Molecular Structures and Molecular Interactions of Peptides and Proteins at Buried Interfaces Studied Using Sum Frequency Generation Vibrational Spectroscopy

Interfacial behavior of peptides and proteins plays important role in many biological processes and applications, ranging from membrane protein function, antimicrobial activity, biosensor sensitivity, antibody drug stability, and antifouling coating performance, to implant biocompatibility. Such interfacial behavior is mediated by peptide/protein interfacial molecular structures such as secondary structures, orientations, conformations, oligomeric forms, and adsorption sites. Many traditional chemical and physical methods are unable to detect molecular‐level structural information of proteins and peptides at buried interfaces in situ and in real time. Sum frequency generation (SFG) vibrational spectroscopy is a specialized technique that can be used to elucidate molecular structures and interactions of peptides and proteins at buried interfaces. In this review, we discuss the recent advancements in using SFG as the primary method for probing peptides and proteins at buried interfaces. We first cover the qualitative structural information that can be obtained from SFG alone. Then we discuss how the additions of crystal structures, computational techniques—such as our Hamiltonian spectral calculation and matching program and Molecular Dynamics simulations—and isotope labeling to our method can provide a more quantitative and complete understanding of protein/peptide behavior and functionality at buried interfaces.