Single molecule secondary structure determination of proteins through infrared absorption nanospectroscopy

• Published in: Nature communications 2020-06, Vol.11 (1), p.2945-2945, Article 2945
• Main Authors: Ruggeri, Francesco Simone, Mannini, Benedetta, Schmid, Roman, Vendruscolo, Michele, Knowles, Tuomas P. J.
• Format: Article
• Language: English
• Subjects: 132/122; 140/125; 147/3; 631/57/2265; 631/57/2272/2273; 631/57/2282; 639/638/11/2257; 639/638/440/56; Absorption; Absorption spectra; Biomolecules; Biophysics; Humanities and Social Sciences; Infrared absorption; Infrared spectra; Molecular Conformation; Molecular structure; multidisciplinary; Nanotechnology - methods; Protein folding; Protein structure; Proteins; Resonance; Science; Science (multidisciplinary); Secondary structure; Signal to noise ratio; Spectrophotometry, Infrared - methods; Spectroscopy; Spectrum analysis
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-16728-1

The chemical and structural properties of biomolecules determine their interactions, and thus their functions, in a wide variety of biochemical processes. Innovative imaging methods have been developed to characterise biomolecular structures down to the angstrom level. However, acquiring vibrational absorption spectra at the single molecule level, a benchmark for bulk sample characterization, has remained elusive. Here, we introduce off-resonance, low power and short pulse infrared nanospectroscopy (ORS-nanoIR) to allow the acquisition of infrared absorption spectra and chemical maps at the single molecule level, at high throughput on a second timescale and with a high signal-to-noise ratio (~10–20). This high sensitivity enables the accurate determination of the secondary structure of single protein molecules with over a million-fold lower mass than conventional bulk vibrational spectroscopy. These results pave the way to probe directly the chemical and structural properties of individual biomolecules, as well as their interactions, in a broad range of chemical and biological systems. While infrared nanospectroscopy methods based on thermomechanical detection (AFM-IR) enables the acquisition of absorption spectra at the nanoscale, single molecule detection has not been possible so far. Here, the authors present off-resonance, low power and short pulse infrared nanospectroscopy (ORS-nanoIR), which allows measuring infrared absorption spectra at the single molecule level in a time scale of seconds with high throughput and demonstrate that the secondary structure of single protein molecules can be determined with this method.