Optical trapping of a single protein

Area of Science:

• Biophysics
• Nanotechnology
• Optical Physics

Background:

• Single-molecule detection is crucial for understanding biological processes.
• Optical trapping offers a non-invasive method for manipulating and probing molecules.
• Protein unfolding is a fundamental aspect of protein function and misfolding.

Purpose of the Study:

• To demonstrate optical trapping of a single bovine serum albumin (BSA) molecule.
• To investigate the effect of optical forces on protein structure.
• To establish a highly sensitive method for single-protein detection.

Main Methods:

• Utilizing a double-nanohole in an gold (Au) film for optical trapping.
• Employing optical tweezers to capture and manipulate a single BSA molecule (hydrodynamic radius 3.4 nm).
• Monitoring protein unfolding through changes in optical power and solution pH.

Main Results:

• Successful stable optical trapping of a single BSA molecule was achieved.
• The intense optical forces within the trap induced unfolding of the BSA molecule.
• Protein unfolding was confirmed by varying optical power and solution pH.
• A high signal-to-noise ratio of 33 was obtained for trapping event detection.

Conclusions:

• The double-nanohole optical trap is capable of stably trapping and unfolding single protein molecules.
• This technique provides an extremely sensitive method for detecting single protein molecules.
• The study highlights the potential of optical trapping for investigating protein dynamics and structure at the single-molecule level.