α-Helix unfolding in simple shear flow

Abstract

The unfolding dynamics of the α-helical poly-l-lysine (α-PLL) in Couette flow is reported. Real-time circular dichroism measurements for a range of molecular weights and shear rates have been made. The PLL molecules show a time- and shear rate-dependent unfolding in simple shear flow with a critical strain (tc) value of ∼105. This strain value is found to be independent of the chain-length of the α-helices. The extent of unfolding is less pronounced with increasing molecular weight (M) for a given strain, showing a linear dependence of the remaining helix, α, on M: α ≈ M. Furthermore, the helix content, α, is found to show a power law dependence with strain: α ≈ (t)-1/2. A shear-induced rapi..