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IMS develops new method for observing single proteins using infrared light


A research team, led by Assistant Professor Jun Nishida and Associate Professor Takashi Kumagai of the Institute for Molecular Science, has successfully observed a single protein and measured its infrared vibrational spectrum using infrared near-field optical microscopy light confined at the nanometer scale. This accomplishment is expected to be useful for chemical analyses. The results have been published online in Nano Letters.

(Left) Scheme of near-field infrared spectroscopy measuring a single protein.
(Right) The structure of the protein complex F1-ATPase and the subunit measured in this study.
Provided by Jun Nishida

Infrared light is extensively used in chemical analysis because it can measure vibrational spectra, which are also known as molecular fingerprints. Following the rapid development of nanotechnology in recent years, the demand for ultra-sensitive and super-resolution imaging using infrared light is increasing.

However, microscopy using conventional infrared light cannot measure samples of extremely small amounts or achieve nanometer-scale spatial resolution. Therefore, even with an infrared microscope, which is generally considered to have good sensitivity, it is usually necessary to measure more than a million proteins in the infrared spectrum, making it impossible to conduct measurements only on one protein.

The research group has now isolated the sub-unit comprising a protein complex called F1-ATPase on a gold substrate and measured it using near-field infrared spectroscopy in an ambient environment. From this they successfully obtained the infrared vibrational spectrum of a single protein.

The measurement methodology of single proteins is an important technique for clarifying the advanced functions of protein complexes and membrane proteins. In addition, a theoretical framework describing the interaction of proteins with a highly localized infrared near-field in nano-space was developed, and the signals obtained were successfully reproduced quantitatively.

Technological innovation is expected in ultra-sensitive and super-resolution imaging using infrared light and its application to various nanomaterials, including the chemical analysis of biomolecules.

Journal Information
Publication: Nano Letters
Title: Sub-Tip-Radius Near-Field Interactions in Nano-FTIR Vibrational Spectroscopy on Single Proteins
DOI: 10.1021/acs.nanolett.3c03479

This article has been translated by JST with permission from The Science News Ltd. ( Unauthorized reproduction of the article and photographs is prohibited.

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