Determination of protein conformation and orientation at buried solid/liquid interfaces

Area of Science:

• Biophysics
• Surface Science
• Spectroscopy

Background:

• Protein structures at solid/liquid interfaces are crucial for various applications.
• Probing these structures *in situ* at buried interfaces at the molecular level remains challenging.

Purpose of the Study:

• To develop a systematic methodology for determining protein molecular structures (orientation and conformation) at buried solid/liquid interfaces *in situ*.
• To investigate the molecular structures of wild-type protein GB1 and its mutant at a polymer/solution interface.

Main Methods:

• Combined approach using sum frequency generation (SFG) vibrational spectroscopy, isotope labeling, spectra calculation, and computer simulation.
• Nonlinear optical spectroscopic technique for *in situ* analysis.

Main Results:

• Successfully determined molecular structures of protein GB1 and its mutant at the polymer/solution interface.
• Detected markedly different orientations and similar (but not identical) conformations between wild-type and mutant GB1.
• Varied molecular interfacial interactions influenced protein structure.

Conclusions:

• A systematic strategy was developed to elucidate protein structures at buried interfaces *in situ*.
• The methodology is general and applicable to a wide range of proteins and interfaces.