Resolving cargo-motor-track interactions with bifocal parallax single-particle tracking

Area of Science:

• Cellular and Molecular Biophysics
• Biomolecular Interactions and Dynamics
• Nanobiotechnology

Background:

• Understanding molecular nanomachines requires resolving biomolecular interactions within living cells.
• Conventional tracking methods struggle to capture rotational dynamics crucial for motor function and binding status.
• Rotational information is key to interpreting the work performed by molecular motors.

Purpose of the Study:

• To develop a novel single-particle tracking method for real-time, full 3D motion and rotational analysis.
• To investigate the dynamics of intracellular transport, including cargo-motor-track interactions.
• To uncover previously unobserved interactions at microtubule intersections.

Main Methods:

• Development of a bifocal parallax single-particle tracking method utilizing half-plane point spread functions.
• Real-time acquisition of full-range azimuth angle (0-360°), polar angle, and 3D displacement.
• Application of the method to analyze cargo motion within a 3D cell cytoskeleton under living conditions.

Main Results:

• Quantitative rotational and translational motion of cargo in the 3D cell cytoskeleton was successfully obtained.
• Observed well-known intracellular transport mechanisms, including active transport and free diffusion.
• Discovered novel interactions: 'tight attachment' and 'tethered rotation' at microtubule intersections.

Conclusions:

• The bifocal parallax method enables comprehensive real-time analysis of biomolecular dynamics in living cells.
• New insights into cargo-motor-track interactions provide a deeper understanding of intracellular transport mechanisms.
• The findings offer a more complete interpretation of molecular motor function and binding dynamics.