Barrier Crossing Dynamics from Single-Molecule Measurements.

Area of Science:

• Chemical Kinetics
• Physical Chemistry
• Biophysics

Background:

• Chemical reactions are often visualized as motion along one-dimensional reaction coordinates over free energy barriers.
• Existing rate theories (e.g., transition state theory, Kramers theory) make different assumptions about this motion.
• Direct observation of reaction coordinate motion requires high-time-resolution single-molecule experiments.

Purpose of the Study:

• To explore what can be learned about barrier crossing dynamics using single-molecule experiments, theory, and simulations.
• To investigate fundamental questions about reaction coordinate motion, such as its diffusive nature and the validity of single-degree-of-freedom models.
• To highlight how experimental data can be used to test theoretical models of chemical reactions.

Main Methods:

• Utilizing high-time-resolution single-molecule experiments to capture barrier crossing events.
• Employing molecular simulations to model and analyze reaction dynamics.
• Applying experimentally testable mathematical inequalities to analyze data from experiments and simulations.

Main Results:

• Emerging experimental data offers insights into the elusive reaction mechanisms of biomolecules.
• Analysis using mathematical inequalities has begun to answer fundamental questions about motion along reaction coordinates.
• The synergy between experiments, theory, and simulations is advancing the understanding of barrier crossing dynamics.

Conclusions:

• Single-molecule studies are providing unprecedented views into chemical reaction mechanisms.
• The developed methods allow for rigorous testing of assumptions in chemical rate theories.
• This research opens new avenues for understanding complex molecular processes and developing advanced theoretical models.