Prof. Roy S. Caplan

1927-2021

The Department of Biomolecular Science mourns the death of Professor Emeritus Roy Caplan at the age of almost 94. Roy was a renowned biophysicist in the field of bioenergetics, expert in mathematical modeling of molecular machines and biological oscillations.

Roy was born in 1927 in London. He grew up and educated in South Africa, receiving his B.Sc. (Cum Laude) in 1950 in chemical engineering from the University of the Witwatersrand in Johannesburg, and Ph.D. in 1953 from the same university for studying physical chemistry of macromolecules in solution. He then worked at the National Chemical Laboratory in Teddington, England until 1959, when he moved for two years to the NIH as a visiting scientist. As of 1961 he spent 4 years in the lab of Aharon Katzir at the Weizmann Institute, and then moved to Harvard Medical School in Boston as an Associate Professor of Biophysics (1969-1973). Following a Sabbatical leave at the Weizmann Institute (1971-1972), he immigrated to Israel and became an associate professor at the Weizmann Institute as of 1973. In 1977 he became a full professor. Subsequent to the foundation of the Department of Membrane Research by Ora Kedem, Roy succeeded her as departmental chair (1976-1979). He chaired the department again in 1984-1987. In 1996 he became a Professor Emeritus but continued to be scientifically active.

His studies at the Weizmann Institute were first focused on energy conversion processes and systems, with an emphasis on membrane transport. He, together with Ora Kedem and Aharon Katzir, developed a new approach to such systems — non-equilibrium thermodynamics. As of the mid-seventies, his group started to study (in addition to thermodynamics of transport processes through biological membranes) the properties, kinetics, and proton-pump activity of bacteriorhodopsin in the purple membrane of archaea (wrongly considered then as halobacteria). These were the first years of studying bacteriorhodopsin and his group published ample of papers in leading journals about this. When Roy approached retirement, he mainly focused on mathematical modeling of molecular machines. These included, among many others, microscopic reversibility in enzyme kinetics, electrochemical potential, and the mechanism of rotation of the flagellar motor.

Roy was loved by his acquaintances because, in addition to being a superb and very clever scientist, he was a descent and modest person, humane, a knowledgeable conversation man, and a very dear individual. May his memory be blessed.