The secondary structure evaluation of CT domain helix No4 suggests a structural shift of the peptide to β-sheet. 
a) CD spectra of the helix No4 peptide peptide at different pH values.  
b) Representative AFM image of nanofibrils formed by the helix No4 peptide when incubated at pH 3.1.


METHODS
a) Samples with concentrations of 59-65 µM (0.18-0.2 mg/ml) for the helix No4 peptide and 0.2 mg/ml for the full-length CT domain were used for the CD experiment. The peptides and CT domain were analyzed with a Chirascan CD spectrometer (Applied Photophysics) and a 1 mm quartz cuvette. The temperature was maintained at 20 °C. The wavelength scan range was 190−260 nm (1 nm steps), the bandwidth was 1 nm, and the time per point was 1 s, with triplicate measurements for each sample. Data was smoothed using Savitzky-Golay filter with 7 points of window. The deconvolution analysis of CT-domain in solution was performed using the BeStSel software.


b) 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
.csv text data
AFM image (as Bruker Nanosscope data .spm file and image .tif file)