774 Editor: E. HEINZ 
osmotic effects, nor do I see dramatic evidence for binding in Dr. ABRAMS experiments. Ifthe osmotic 
effect is equivalent to the amount of molecules accumulated, how could you explain this otherwise 
than by assuming that these molecules are free, because the activity of water outside the cell can 
be considered as rather constant. If water goes into the cell there must be something which de- 
creases the activity of the water inside, and how could we explain this by simple binding in an 
undissociated form ? 
BrittEN: I don’t think that from our point of view it is necessary to say that, for instance, the 
sucrose in Dr. ABRAMS’ system is bound. It might very well be in free solution. We, in fact, have never 
taken the position that all of these phenomena can be explained on the basis of binding, and I 
think it is quite clear that there are osmotic constituents in free solution in the cell. 
I would like to discuss for a moment some observations on pools of uracil compounds formed 
with labeled “C-uracil by E. colz. These observations have made clear to me some novel properties 
of the pool in E. colt. 
The first observations were preparato1y to studies of RNA synthesis and we got into the pool 
Glucose 
0.8 L 



K Chloride 
2 
o 
K Formate 
ABSORBANCY 
©) 
pn 
2 
N 
25 50 TES) 
MINUTES 
Fig. 4. The effect of glycolysis on protoplasts stabilized with 0.2 M K formate and 0.2 MW K 
chloride. Protoplasts of S. faecalis were stabilized in solutions of K-formate (0.2 M@) and KCl 
(0.2 M), each containing 0.075 MM K-phosphate, pH 7.2. Glucose (0.01 MW) was added to both 
suspensions at the time shown by the arrow. The rate of swelling observed photometrically 
indicates that the rate of penetration of K formate during glycolysis becomes very rapid while 
the rate of penetration of KCl remains unchanged. The initial rates of glycolysis in both cases 
are the same. 
3000 + 



—— Total cell 
2000 
1000 


! I Ea 
| 2 3 4 2) 6 

Radioactivity incorporated counts /min 
Time in minutes 
Fig. 5. Incorporation of [!4C]-uracil into the metabolic pool and the RNA of E. coli ML-30, per mg 
(wet)/ml. The difference between the two curves is the radioactivity in the metabolic pool. 
Initial uracil concentration was 10-7 MM. Temperature: 37°. 
References p. 777 
