THE NATURAL STATE OF PllOTOCHLOROPHYLL 473 



you maj' still have a linkage between the pigment and the protein, or whatever it is 

 linked to, without having the complex functionally active. The complete pig- 

 ment may still be present. But our protochlorophyll holochrome certainly is 

 physiologically active in respect to this particular reaction, namely, its photo- 

 transformation to chlorophyll holochrome. 



Lumry: There appears to be a simple picture in your ultracentrifuge studies in 

 that the preparative technique does not result in a heterogeneous collection of 

 fragments of different sizes but rather a monodisperse material of some constant 

 intrinsic molecular weight. 



James Smith : I think that is true and that is Kupke's interpretation. He has 

 said that he would never have e.xpected to have seen the sharp ultracentrifuge 

 pictures and consistent S20 values that we have from such preparations if the 

 material were not a fairly homogeneous substance. 



Lumry: But remember Emil Smith's detergent^suspended fragments. 



James Smith: Detergent-suspended protochlorophyll holochrome will not trans- 

 form. We have tried many detergents. 



Lumry : I know E. Smith's material was beautifully monodisperse with a rather 

 low molecular weight. 



James Smith: That may be so. {Xote added in proof: There is no doubt that 

 with many dispersing agents a great many proteins and structural elements con- 

 taining proteins will yield smaller monodisperse components even though the 

 starting material is very heterogeneous in size. But this treatment very often 

 causes irreversible denaturation and to my knowledge Emil Smith never claimed 

 that his material possessed physiological activity.) 



Amon: I think this is a very important contribution that we have just heaid, 

 because it throws considerable light on the possibility of coordinating this ob- 

 servation with those on the protoplastids which Professors Strugger and Frey- 

 Wyssling have shown to be the precursors of chlorophyll-containing chloroplasts. 

 I take it that you ruled out the possibility that you are merely breaking chloro- 

 plasts or larger particles that have not transformed. If this could be coordinated 

 with the physiological picture then you would have a very good idea of just how 

 structural chloroplasts are formed. 



James Smith: Of course, to say that you have completely ruled out small or- 

 ganized particles, I suppose, is impossible. But we have filtered the solutions 

 through a Millipore Filter, the finest filter we can get, one which passes particles 

 less than 0.4 m- This material passes through the filter. This particle is not a big 

 one. I believe it is smaller than a granum. 



(_Note added in proof: Since this paper was presented at the Gatlinburg Confer- 

 ence, we have obtained lyophilized preparations of the active protochlorophyll 

 holochrome. These preparations are slightly yellow and are readily soluble in 

 water. They retain their ability, at least for several months, to form chlorophyll-o 

 holochrome when they are illuminated either in the solid state or in solution.) 



