SUMMARY 447 



proteins to change their catalytic properties by the mere substitution 

 of one or another ligand in the five or six position is wholly unexampled 

 in the chemical literature; there are no models to account for it. There 

 are some brave people who, starting from models, have attempted to 

 derive a series of generalizations for the aid and comfort of the in- 

 vestigator who seeks to imagine what the ligand positions might be 

 that correspond to the potentials observed, and to the catalytic prop- 

 erty observed. Papers bearing on this are available in a bibliography 

 which I gave in my paper— particularly the considerations of J, P, R. 

 Williams, which were published about six months ago in the Biochem- 

 ical Journal. 



After a break for refreshments (which, I suspect, were sorely 

 needed!), we had the structure group. The question was: What is the 

 photochemical apparatus in bacteria? Now this never has been a ques- 

 tion in the green plants, even though I have a feeling that if you take 

 a similar collection of experts in the chloroplast field, you will find 

 divergences of opinion about what constitutes the photosynthetic ap- 

 paratus. In the case of the green plant, the question is how dirty must 

 it be before it satisfies the plant physiologist, and on the other hand, 

 how clean must it be before it satisfies the biochemist? The same 

 problem arises with the chromatophores, only at a level where you 

 can't see them in the microscope. At least the chloroplast people can 

 see what they are looking at and don't have to depend on fixation pro- 

 cedures. So they have arrived at their present state of disgrace, you 

 might call it, perhaps some twenty years before we are going to get 

 there, 



U I may make a small extrapolation, I suspect that in about ten 

 years we will have enough data to be arguing at the level that the 

 chloroplast people argue at now. This may be a dim prospect. But in 

 connection with it, in a rump session held last night (one of the two 

 rump sessions held and which lasted for the longest seven minutes on 

 record) there was a statement produced by Roger Stanier, speaking 

 for the assembled group, which I will read /;? extenso: "In every purple 

 bacterium"— I don't know why the green bacteria were left out, but 

 anyway— "In every purple bacterium, the photosynthetic pigments and 

 photochemical electron transport system are associated with the unit 

 membranes of the cell. The unit membrane, comprised of cytoplasmic 

 membrane, together with internal membrane, may take either vesicular 

 or lamellate form. In some cases, the internal vesicles are lamellate 

 and are physically continuous with the cytoplasmic membrane, but it 

 is not known how complete the continuity is between the cytoplasmic and 

 internal membrane systems, Photosynthetic pigments certainly are 

 present in the internal membrane, but it is not known whether they 

 are also present in the cytoplasmic membrane. The form and extent 

 of the internal membrane system, in any one species, can change in 

 response to environmental conditions during growth of a cell, so that 



