Studies of electron migration in DNA in aqueous solution using intercalating dyes.

Area of Science:

• Chemical kinetics
• Radiation chemistry
• Molecular biology

Background:

• The hydrated electron (e-aq) and hydroxyl radical (OH) are reactive species that can interact with DNA.
• Intercalating dyes like proflavine and ethidium can bind to DNA, potentially altering its reactivity.

Purpose of the Study:

• To study the reactions of e-aq and OH with double-stranded DNA.
• To investigate the influence of intercalating dyes (proflavine, ethidium) on these reactions.
• To determine the extent of electron migration within DNA.

Main Methods:

• Studied reactions in aqueous solution at room temperature.
• Utilized intercalating dyes proflavine and ethidium.
• Measured rate constants for reactions between DNA, dyes, e-aq, and OH.

Main Results:

• Dyes reacted with e-aq at high rate constants (2.5-3.0 x 10^10 M^-1 s^-1).
• DNA-bound dyes showed reduced reaction yields and rate constants with e-aq (~2 x 10^9 M^-1 s^-1).
• No evidence of free electron migration in DNA was found; an upper limit of five base pairs was estimated.

Conclusions:

• Reactions of e-aq and OH with DNA-bound dyes are consistent with diffusion-controlled processes.
• The DNA structure restricts reactions, with a rate constant of approximately 2 x 10^9 M^-1 s^-1 per base unit.
• Limited electron migration within DNA was observed.