Imaging of Protein Monomers and Polymers

For imaging fg monomers and soluble polymers, adsorption to polystyrene (PS) and to trioctylmethylamine (TOMA) coated silica wafers was used and imaging was carried out by topographic and lateral atomic force microscopy (AFM) scanning as described (Koo et al. 2010 (link); Galanakis et al. 2021 (link)). For enhanced image resolution, a modified graphite (MG) surface (water droplet angle 45.5° ± 0.5°, n = 3) was used as described (Protopopova et al. 2014 ) Briefly, a 2-μl aliquot of fg 5 μg/ml solution was applied for 5–15 s, immediately diluted with 100 μl deionized water for 10 s, dried by forced air, and scanned by AFM in tapping mode using super-sharpened cantilevers, SSS-SEIHR (Nanosensors, Germany) with a tip radius < 0.5 nm, and the MFP-3D AFM microscope (Asylum Research, Oxford Instruments, USA).