Berlin 2024 – scientific programme

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BP: Fachverband Biologische Physik

BP 15: Poster IIb

BP 15.1: Poster

Tuesday, March 19, 2024, 18:00–20:30, Poster F

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, and •Alfred J. Weymouth — Universität Regensburg, Regensburg, Deutschland

Surface-layer (S-layer) proteins form the outermost envelope in many bacteria and most archaea and arrange in two-dimensional quasicrystalline 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 (sodium dodecyl sulfate, SDS), which are used to isolate the S-layer proteins from the cells. SDS was not visible in the TEM images, requiring 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.

J. Phys. Chem. B 127, 6949 (2023)

Keywords: Atomic force microscopy; s-layer; transmission electron microscopy