Fig 1.
CD spectra of wild-type Aβ40 and Arctic Aβ40 variant in 100 mM SDS solution.
(A) Superimposition of CD spectra of Aβ40(L17A/F19A) (light grey) and wild-type Aβ40 (black) in 100 mM SDS solution. (B) Superimposition of CD spectra of Aβ40(L17A/F19A/E22G) (light grey) and Aβ40(E22G) (black) in 100 mM SDS solution.
Table 1.
The secondary structure contents estimated from the CD spectra of Aβ peptides.
Fig 2.
Comparison of the 2D 1H-15N-HSQC spectra of wild-type Aβ40 and Aβ40(L17A/F19A).
(A) 2D 1H-15N-HSQC spectrum of Aβ40(L17A/F19A) in 100 mM SDS solution. (B) Superimposition of 2D 1H-15N-HSQC spectra of Aβ40(L17A/F19A) (black) and wild-type Aβ40 (light grey) in 100 mM SDS solution. Residues with noticeable chemical shift changes were labeled. (C) The effect of L17A/F19A replacements on the backbone amide resonances of wild-type Aβ40. The weighted chemical shift differences ([(HNΔppm)2+ (NΔppm/10)2]1/2) were plotted as a function of residue number. HNΔppm and NΔppm were the 1HN and 15N chemical shift differences between wild-type Aβ40 and Aβ40(L17A/F19A), respectively.
Fig 3.
Comparison of the 2D 1H-15N-HSQC spectra of Aβ40(E22G) and Aβ40(L17A/F19A/E22G).
(A) 2D 1H-15N-HSQC spectrum of Aβ40(L17A/F19A/E22G) in 100 mM SDS solution. (B) Superimposition of 2D 1H-15N-HSQC spectra of Aβ40(L17A/F19A/E22G) (black) and Aβ40(E22G) (light grey) in 100 mM SDS solution. Residues with noticeable chemical shift changes were labeled. (C) The effect of L17A/F19A replacements on the backbone resonances of Aβ40(E22G). The weighted chemical shift differences ([(HNΔppm)2+(NΔppm/10)2]1/2) were plotted as a function of residue number. HNΔppm and NΔppm were the 1HN and 15N chemical shift differences between Aβ40(E22G) and Aβ40(L17A/F19A/E22G), respectively.
Fig 4.
Comparison of 13Cα secondary chemical shifts of double Ala-substituted Aβ peptides and their native forms.
(A) The plots of 13Cα secondary chemical shifts of Aβ40(L17A/F19A) (light grey) and wild-type Aβ40 (black) as a function of residue. (B) The plots of 13Cα secondary chemical shifts of Aβ40(L17A/F19A/E22G) (light grey) and Aβ40(E22G) (black) as a function of residue.
Fig 5.
The predicted secondary structures of the α/β-discordant segments of double Ala-substituted Aβ peptides and their native forms.
The secondary structure (upper row) for each amino acid residue was obtained by using the propensity-based prediction as described in Fig 2 caption of ref. 27. Adopting the notation used in Fig 2 caption of ref. 27, we denote the β-strands predicted with high and low probability by the symbols E and e, respectively. The symbols H and h were used for denoting the α-helical structures predicted with high and low probability, respectively.