Fluorescent molecules could throw light on Alzheimer’s

– Manauv Vyas Hemakumar

Image: Debasish Giri

Fluorescent Molecular Rotors (FMRs) are synthetic molecules that are dim when they can freely spin but emit bright fluorescence when their rotation is hindered by binding to another molecule or due to the viscosity of the surrounding medium. This exciting ability is already being used to study conformations of protein aggregates and to measure microviscosity – an important parameter in cellular environments. A significant deviation from the norm usually spells biological trouble.

The sensitivity of FMRs as viscosity probes is restricted by the contrast in fluorescence intensity they can display over the range of viscosity values. Currently used FMRs work over a very narrow viscosity range. To improve their sensitivity, Govindasamy Mugesh and his team from the Department of Inorganic and Physical Chemistry designed novel variants of these compounds. They substituted an oxygen atom in the chromone core of the molecules with chemically similar but heavier atoms like sulphur, selenium and tellurium, one at a time, and studied how this influenced FMR properties.

Through a series of experiments, they deduced that the selenium-substituted FMR exhibited appreciable fluorescence contrast over the widest range of viscosity changes, making it the most sensitive viscosity probe. Interestingly, all the variants were selectively sensitive to protein aggregates of amyloid-β fibrils, which form plaque deposits in the brains of Alzheimer’s patients. The sulphur variant emitted light of the highest wavelength, conferring additional practical advantages. Such probes pave the way for further research in diagnostics and progression of diseases like Alzheimer’s.

REFERENCE:
Giri D, Chauhan E, Mugesh G, Chalcogen-Substituted molecular rotors as polarity and viscosity sensors for amyloid-β fibril formation and bioimaging, Chemistry (2026).
https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202503195

LAB WEBSITE:
https://www.mugesh-iisc.in/