Nanoparticle surface-enhanced Raman scattering of bacteriorhodopsin stabilized by amphipol A8-35

Area of Science:

• Analytical Chemistry
• Biophysics
• Spectroscopy

Background:

• Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for molecular sensing, including at the single-molecule level.
• Membrane proteins (MPs) are crucial but challenging to study with SERS due to their amphiphilic nature.
• Amphipols (APols) can stabilize MPs, maintaining their solubility, stability, and functionality.

Purpose of the Study:

• To demonstrate the proof of concept for SERS analysis of APol-stabilized MPs.
• To explore the potential of SERS for single-molecule (SM) sensitivity with MPs.
• To use bacteriorhodopsin (BR) as a model system for APol-stabilized MP SERS studies.

Main Methods:

• Utilizing amphipol A8-35 to stabilize bacteriorhodopsin (BR) MPs.
• Preparing dried mixtures of silver nanoparticles (NPs) and BR/A8-35 complexes.
• Performing SERS measurements on the dried complexes.

Main Results:

• APol-stabilized BR remained functional after partial drying.
• SERS measurements yielded an average enhancement factor exceeding 10^2.
• SERS spectra were consistent with non-SERS spectra of the dried BR/APol complexes.

Conclusions:

• SERS is a feasible technique for analyzing APol-stabilized membrane proteins.
• This approach holds promise for single-molecule sensitivity studies of MPs.
• Amphipol stabilization is key to overcoming handling difficulties for MP SERS analysis.