Figure 5. Conformation and surfactant properties of CSR species generated from T40 by IDE.

(A) and (B) T40/IDE digestion triggers a switch to β-structure. T40 CD spectra (250 to 190 nm) before and after addition of IDE (A) and percentage of secondary structures (B). (C) CSR species are surface-active. T40/IDE digest (30 min) was subjected to RP-HPLC. Peaks (a–k, as annotated in the inset) were lyophilized, re-suspended in 200 mM sodium acetate pH 3 and surface tension measured before and after neutralization (1M NaH₂PO₄, pH7.2). Surface tension calculations were as described in Methods. ‘*’ p<0.05, and ‘**’ p<0.007.