Infrared spectroscopy enables the investigation of conformational protein changes, associated with human diseases, such as Diabetes II or Alzheimer’s disease. However, the in-vitro investigation of individual molecules remains challenging, but could provide insight into mechanisms leading to structural changes. This is due to the lack of suitable light sources, among other things. Here, we detect polypeptide conformations at attomolar concentration within minutes, exploiting Fourier-transform infrared (FTIR) spectroscopy and the plasmonic enhancement of a single resonant nanoantenna, being enabled by using a highly brilliant, broadband mid-IR laser. We successfully determine polypeptide conformations and compare our results to Globar and synchrotron measurements.
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