PROPERTIES OF COMPLEX COACERVATES gOQ 



lead to the layering and separation of their solutions into 

 two liquid phases. 



According to H. L. Booij and colleagues,"^ the stability 

 and the length of time for which coacervate drops can remain 

 unchanged does not only depend on the concentration of 

 H"*" and OH~ ions but also on the presence of other electro- 

 lytes. 



The particular ratio bet^veen univalent and bivalent 

 cations is specially important. This is a manifestation of the 

 pronounced antagonism between cations which has been 

 studied in such detail in biological objects. Non-electrolytes 

 can have a stabilising effect on both simple and more com- 

 plicated coacervates by removing water from the colloidal 

 particles. For example, coacervate drops of gelatin and gum 

 arable may be kept in the equilibrium liquid for an indefinite 

 time in the presence of a solution of sucrose. ^^ 



A coacervate of gelatin and gum arabic is the classical 

 example on which Bungenberg de Jong did most of his work. 

 A number of later ^vorkers have also used such coacervates 

 for their experiments, among them D. G. Dervichian," who 

 confirmed the essential results of Bungenberg de Jong. 



Gelatin can, however, form coacervates with other carbo- 

 hydrates as well as gum arabic, e.g. gum acacia,-* araban 

 and agar, and also with starches from various sources." As 

 the introduction of phosphoric acid into the molecule of 

 starch markedly increases its negative charge, phosphorylated 

 starches very readily form coacervates with gelatin.-® Gum 

 arabic also readily forms coacervates with other proteins. 

 Dervichian" obtained a coacervate which was stable between 

 pH 30 and pH 3-8 from gum arabic and haemoglobin. Gum 

 arabic forms two different coacervates Avith cltipeine, one of 

 which occurs at pH 5 and the other at pH 7. 



We are specially interested in complex coacervates made 

 from two or several proteins. All that is necessary for these 

 to be formed is that, at some particular pH, their particles 

 shall bear charges of opposite signs. This is easily achieved 

 by mixing solutions of acidic and basic proteins. The greater 

 the difference between the isoelectric points of the proteins 

 used in the experiment, the more readily will they form 

 coacervates. For example, good coacervate drops can be made 



