PHYCOERYTHRIN 249 



It may be remarked that most of the above opinions were 

 put forward before the work of Palladin on respiration and the 

 relationships between pigments and enzymic activity appeared. 

 And, in view of this, some of the earlier experiments appear to 

 require reconsideration from Palladin's point of view. 



PHYCOERYTHRIN. 



Phycoerythrin is a red pigment commonly occurring in red 

 sea-weeds, especially when growing in deep water. It has 

 recently been investigated by Hanson,* on whose account the 

 following description is based : — 



Phycoerythrin is easily soluble in water, giving a rose- 

 coloured solution which exhibits a well-marked orange fluor- 

 escence ; the spectrum shows that the chief absorption is that 

 of the blue-green rays. 



Preparation. 



To prepare a solution of phycoerythrin the red sea-weed, 

 Ceraniium rubrum, which is one of the best to use, is washed 

 in ordinary water to free it from sea salts and adhering sand. 

 It is then soaked in distilled water ; in two days most of the 

 pigment will have diffused out. The solution is filtered through 

 glass wool and a few drops of eucalyptus oil added as an anti- 

 septic, for putrefaction soon sets in. 



It is a matter of great difficulty to obtain a pure sample of 

 phycoerythrin, for, in an aqueous solution, it passes over into 

 an irreversible gel,f even when kept at o" C. This, of course, 

 renders ordinary filtration extraordinarily slow, and thus in- 

 creases the difficulty of purification. 



The solid phycoerythrin may be prepared from the aqueous 

 solution by concentrating it under reduced pressure at a 

 temperature not higher than 38° C. ; any precipitate which 

 comes down during this process must be filtered off. Methyl- 

 ated spirit is then added to the concentrated solution until 

 the fluorescence disappears. The precipitated phycoerythrin 

 is allowed to settle and the more or less clear supernatant 

 fluid is filtered off", again treated with alcohol, and filtered. 

 The operation is repeated until the red colour has entirely 

 disappeared from the solution. The precipitates are washed 



* Hanson : " New Phytologist," 1909, 8, 337. 

 t See Section viii, on Colloids. 



