Single Molecule Studies Enabled by Model-Based Controller Design.

Area of Science:

• Biophysics
• Cell Biology
• Nanotechnology

Background:

• Optical tweezers are crucial for studying motor proteins and intracellular transport.
• Achieving precise force regulation under disturbances and thermal noise is challenging.
• Simultaneous force regulation and motion estimation objectives can conflict.

Purpose of the Study:

• To develop a robust framework for dual force regulation and motion estimation in optical tweezers.
• To address limitations in current optical tweezer methodologies for motor protein analysis.
• To provide quantifiable guarantees for both force control and movement tracking.

Main Methods:

• A mixed-objective H2/H-infinity optimization framework was designed.
• Model-based design was employed for integrated control.
• Minimization of H-infinity norm for force regulation and step estimation error.
• H2 norm of noise on step estimate was constrained.

Main Results:

• The framework successfully achieved simultaneous force regulation and real-time motion estimation.
• Experimental implementation with kinesin motor proteins demonstrated efficacy.
• Forces were regulated below 1 piconewton with less than 10% error.
• Real-time motion estimates of motor proteins were obtained.

Conclusions:

• The proposed H2/H-infinity framework offers a powerful solution for complex optical tweezer applications.
• This approach enhances the study of motor protein dynamics under controlled force conditions.
• It provides a reliable method for obtaining precise measurements in biophysical experiments.