H. P. WOLVEKAMP 



reversibly bound, ferricyanide has to be replaced by potassium mercuric 

 cyanide which gives with haemocyanin a compound named cyan- 

 haemocyanin which does not combine with oxygen. 



Carbon monoxide is bound but the affinity for this gas is very small. 



Investigations chiefly carried out by The Svedberg et al 2 and by 

 J. Roche 3 with their co-workers on the molecular weight, the absorption 

 spectra in visible and ultra violet light, the chemical composition, the 

 titration curves and the position of the isoelectric point, indicate 

 typical specific and even intra-specific differences between the haemo- 

 cyanins. 



Finally the mode of oxygen binding still shows characteristic specific 

 differences when solutions of purified haemocyanin are investigated. 

 The shape and position of the oxygen dissociation curves are strongly 

 influenced by the presence of salts, and the reversible breaking up of 

 the enormous molecules in definite pH ranges presents a complication 

 not found in concentrated solutions of haemoglobin of vertebrates. 



Every conceivable type of dissociation curve has been obtained by 

 investigators working on haemocyanin. In the first place dialyzed 

 solutions of haemocyanin of the edible snail yield a simple hyperbolic 

 curve at different pH thus indicating that the prosthetic groups of each 

 molecule have the same affinity for oxygen and do not mutually 

 influence each other (Stedman and Stedman 1 1928). The dissociation 

 curve of the blood of the same animal, however is typically s-shaped 

 (Stedman and Stedman 1 (1929), Wolvekamp and Kersten 4 ). Redfield 

 and Miss Ingalls 1 (1933) in a series of very careful experiments 

 obtained several undulatory curves (Figure 1). The shape of the curves, 



Helix Solution pH 4 to 9 



° Helix Blood pH 1 8 2 1 20° i 



Limutus Blood* Buffer pH 7 52 



~~ 125" 



20 40 60 80 100 120 140 160 



Figure 1. Oxygen dissociation curves 

 of a salt free solution of haemocyanin 

 of the edible snail (Stedman and 

 Stedman 1 ), haemocyanin of the horse 

 shoe crab (Redfield and Ingalls 1 ) 

 and the blood of the snail ( Wolvekamp 

 and Kersten*). 



302 



