Earl W. Prohofsky

After 48 years of dedicated service to Purdue University and six short years of retirement in Florida, Earl. W. Prohofsky passed away on 22 September 2019 in Sarasota. Earl came to the Purdue department of physics with his wife Sue in 1966, after earning a PhD from Cornell University in condensed-matter physics under renowned theorist James Krumhansl and a stint at the Sperry Rand Research Center. Originally he was interested in the connection between vibrations and many-body electron behavior in traditional insulators and semiconductors, but after a few years, Earl turned his attention to the vibrational properties of amino acids, proteins, and DNA, which would remain his unique focus through the rest of his career.

At a time when it seemed that few physicists knew the difference between a protein and a proton, Earl put Purdue’s physics department on the map for the new field of “biological physics” by introducing new mathematical and computational techniques for tackling those complex systems. He began by considering simple chains of identical amino acids, in the manner that physicists tend to simplify problems, but quickly worked his way up to real biological macromolecules. By the mid 1970s he was working closely with Purdue colleague Lonnie Van Zandt, who passed away in 1995, and his and Zandt’s students to calculate the vibrational modes of DNA and RNA using Green function refinement techniques, which led to years of effort toward understanding the physics of the double helix.

Computers were not yet powerful enough to support molecular dynamics simulation of a short DNA stand beyond the 10 picosecond range, but Earl provided an alternative computational technique, based on his vibrational mode analysis method, for investigating complex problems such as the thermal fluctuational base pair opening dynamics of a DNA replication fork in the microsecond range. His investigation led to the conclusion that thermal fluctuational base pair opening may facilitate the helicase enzyme unwinding of a replicating DNA. Soon after his publication in 1992 , biologists found supporting evidence in 1993 and in later reports. The ring-shaped helicase enzymes were found to unwind DNA/RNA hybrids and DNA replication forks by thermally induced or passive mechanisms.

Throughout Earl worked to strengthen the field of biological physics, serving as secretary/treasurer of the Division of Biological Physics at the American Physical Society. He wrote the reference book Statistical Mechanics and Stability of Macromolecules (1995), he claimed, in order to avoid having to repeatedly explain the basic concepts to various referees. In large part due to his efforts, Purdue now has one of the larger biological physics groups in the US.

In addition to his dedication to research and teaching at Purdue, Earl was also involved for many years with the annual Holocaust Remembrance Conferences sponsored by the Purdue Hillel Foundation. Earl is survived by his wife Sue, four children, and eleven grandchildren. He is deeply missed by his friends, family, and colleagues.