By Piotr Fajer
Don and Structural Biology
Don coined the term Structural Biology. He is co-author of Caspar and Klug quasi-equivalence theory of virus structure according to which the proteins making a viral coat are capable of undergoing structural changes in order to make different bonding patterns with each other. This was revolutionary as the accepted view then was that coat proteins are identical bricks making identical bonds with each other. Now, it is widely accepted that the structural plasticity of proteins brought upon the small movements of the atoms making the proteins underpins the complexity and variety of ordered structures, allows changing shapes of proteins to be a switching mechanism reporting on presence of various signals, activation of enzymatic reactions or ability to do mechanical work.
Don’s Legacy at IMB/FSU
Don’s arrival at FSU put IMB/FSU instantly on the map in the field of structure determination. The Structural Biology program in the Institute of Molecular Biophysics (IMB) was in its infancy, we had just hired three Assistant Professors and the Director, Prof. Lee Makowski, a former graduate student of Don Caspar. Somehow, Lee persuaded Don to come for a sabbatical. Don loved it and moved to Tallahassee. That same year Don was elected to the National Academy of Science, having Don in the Institute made our recruitment of next faculty so much easier. Don’s presence was a key factor in the Institute obtaining a National Science Foundation Research Training grant, the grant that provided us with fellowships for graduate students and postdoctoral associates. One of these researchers stayed on at FSU and is now an FSU Distinguished Research Professor, Prof. Richard Bertram. Don’s tireless championing of cryo-electron microscopy as a structure determination tool helped us attract Prof. Ken Taylor (another FSU Distinguished Research Professor) from Duke University, who in turn made the Institute a powerhouse in electron microscopy. Five out of 9 members of the Institute utilize electron microscopy as their main research tool. This was very much a result of Don’s original vision.
Guiding hand and feminist
For a lot of us he was an ultimate father figure. As large as his scientific achievements were, his humanity was even bigger. Not a hurrah cheerleader, Don was a steady guiding hand, ready to offer praise or simply offering no comment, which was the comment. At his 90th birthday Symposium, which attracted 15 members of National Academy of Sciences, 4 Fellows of Royal Society and two Nobel Prize winners all coming on their own dime to Tallahassee to honor Don, the common thread was, “Don was inspiration and mentor for me.” One of those notables quipped, “There is nobody else in this room who would attract so many colleagues to a Symposium honoring them”. Two very successful women scientists reminisced how Don’s support when they were graduate students and postdocs was instrumental, inspirational for their careers in Academia. Dare I say, Don was a feminist, since his early days of working with Rosalind Franklin of DNA fame, establishing the first Structural Biology Institute with two women scientists, Carolyn Cohen and Susan Lowey, to his biased selections of the Caspar Lectures (6 out of 8 were women) , Don was always a champion of women scientists.
Don as a friend
Following the death of his wife, Don returned to Tallahassee. Prior to the pandemic, he would come to the Institute every day. He would do his own research but he would also spend hours discussing the newest paper with whomever he would corner. To see how his brain worked, to see his scientific curiosity was awe-inspiring. During this time, Don became a personal friend with whom I could bounce off ideas, ask for advice or simply enjoy his presence and walks on the Saint George Island beach. As one of my colleagues stated: “we were incredibly lucky to know and interact with Don”. He will be missed!