INTERACTION OF ORGANIC MOLECULES WITH PROTEINS 115 



the dyes (Fig. 2a). Let us say curve (a) represents the binding in water. In 

 dioxane, as I said, you decrease the dielectric constant, so there would be a drop 

 in binding due to increased repulsion and there might also be competition. So 

 with dioxane you expect something like curve (c) and that is what you get. 



What would we expect with glycine? With glycine we increase the dielectric 

 constant, there is less repulsion, so you would expect an increase in binding, 

 and if there is any competition then binding ought to drop down. 



The figure shows that there is an increase in binding, that binding really 

 goes up. However, you could still claim, I think quite rightly, that maybe it 

 would have been way up above curve (b) though, and that it is perhaps down to 

 (b) because there is still some competition bringing it down. 



First we and several others have tried to measure the binding of glycine and 

 other amino acids and we can not find any. Secondly, I did bring in the point 

 in my talk that there seemed to be a linear relation in AF of binding. If there 

 were competition, I would not have expected that to be because the linear rela- 

 tion was a simple relation for the free energy dependence on dielectric constant 

 only. 



