Single-molecule orientation localization microscopy I: fundamental limits.

Area of Science:

• Biophysics
• Quantum Optics
• Microscopy

Background:

• Single-molecule experiments face significant photon shot noise, limiting precise 3D localization and orientation measurements.
• Existing techniques encode positional and orientational information into fluorescence images, but optimal precision remains a challenge.

Purpose of the Study:

• To develop a mathematical framework for determining the ultimate precision limits in measuring 3D position and orientation of dipole emitters.
• To evaluate the feasibility of designing an instrument for simultaneous optimal precision in all rotational and translational measurements.

Main Methods:

• Adaptation of classical and quantum estimation theory to derive fundamental precision limits.
• Development of a vectorial dipole imaging model for quantitative analysis.

Main Results:

• It is impossible to achieve maximum sensitivity for all possible rotational motions with a single instrument.
• The quantum-limited localization precision is 4%-8% lower than predicted by simpler scalar models.
• No single instrument can be optimized for all 2D and 3D localization and orientation measurement tasks.

Conclusions:

• The study establishes fundamental limits on the precision of single-fluorophore measurements under photon-starved conditions.
• Vectorial imaging models provide a more accurate assessment of achievable precision compared to scalar models.
• Optimizing instruments for specific measurement tasks is necessary, as universal optimization is not possible.