I had also worked on electrolytes... on electrolyte theory. And I remember my first visit to the United States was also in 1954 when I came to a birthday party of Peter Debye which was arranged at Yale University by Lars Onsager and his colleagues. And...

[Q] What birthday of Peter Debye?

Peter Debye was 70 years old that time. And he took me away and said, 'Give up the work on electrolyte theory, the first approximation has been done...',  namely by himself and Hückel, and he said, 'Don't try higher approximations, go on with your fast reaction work, that's really something new'. And so we became very good friends. Later he invited me to Cornell University, I became a Professor at Large at Cornell University, I gave lecture series there, so this opened a very nice contact. Also with Lars Onsager, as you know yourself we often visited him and worked together.

So I should say perhaps a word about you. It was again a conference on coordination chemistry, the so-called ICCC, International Conference on Coordination Chemistry, at Vienna in 1964, and I think you worked with Professor Gutmann there, so you were in the meeting office and I came a little late...

[Q] As always...

... and so I was nicely welcomed by you. And that's also when I asked you why don't you come to Göttingen to do a thesis with me, and you came to Göttingen, and again we thought at that time already a little bit about biological reactions, we thought of measuring complexes between ATP, adenosine triphosphate, one of the most important energy sources in living cells, and magnesium and calcium because those reactions usually require either magnesium or calcium ion to proceed. But at the same time Max Delbrück visited us, remember, and he brought along a molecule and say, 'Why are you studying those boring molecules, I have something which is much more interesting', and that was one these cage molecules. I think it was monactin and dinactin.

[Q] Monactin.

I am mentioning these because this is a molecule which completely surrounds the ion, so in order for the molecule to react with the sodium or potassium it can specifically distinguish between two chemically very similar ions, the potassium and the sodium ions, but it can distinguish by orders of magnitude. And in order to do so it has to completely wrap around the ion, in other words substitute all the water molecules from the inner shell, which if you look for the hydration, heat, this is some 100 kilo calorie.  And so one starts to wonder how could that be a fast reaction? And apparently it does it again. It brings in one ligand, substitutes water molecule, brings in the next ligand, and it does the whole thing within 10^-8 to 10^-9 seconds. So this is really one of the... again of the very rapid coordination reactions there. Now you studied then other substances like, I think from mushroom, from Amanita?

[Q] But they were all of the kind of these, sorting 'caging' the molecule to be selected.

Yes, and that's a trick to completely engulf the ion so that all water molecules are substituted and then the difference in the solvation energy, in the hydration energy, between sodium and potassium, sodium is a smaller ion, can be become effective and that's a very important reaction. Now a nerve membrane you need a rapid exchange of sodium and potassium and those substances called membrane carriers are involved.