Single molecule secondary structure determination of proteins through infrared absorption nanospectroscopy

Francesco Simone Ruggeri,Benedetta Mannini,Tuomas P J Knowles,Roman Schmid,Michele Vendruscolo

doi:10.1038/s41467-020-16728-1

Francesco Simone Ruggeri, Benedetta Mannini + Show 3 more

Open Access

https://doi.org/10.1038/s41467-020-16728-1

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Journal: Nature Communications	Publication Date: Jun 10, 2020
Citations: 95	License type: open-access

Affiliation: University of Cambridge

Abstract

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.

Highlights

The chemical and structural properties of biomolecules determine their interactions, and their functions, in a wide variety of biochemical processes
On the other hand, infrared nanospectroscopy based on thermochemical detection (atomic force microscopy-infrared spectroscopy (AFM-IR)) measures directly the light absorbed by a sample by photothermal induced resonance[17,18]
The infrared absorption spectra produced are not affected by scattering effects or specific nanoscale selection rules, and as such they are in agreement with conventional bulk results[19,20,21,22,23,24,25,26]

Summary

Introduction

The chemical and structural properties of biomolecules determine their interactions, and their functions, in a wide variety of biochemical processes. 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. Current state-of-the-art nanoscale spectroscopy approaches offer remarkable sensitivity, but there is a tradeoff between sensitivity and ability to relate directly the acquired chemical information into quantitative characterisation of structural properties Scattering based methods such as tip-enhanced Raman spectroscopy (TERS)[8] and scanning near field optical microscopy (sSNOM)[9] have enabled the acquisition of chemical information on the nanoscale[10,11] and with single molecule and in some cases even single chemical bond scale[12,13]. The achievement of this high sensitivity enables the accurate determination of the secondary structure elements of single proteins in the amide band I region, such as α-helices and β-sheets, with similar accuracy than conventional bulk vibrational spectroscopy on samples with over a million-fold larger mass

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