Theoretical Sum Frequency Generation Spectroscopy of Peptides

Joshua K. Carr, Lu Wang, Santanu Roy, James L. Skinner

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

Vibrational sum frequency generation (SFG) has become a very promising technique for the study of proteins at interfaces, and it has been applied to important systems such as anti-microbial peptides, ion channel proteins, and human islet amyloid polypeptide. Moreover, so-called "chiral" SFG techniques, which rely on polarization combinations that generate strong signals primarily for chiral molecules, have proven to be particularly discriminatory of protein secondary structure. In this work, we present a theoretical strategy for calculating protein amide I SFG spectra by combining line-shape theory with molecular dynamics simulations. We then apply this method to three model peptides, demonstrating the existence of a significant chiral SFG signal for peptides with chiral centers, and providing a framework for interpreting the results on the basis of the dependence of the SFG signal on the peptide orientation. We also examine the importance of dynamical and coupling effects. Finally, we suggest a simple method for determining a chromophore's orientation relative to the surface using ratios of experimental heterodyne-detected signals with different polarizations, and test this method using theoretical spectra. (Figure Presented).

Original languageEnglish
Pages (from-to)8969-8983
Number of pages15
JournalJournal of Physical Chemistry B
Volume119
Issue number29
DOIs
StatePublished - Jul 23 2015
Externally publishedYes

Funding

FundersFunder number
National Institutes of Health1R01DK088184
National Institute of Diabetes and Digestive and Kidney DiseasesR01DK088184

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