Controlled bimolecular collisions allow sub-diffraction limited microscopy of lipid vesicles

Area of Science:

• Optical Microscopy
• Nanotechnology
• Biophysics

Background:

• Conventional optical microscopy is limited by diffraction, hindering nanoscale imaging.
• Single-molecule experiments often suffer from photobleaching, complicating analysis.
• Controlling molecular interactions with biological assemblies is key for advanced imaging.

Purpose of the Study:

• To develop a novel optical microscopy technique for sub-diffraction limited imaging.
• To overcome photobleaching limitations inherent in traditional single-molecule studies.
• To achieve nanoscale spatial resolution by analyzing molecular collision kinetics.

Main Methods:

• Utilized controlled collisions between single Nile Red probe molecules and 50 nm hydrophobic vesicles.
• Analyzed fluorescence bursts from molecular collisions using on- and off-time distribution functions.
• Employed raster scanning to measure changes in mean burst frequency versus fluorescence intensity.

Main Results:

• Demonstrated that mean burst frequency changes sharply with vesicle scanning, exceeding fluorescence intensity changes.
• Showcased improved spatial resolution, enabling measurement of separations below the diffraction limit.
• Established that vesicle size and molecular concentration influence collision kinetics and burst frequency.

Conclusions:

• Trajectory Time Distribution Optical Microscopy (TTDOM) offers a viable method for sub-diffraction imaging.
• The technique effectively overcomes photobleaching issues in single-molecule optical experiments.
• TTDOM principles can be extended to create far-field optical systems with nanometer-scale resolution.