Nanoscale structural mapping of protein aggregates in live cells modeling Huntington's disease by mid-infrared photothermal microscopy

Protein aggregation is associated with many neurodegenerative diseases. We applied mid-infrared photothermal (MIP) to dissect the secondary structure of protein aggregates in living yeast cells modeling Huntington's disease. We validated that MIP spectroscopy could reveal β-sheet enrichment by significant spectral changes and confirmed the β-sheet enrichment of aggregates in high throughput by wide-field fluorescence-detected MIP. By label-free identification of protein aggregates, we observed a further red shift in spectra for aggregates without GFP tag. Finally, by performing MIP spectroscopy with fine spatial steps, we discovered a partition of secondary structures between β-rich core and ɑ-rich shell of the aggregates.