Biological Macromolecules at Interfaces Probed by Chiral Vibrational Sum Frequency Generation Spectroscopy

Chiral sum frequency generation (SFG) is surface-specific and chiral-selective under the electric-dipole approximation and in the absence of electronic resonance for the molecular systems with a chiral interface in contact with isotropic bulk media. The surface-specificity and chiral-selectivity makes vibrational SFG spectroscopy a uniquely useful tool for probing biomacromolecules at interfaces in situ and in real time. The method is particularly powerful for probing biomacromolecules at aqueous interfaces because achiral water structures do not contribute to the background. Chiral vibrational SFG spectroscopy has already been applied to the study of DNA molecules and various proteins, yielding information about the structures, orientation, and kinetics of conformational changes. It can be extended to other biomacromolecules, such as RNA, glycans, synthetic biomimetics, and chiral polymers. The unique surface-specificity and chiral-selectivity of the SFG method are expected to create research opportunities to address important problems in fundamental and engineering sciences. high-resolution SFG enabled by strong and narrow bandwidth picosecond visible input in broad bandwidth spectrometers may also introduce the opportunity to study the dynamics and structures of biomacromolecules in fine vibrational details.