Helix No4 (peptide CT51-80) has been shown to form fibrils under acidic pH, as shown by AFM (right side). Glu is shown in red, Arg in blue, Cys in orange, and helix No4 in yellow. 


METHODS
The helix No4 peptide fibrils were imaged by means of AFM (Dimension FastScan microscope, Bruker) using Nanoscope Software (version 9.1, Bruker) and FastScan A probes (Bruker) operating under tapping mode. Samples were prepared by diluting a stock solution of fibrils (0.1 mg/ml, pH 3.1 and 2) between 10 to 1000 times in 1 mM HCl. 25 μL of the diluted samples were pipetted onto freshly cleaved mica and incubated for 10 min at room temperature. After incubation, aliquot excess was rinsed with filter-sterilized milli-Q water and dried using a stream of compressed air. Flattening of the height topology data and removing of the tilt and scanner bow were achieved using Nanoscope analysis software (Version 1.9, Bruker).


FILE FORMAT
AFM image (as Bruker Nanosope raw data .spm file and image .tif file
SEM image (.tif image file)