Biophysical Society Bulletin | July/August 2021

InMemoriam

Katharina Gaus

outset of this significant legacy, when Gaus started the Cellular Membrane Biology Lab, she began by first applying the Laur- dan-GPmaps she had published in her 2003 PNAS paper to the study of focal adhesions and the T cell immunological synapse. In these experiments, she showed for the first time a ring of high membrane order at the synapse periphery which, importantly, prompted Gaus to seek imaging technology that would enable her to observe membrane receptor organization with super resolution. Thus, fromhere her lab played a prominent role in the application of newly developedmethods in single-molecule localizationmicroscopy (SMLM) to the study of the nanoscale organization of proteins in immune cells. She then showed how quantification of SMLMdata can be used to describe nanoscale clustering, followed by a string of high-impact discoveries that describe the nanoscale organzation of LAT and Lck, respec- tively, at the T cell immune synapse. Guas continued tomake advances inmembrane probes (including FRET sensors to probe membrane change and receptor clustering), image analysis, and surface chemistry, all with the aimof obtaining a better under- standing of the role molecular organization plays in regulating signalling. Finally, she made a major advance inmicroscopy hard- ware using an actively stabilizedmicroscope to achieve unprece- dented resolution. In parallel to this quest for understanding how T cells make decisions at the single molecule level, remarkably, Gaus built a research environment at UNSWequipped with state-of-the-art technology to foster quantitative imaging of biology and re- cruited a critical mass of biologists, physicists, and chemists to harness this technology, which collectively transformed single molecule science in Australia. In particular, by establishing both the UNSWBiomedical Imaging Facility and the EMBL node in Single Molecule Science—a center which today houses 12 group leaders focusing on providing a molecular perspective on complex biological systems—she generated a hub for single molecule and cellular biophysics within Australia that has launched the careers of several early andmid-career researchers who now run laboratories both locally (Sydney andMelbourne) and across the globe. In closing, while there is no denying that Gaus’s scientific contributions to the fields of microscopy and immunology are already immense, it is likely that the true reach of her contribution to science can only be assessed in the years to come, when the next generation of early career biophysicists she mentored with unlimited support begins to flourish andmaintain her research vision to quantify biology at the single molecule level. Thank you to Michelle Digman for initiating this piece as well as Dylan Owen and Jeremie Rossy for useful discussions.

Katharina Gaus (1972–2021), who recently passed away was an incredi- ble pioneer in super-resolvedmicros- copy of T cell membrane organization and an instigator for single molecule biophysics in Australia. Gaus trained, mentored, and inspired several early career researchers to research inde- pendence at the EMBL Australia node in Single Molecule Science at the Uni- versity of New SouthWales, Sydney (UNSW).

Katharina Gaus (Photo credit: Michael Gal)

Born in Germany and trained as a physicist at the University of Heidelberg, Kat completed her PhD on intracellular protein dy- namics at Cambridge University (1996–1999), and then relocated to Australia to undertake postdoctoral training in the lab of Wendy Jessup , who was embedded in the Sydney Heart Research Insti- tute and UNSW. While in Jessup’s lab, Gaus investigated environ- mentally sensitive dyes to study membrane lipidmicrodomains and at this time developed a keen interest for quantitative biology and fluorescence microscopy. Thus, in search of new imaging tools to quantify these membrane biosensors, she secured a series of competitive research fellowships (2001–2005) that enabled her to travel to the labs of Enrico Gratton in the United States (University of Illinois, Urbana-Champaign) and Kai Simons in Germany (Max Planck Institute for Cell Biology and Genetics, Dresden) andmaster the most cutting-edge biophysical methods available at the time to quantify cell membrane structure and dynamics. It was this highly informative experience that led to Gaus’s first landmark paper in Proceedings of the National Academy of Sciences (PNAS), in which together with Gratton she demon- strated the use of two-photonmicroscopy for imaging Laurdan with a per-pixel generalized polarization (GP) analysis to create membrane order maps, and ultimately her career-long dedication to the development of new super-resolved fluorescence micros- copy methodologies to examine the plasma membrane of intact living cells. At UNSW, Gaus forged a remarkable career as a National Health andMedical Research Council (NHRMC) fellow and UNSWScien- tia Professor. Here, she first established the Cellular Membrane Biology Lab (2005), then the Biomedical Imaging Facility (2009; a resource that today houses more than 40 of the most advanced fluorescence microscopes capable of STORM, PALM, STED, FLIM, and FCS), and finally the EMBL Australia node in Single Molecule Science (2014) that is part of the Australian Research Council (ARC) Centre of Excellence in AdvancedMolecular Imaging. At the

— Elizabeth Hinde — Enrico Gratton

July/August 2021

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