Seminars at the Franklin: Arjun Narayanan

24th July 2024, 12:00 – 1:00 pm


The Diverse Photophysics of Fluorescent Proteins


Fluorescent proteins (FPs) have been a revolutionary force in bioimaging. The discovery of the green fluorescent protein (GFP) dramatically enhanced our ability to image specific proteins in living systems in real time. GFP was quickly shown to have an array of stable mutants yielding emission tuneable across the visible spectrum, allowing the study of protein-protein interactions for example. The FPs were variously shown to undergo excited state proton transfer, excited state isomerization and permanent photochromic reactions. The latter two led to the practical application of super resolution bioimaging and the development of optical highlighter imaging respectively. All of these properties ultimately derive from the extraordinary diverse photophysics of the chromophore of GFP, HBDI.

In this presentation, the photophysics of HBDI will be reviewed, along with some of the methods of ultrafast spectroscopy employed in its study. We then describe how the protein matrix controls HBDI photophysics, leading to the diversity in FP behaviour. These measurements not only allow better understanding of – and control over – FP behaviour but also affords the opportunity to investigate protein structural relaxation dynamics away from equilibrium.


Arjun Narayanan is a condensed matter physicist specialising in the physical chemistry of living matter. His academic journey included work in nanoelectronics at the Tata Institute of Fundamental Research (M.Sc.) and solid-state physics at New York University (PhD) and Oxford University, where he contributed to the understanding of quasi 1-D organic superconductors and topological insulators. More recently, he has applied condensed matter physics concepts to study the unconventional physical chemistry of living cells and tissues, enhancing our understanding of cell biology aspects such as protein quality control and cytoskeletal self-organization. Following positions at Oxford University and MIT, he served as the ELBE Fellow at the Max Planck Institute for the Physics of Complex Systems in Germany. Currently, Arjun seeks to advance our knowledge of cell biology and non-equilibrium physics through the exploration of non-equilibrium self-organization in biological systems.