compounds 

 which could be markedly activated. It is not by chance, either, that it is in those 

 organisms which have attained a high degree of development that we find, among 

 the catalysts which regulate their vitally important processes, complex com- 

 pounds of iron and copper having a specially great activating power. 



150 



Fig. 3. The dependence of ajM on M for complex compounds of copper with 

 heterocyclic substances. 



This phenomenon can be regarded from two points of view. In the first place, 

 it is a reasonable assumption that when we act on a particular point of the 

 molecule of a biologically active material and thereby alter its activity, we are 

 interfering with the very part of the molecule which subserves its activity. In 

 the pyridine molecule for example, the susceptible point seems to be the nitrogen 

 atom. In the second place, one may see in the structural sensitivity of biocata- 

 lysts and 'working' models of them, the characteristic features of 'internal 

 association' of some of their structures. 



The internal association of the atoms in particular molecules or parts of 

 molecules is a fact which it is hard to deny. Thus, the diamagnetism of phthalo- 

 cyanin and its derivatives gives rise to the idea of electronic currents within the 

 molecule joining together particular atoms. 



Considerable alterations in the absorption spectra of many biologically active 

 substances may be brought about by comparatively small changes in any single 

 place in the molecule. These phenomena, which have been studied in detail in 

 the chemistry of dyestuffs, are evidence for a close interaction between the 

 electronic systems of atoms comprising a molecule. 



Holland [9] has recentiy shown that the characteristic absorption spectra of 



