New Insights from Sum Frequency Generation Vibrational Spectroscopy into the Interactions of Islet Amyloid Polypeptides with Lipid Membranes

Figure 7

Determination of the orientation of human IAPP aggregates at the lipid/water interface. (a) Definition of three orientation angles (, , ) for Euler transformation from the laboratory to the molecular frame. (b) psp (chiral) SFG spectrum of hIAPP aggregates in the amide I region. and denote the characteristic peaks for amide I symmetric and antisymmetric modes. (c) Scheme showing the divide-and-conquer method for simulations of the SFG spectra from calculations of hyperpolarizability derivatives with respect to normal mode displacements in human IAPP aggregates. (d) Relationship between the intensity ratio of the mode to the mode and orientation angle . The blue curve is obtained analytically from (1), and the red curve is obtained numerically. (e) Chiral SFG spectra of human IAPP aggregates simulated for various orientations at the interface. (f) Visualized orientation of the human IAPP aggregates at the lipid/aqueous interface. Adapted from [65] with permission. Copyright 2012 Elsevier.

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