Interactions between amyloid proteins and membrane surfaces are important in triggering amyloid aggregation and instigating cytotoxicity. Here, we used chiral sum frequency generation (SFG) spectroscopy to probe the aggregation of human islet amyloid polypeptide (hIAPP) upon interactions with lipid molecules at the air-water interface. We used the chiral vibrational signatures of the amide I and N-H stretch of the peptide backbone and observed in real time the misfolding of hIAPP from disordered to alpha-helical and then parallel beta-sheet structures. Moreover, we used the ab initio method to calculate the hyperpolarizability of the hIAPP aggregate and applied the results to analyze its chiral SFG spectra. We found that the beta-strands inserted into the lipid surface at ~48 degree, providing insight into its structures at the interface. Our results demonstrate that chiral SFG is viable for studying molecular mechanism of amyloid aggregation in the early stages at membrane surfaces.

Early stages of amyloid aggregation of hIAPP on membrane surfaces probed by chiral sum frequency generation spectroscopy

245th National Meeting (2013)

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