Single-protein infrared vibrational spectroscopy (left) Schematic of near-field infrared spectroscopy measuring a single protein. (Right) The structure of the F1-ATPase protein complex and the subunit measured in this study. Credit: Jun Nishida
An interdisciplinary research team, led by Assistant Professor Jun Nishida and Associate Professor Takashi Kumagai of the Institute of Molecular Sciences, successfully observed the vibrational spectra of single proteins, consisting of approximately 500 amino acid residues, in using advanced measurement techniques based on field optical microscopy. This method uses light confined to the nanoscale, enabling detailed analysis of extremely small samples, which previously represented a challenge with conventional infrared spectroscopy.
The study is published in the journal Nano letters.
Conventional infrared spectroscopy has been widely used for structural and chemical analysis of various materials because it can measure vibrational spectra, often called “molecular fingerprints.”
This new achievement represents a major advance toward technological innovations such as ultra-sensitive and super-resolution infrared imaging, as well as single-molecule vibrational spectroscopy.
The rapid development of nanotechnology in recent years has led to an increasing demand for ultra-high sensitivity and super-resolution infrared imaging. However, conventional infrared spectroscopy is limited in measuring extremely small samples or achieving nanoscale spatial resolution. For example, even infrared microspectroscopy with good sensitivity requires more than a million proteins to obtain an infrared spectrum, making it impossible to measure a single protein.
In their study, the research team isolated a single protein, a subunit comprising a protein complex called F.1-ATPase, on a gold substrate and performed near-field infrared spectroscopy measurements in an ambient environment.
They successfully acquired the infrared vibrational spectrum of a single protein, representing a major advance that could lead to the characterization of the local structural organizations of individual proteins. This information is particularly important for understanding the sophisticated functions of protein complexes and membrane proteins, providing a deeper understanding of their mechanisms and interactions.
Furthermore, they developed a new theoretical framework describing nanoscale interactions between the near-infrared field and proteins.
Based on this theory, the team was able to quantitatively reproduce the observed experimental vibrational spectra. These results will be invaluable for the chemical analysis of biomolecules as well as various nanomaterials, paving the way for a range of infrared spectroscopy applications at the nanoscale.
More information:
Jun Nishida et al, Sub-tip-radius near-field interactions in nano-FTIR vibrational spectroscopy on single proteins, Nano letters (2024). DOI: 10.1021/acs.nanolett.3c03479
Provided by the National Institutes of Natural Sciences
Quote: Research team reports observing vibrational spectra of a single protein by infrared nanospectroscopy (January 10, 2024) retrieved January 10, 2024 from
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