The Aharon Katchalsky Memorial Lecture1

Abstract

AHARON KATZIR-KATCHALSKY was an outstanding scientist and humanist, whose objective contributions to our knowledge and understanding had long before his tragic death assured him a place in the top rank of this century. The world can ill afford to lose such minds.Not for this alone, however, is he being missed and mourned. After all, these of his contributions stand and will remain. He is being missed and mourned, by hundreds of people all over the world, for something much more personal and precious, something which each had received from him, at some encounter, at a seminar, at a public lecture, at a private discussion, something of the excitement and wonder of the intellectual pursuit which he could so magically arouse and instil.There was no occasion which Aharon Katzir failed to improve with his mind and words. Whenever he talked he aroused our intellectual curiosity, stimulated our thoughts, brought forth our interest. Activities which seemed commonplace, subjects apparently banal, he could make engage our minds. He left his audience refreshed, mentally invigorated, newly encouraged in their work, revitalized in their interest.It is Aharon Katzir who should have delivered the Plenary Lecture he anticipated to give today on biological membranes and biorheology. It is with many sad thoughts and in deep sorrow that I am speaking about his work in his place.Biorheology, movement and life had always fascinated him and the field stood close to the center of his research interests.While life is motion, the absence of motion-thermodynamic equilibrium-is death. The further we are from equilibrium, the younger we are, the more alive, the fuller of motion. Living processes should be far from equilibrium, they should override their environment, interact strongly with it, be in command. Biorheology deals with living processes, it deals with the fluid mechanical aspects of life. We could paraphrase biorheology as life, flow and deformation.In pursuing these aims the biorheologist tends to go in two directions. On the one hand, from a macroscopic point of view, he wants to understand the principles and forces which produce motion; on the other, from the microscopic point of view, he looks for interpretation in the molecular dynamics and structure of the system. This duality of approach was not always realised. The early chemists and biochemists who established the macromolecular, polymeric nature of most biological structural and chemically specific material did not at first see this as a world in motion. They were writing chemical formulas on their paper and for them these structures did not move.It was left to Werner Kuhn to establish and show that, conformationally, macromolecules 109