KATCHALSKI-KATZIR, T h e W e i z m a n n Institute of
Science, Rehovot , Israel I am most obliged to my colleagues for inviting me to give the closing lecture of the Symposium. I assume this choice was made because of my active involvement in the first two symposia on peptides, polypeptides, and proteins: the first, in 1961 in the United States, in Wisconsin,l and the second, in 1974 at Ayelet Hashachar, Israel.2 This week we have heard a number of interesting papers, and the discussion has been enlightening and often stimulating. As an old-timer in this field, I have had the pleasure of following its progress for more than 20 years. Moreover, as President of the State of Israel, I had time during my five years in that office to stand back and survey the achievements of my own group and that of other workers.
My own interest in synthetic high-molecular-weight polypeptides, the polyamino acids, started in 1946-1947. While studying biology a t the Hebrew University on Mount Scopus, I became very interested in biopolymers and decided to pursue my doctoral studies under the late Professor Max Frankel, then head of the Department of Theoretical Organic Chemistry and Polymer Chemistry. My late brother was working in that department as a young assistant, and it was a great joy for us to study together and pore through the works of Flory, Mark, Meyer, and others. Both Aharon and I were fascinated by theoretical and practical achievements in polymer chemistry and soon became known as the local experts in the field. This was not difficult because, at that time, no one else in Israel was involved with large molecules.
I wanted to choose a thesis topic that would be related to both polymer chemistry and biology, and I concentrated on the synthesis of polymers of amino acids and the study of their properties. I felt sure that these synthetic homopolymers and copolymers would represent simple model compounds that could be useful as tools in the study of native proteins, and hoped to find that under appropriate conditions, some of these polymers would behave as random coils in solution, as polyelectrolytes, or as macromolecules with well-organized three-dimensional structures. I expected to discover that some of the model polyamino acids would show interesting biological properties-that they would be cleaved by enzymes, for example, or show certain antigenic characteristics.
My initial attempts to synthesize high-molecular-weight amino acid polymers by the polycondensation of amino acid and peptide esters yielded only peptides with relatively-low-average molecular weights. I therefore