Nano-Chemical Infrared Imaging of Membrane Proteins in Lipid Bilayers

By: Samuel Berweger, Duc M. Nguyen, Eric A. Muller, Hans A. Bechtel, Thomas T. Perkins, and Markus B. Raschke

J. Am. Chem. Soc. 135, 18292 (2013)

The spectroscopic characterization of bio-molecular structures requires nanometer spatial resolution and chemical specificity. We perform full spatio-spectral imaging of dried purple membrane patches purified from Halobacterium salinarum with infrared vibrational scattering-type scanning near-field optical microscopy (s-SNOM). Using near-field spectral phase contrast based on the Amide I resonance of the protein backbone, we identify the protein distribution with 20 nm spatial resolution and few-protein sensitivity. This demonstrates the general applicability of s-SNOM vibrational nano-spectroscopy, with potential extension to a wide range of biomolecular systems.