A primary hydrogen-deuterium isotope effect observed at the single-molecule level

Area of Science:

• Biophysical chemistry
• Single-molecule chemistry
• Nanotechnology

Background:

• Covalent reactions can be monitored by observing ionic current changes through a protein pore.
• This nanoreactor approach allows real-time observation of molecular events.

Purpose of the Study:

• To examine the reductive 1,4-Michael addition reaction between a quinone and a thiol using a single-molecule nanoreactor.
• To detect and measure primary hydrogen-deuterium isotope effects at the single-molecule level.

Main Methods:

• Utilized a protein pore as a nanoreactor to confine reactants.
• Monitored time-dependence of ionic current flow to observe bond formation and breaking.
• Applied a hydrogen-deuterium isotope labeling strategy to study reaction mechanisms.

Main Results:

• Successfully monitored the covalent chemistry of quinone-thiol reaction in real-time.
• Detected a primary hydrogen-deuterium isotope effect during the prototropic rearrangement of an intermediate adduct.
• Demonstrated the ability to measure isotope effects for individual reaction intermediates, irrespective of whether the step is rate-limiting.

Conclusions:

• Single-molecule nanoreactors provide a powerful platform for studying reaction kinetics and mechanisms.
• This method allows for the detection of isotope effects that may be obscured in ensemble measurements.
• The approach is versatile for investigating various covalent reactions at the molecular level.