Figure 2. Intrinsic tryptophan fluorescence was used to investigate the quenching and denaturation of transforming growth factor beta-induced protein (TGFBIp) A: Fluorescence traces of TGFBIp (0.1 mg/ml) in guanidine hydrochloride (GndHCl), ranging from 0 to 6 M, were shown. Samples were excited at 295 nm and scanned for the tryptophan emission. Inset: Fluorescence quenching experiments by acrylamide and KI. B: The emission maximum (E_max) and the intensity-averaged emission maximum (IAEM) were obtained by plotting the intrinsic tryptophan fluorescence traces versus GndHCl concentrations. Inset: Denaturation experiments by urea at various concentrations. Plot of the shift of emission maximum versus urea concentration clearly shows that urea fails to unfold TGFBIp, even up to 8 M. C: Thioflavin T (ThT) fluorescence intensity at 485 nm was used to determine the fibril formation of TGFBIp at various GndHCl concentrations (n=3, bar=S.D.).