Super-resolved FT-IR spectroscopy: Strategies, challenges, and opportunities for membrane biophysics

• Integration of SPM with FT-IR can enable super-resolved vibrational spectra.
• ATR-IR–SPM provides most flexibility in IR spectra acquisition.
• ANSIM has proven successful for super-resolved spectral mapping of protein fibrils.
• PTIR has clear potential for acquiring super-resolved spectra in cellular environments.

Direct correlation of molecular conformation with local structure is critical to studies of protein– and peptide–membrane interactions, particularly in the context of membrane-facilitated aggregation, and disruption or disordering. Infrared spectroscopy has long been a mainstay for determining molecular conformation, following folding dynamics, and characterizing reactions. While tremendous advances have been made in improving the spectral and temporal resolution of infrared spectroscopy, it has only been with the introduction of scanned-probe techniques that exploit the raster-scanning tip as either a source, scattering tool, or measurement probe that researchers have been able to obtain sub-diffraction limit IR spectra. This review will examine the history of correlated scanned-probe IR spectroscopies, from their inception to their use in studies of molecular aggregates, membrane domains, and cellular structures. The challenges and opportunities that these platforms present for examining dynamic phenomena will be discussed. This article is part of a Special Issue entitled: FTIR in membrane proteins and peptide studies.

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