Probing the charge-transfer dynamics in DNA at the single-molecule level

Area of Science:

• Photochemistry
• Biophysics
• Molecular Biology

Background:

• Photoinduced charge-transfer (CT) in fluorescent dyes quenches fluorescence, creating a charge-separated state.
• Charge recombination (CR) reverses this process, making reactions reversible.
• CR dynamics are often overlooked but crucial for understanding fluorescence blinking in single-molecule measurements.

Purpose of the Study:

• To investigate charge recombination dynamics of fluorescent dyes using DNA as a platform.
• To demonstrate the potential of fluorescent dyes for monitoring charge-separation and charge-recombination events.
• To develop a method for DNA sequence readout based on CR dynamics.

Main Methods:

• Utilized DNA as a platform for spectroscopic investigations.
• Employed transient absorption spectroscopy to observe CR dynamics.
• Applied fluorescence correlation spectroscopy (FCS) for single-molecule level CR measurements.

Main Results:

• Demonstrated that fluorescent dyes (TAMRA, ATTO 655, Alexa 532) can monitor CT and CR events.
• Successfully measured CR dynamics in DNA at the single-molecule level using ATTO 655.
• Showcased DNA sequence readout by measuring charge return times.

Conclusions:

• Charge recombination dynamics of fluorescent dyes can be effectively studied on a DNA platform.
• Single-molecule fluorescence measurements can be enhanced by analyzing CR dynamics.
• This approach offers a novel method for DNA sequence analysis via charge dynamics.