Probing microscopic conformational dynamics in folding reactions by measuring transition paths

Area of Science:

• Biophysics
• Chemical Physics
• Molecular Dynamics

Background:

• Transition paths are crucial for understanding molecular folding kinetics and mechanisms.
• These high-energy states are difficult to observe due to their transient nature.
• Single-molecule experiments offer a new window into these dynamics.

Purpose of the Study:

• To review single-molecule fluorescence and force spectroscopy measurements of transition path properties.
• To discuss the relationship between these measurements and folding theories.
• To highlight the potential for enhanced atomistic understanding through combined experimental and simulation approaches.

Main Methods:

• Single-molecule fluorescence spectroscopy
• Single-molecule force spectroscopy
• Analysis of transition path properties (time, velocity, shape, variability)
• Comparison with diffusion theories and molecular simulations

Main Results:

• Characterization of microscopic conformational dynamics during barrier crossings.
• Direct probing of transition path properties like duration, velocity, and shape.
• Variability in measurements reflects differences in individual barrier crossings.
• Successful relation of experimental data to diffusion over energy landscapes.

Conclusions:

• Transition path measurements provide detailed insights into molecular folding mechanisms.
• Combining experiments with simulations enhances atomistic understanding of folding.
• These advanced techniques promise significant improvements in understanding microscopic folding processes.