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4/4 - Seminar (chemical biology): Elsa Yan, Yale

Elsa Yan - speaker's webpage
Department of Chemistry

Characterization of protein secondary structures at interfaces using chiral sum frequency generation spectroscopy

Characterization of protein secondary structures using vibrational spectroscopy is challenging because of strong vibrational backgrounds from water and spectral overlapping of proteins’ vibrational bands. Our recent studies have shown that chiral sum frequency generation (cSFG) spectroscopy can be used to address the challenge. We found that cSFG spectra of the amide I and N-H stretch of protein backbones provide highly characteristic vibrational signatures to distinguish parallel beta-sheets, anti-parallel beta-sheets, alpha-helices, 3-10 helices, and random-coils at interfaces. Because cSFG spectra are muted to achiral solvent, cSFG can be used to characterize secondary structures at interfaces with zero water background. Using cSFG, we studied the aggregation of human islet amyloid polypeptide (hIAPP), which is associated with type II diabetes. We observed in situ and in real time the misfolding of hIAPP from disordered structures to alpha-helices and then beta-sheets on membrane surfaces. The results provide insight into the pathogenic mechanism for type II diabetes. The studies also demonstrate the capacity of cSFG in solving fundamental and engineering problems in biological and biomedical sciences.