Orientation determination of interfacial bent α-helical structures using Sum Frequency Generation vibrational spectroscopy

•A formal SFG data analysis approach on bent α-helical structures was proposed.•The twist angle of α-helical structures was shown to be important in the analysis.•The interaction between melittin and DPPG was examined by this proposed approach.•The transient pore model was validated by the data analysis proposed in this study.

Sum Frequency Generation (SFG) has been shown to be a powerful and versatile technique in studies of proteins/peptides at surfaces and interfaces. Recently SFG was successfully applied in studies of interfacial macro-molecules with increasing size and complexity. In this report we continued to employ bond additivity model and group theory to demonstrate the importance of both the inter-helical tilt angle and the lengths of the helical segments assembling the structures being studies. Specifically, a newly improved SFG data analysis of multiple α-helical structures on melittin was used to interpret the SFG experimental observation and also verified the findings with the recent insights brought by other spectroscopic techniques.

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