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arXiv · 2307.07052

A Next-Generation qPlus-Sensor-Based AFM Setup: Resolving Archaeal S-layer Protein Structures in Air and Liquid

Theresa Seeholzer·Daniela Tarau·Lea Hollendonner·Andrea Auer·Reinhard Rachel·Dina Grohmann·Franz J. Giessibl·Alfred J. Weymouth
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Abstract

Surface-layer (S-layer) proteins form the outermost envelope in many bacteria and most archaea and arrange in 2D quasi-crystalline structures via self-assembly. We investigated S-layer proteins extracted from the archaeon Pyrobaculum aerophilium with a qPlus sensor-based atomic force microscope (AFM) in both liquid and ambient conditions and compared it to transmission electron microscopy (TEM) images under vacuum conditions. For AFM scanning, a next-generation liquid cell and a new protocol for creating long and sharp sapphire tips was introduced. Initial AFM images showed only layers of residual detergent molecules (SDS), which are used to isolate the S-layer proteins from the cells. SDS was not visible in the TEM images, requiring a more thorough sample preparation for AFM measurements. These improvements allowed us to resolve the crystal-like structure of the S-layer samples with frequency-modulation AFM in both air and liquid.

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Theresa Seeholzer, Daniela Tarau, Lea Hollendonner, Andrea Auer, Reinhard Rachel, Dina Grohmann, Franz J. Giessibl, Alfred J. Weymouth. 2023-07-13. A Next-Generation qPlus-Sensor-Based AFM Setup: Resolving Archaeal S-layer Protein Structures in Air and Liquid. https://doi.org/10.1021/acs.jpcb.3c02875

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