Biophysical Society Bulletin | February 2026

In Memoriam

Michael J. Saxton

Michael J. Saxton (1947–2025), a dedicated member of the Biophysical Society and the Membrane Structure & Function Subgroup, passed away on July 24, 2025. Mike received a Bachelor of Science in Chemistry from Michigan State University, a Master’s in Chem istry at the University of Oregon, and a PhD in Chemical Physics at Harvard University. After stints in the US Army and several academic institutions, Mike

unexpected byways in membrane biophysics. Michael Saxton was an unsung hero of biophysics. I think that he influenced the work of everyone who read his papers or talked with him.” Mike also made a major contribution to the scientific commu nity as a reviewer, a role for which he was disproportionally asked to serve. Many authors who at first would find his diffi cult questions and requests a nuisance that should be ignored later conceded that the meticulous reviewer was correct at every point. Even after his retirement, Mike made sure to attend the BPS Annual Meeting and to have something new to present each year. His preference was for the poster format for maximal interaction and modest exposure. During the poster sessions he would say that “participants alter their movements from random walks to form transient clusters,” alluding to his groundbreaking work on diffusion modes and their analysis. Mike’s “random walk” at BPS was, however, not at all random; it was guided by a long list of posters to visit and talks to attend. As Erin Sheets , professor at the University of Minneso ta, Duluth, recalled, “Mike was a strong supporter of so many of us, particularly when we were just starting out as young grad students, postdocs, and faculty, always taking the time to stop by our posters and presentations at the BPS Annual Meeting.” As a young scientist, Mike had an agreement with a junior colleague to meet up for dinner at the BPS Annual Meet ing unless someone very prominent made either of them a better offer. Lately, several of us had the honor and pleasure of being a standing dinner companion to him at the meeting. Characteristically, Mike did not recognize that he was by then a prominent person and a legend in his field. When he found out he was seriously ill, Mike did not think he would make it to the 2025 Annual Meeting. He was grate ful that he could attend, marking the 38th consecutive year he presented either a paper or a poster. His presence at the 2026 meeting and beyond will be sorely missed, but his ideas will continue to guide our thoughts, and his smile will always warm our hearts.

Michael J. Saxton

eventually settled at the University of California, Davis, where he worked as a research chemist until his retirement in 2008. Mike was well known for his contributions to our understand ing of complex diffusive behavior in biological systems. He developed computational models that bridged theoretical physics and experimental biophysics. His novel computational frameworks supported the interpretation of experimental data and provided predictive models. Indeed, the titles of many of his research papers posed important provocative questions and requests to experimentalists, such as “Wanted: Scalable Tracers for Diffusion.” Mike had a particular interest in modeling hindered and anomalous diffusion in biological systems, especially within crowded cellular environments like the plasma membrane, cytoplasm, and nucleus. Notably, he applied concepts from percolation theory and fractal geometry to explain subdiffu sive behavior, where the mean-square displacement grows slower than the expected linear relationship with time. His work integrated Monte Carlo simulations, Brownian dynam ics, and event-driven algorithms to explore how obstacles— both mobile and immobile—affect molecular motion. These models reveal how proteins navigate complex intracellular landscapes to find their interaction partners and thereby control the rate of biological processes. By using statistical tools to distinguish between normal, anomalous, directed, and confined diffusion, Mike’s work also provided some of the earliest frameworks for the analysis of single-particle tracking experiments. The impact of Mike’s work on the scientific community was far reaching. Michael Edidin , Professor Emeritus at Johns Hop kins University, reflected that “Michael’s theoretical papers were always challenging and stimulating to this experimen talist. In person it was a pleasure to talk with him, exploring

— Ingela Parmryd , University of Gothenburg — Thomas Jue , University of California, Davis — Anne Kenworthy , University of Virginia

February 2026

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