Fig. 2: In vitro aggregation of signal peptide (SP-CoV2) of SARS-CoV-2 S protein.
From: Amyloidogenic proteins in the SARS-CoV and SARS-CoV-2 proteomes
a ThT fluorescence scan (λex 440 nm) shows a ~3-fold increase at λmax in presence of SP-CoV2 at 22 h. b Aggregation kinetics monitored using ThT fluorescence at 490 nm. Each dotted symbol represents the average value of two technical replicates and error bar represents the SEM of these replicates. The wine-coloured line shows the sigmoidal fitting of data points that determines the T50 of this reaction to be 2.84 ± 0.43 h. The aggregation kinetics shows a short lag phase that can be seen in the inset. c Secondary structural analysis of 0.25 mg/ml aggregates (240 h) using CD spectroscopy reveals two peaks having positive (202 nm) and negative ellipticities (218.7 nm), corresponding to the presence of β-sheet structures. The spectrum is smoothened with 10 points using the FFT filter function. d HR-TEM imaging reveals twisted fibrillar structures (100 nm scale bar) at 240 h (10 micrographs were captured from the same grid). e After 170 h incubation, SP-CoV2 fibrils appear branched through AFM (scale bar 400 nm). Seven micrographs were captured from the same sample. f Height profile of two fibrils shown with a green-coloured line in panel (e). Additional micrographs are given in Supplementary Fig. 2. The source data are given in the Source Data file. Arb. units are arbitrary units.
