Water mediated electron attachment to nucleobases: Surface-bound vs bulk solvated electrons

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Biophysics

Background:

• Electron attachment to nucleobases is crucial for understanding DNA damage and repair mechanisms.
• Solvation effects significantly influence the behavior of electrons in biological systems.

Purpose of the Study:

• To elucidate the mechanism of electron attachment to solvated nucleobases.
• To investigate the role of water in stabilizing nucleobase anions.
• To determine the timescale of electron transfer from water to nucleobases.

Main Methods:

• Hybrid quantum/classical (QM/MM) simulations using accurate wave-function based methods.
• Utilized uracil as a model nucleobase.
• Analyzed electron localization, transfer dynamics, and solvation shell interactions.

Main Results:

• The initial electron attachment state localizes in bulk water, serving as a precursor to nucleobase binding.
• Electron transfer from water to uracil is facilitated by the mixing of electronic and nuclear degrees of freedom.
• Water molecules stabilize the uracil-bound anion via hydrogen bonding, accelerating electron attachment.
• Complete electron transfer occurs within picoseconds, consistent with experimental rates.
• Both surface-bound and bulk-solvated electrons lead to similar long-term anion behavior.

Conclusions:

• Water plays a critical role in mediating electron attachment to nucleobases.
• The QM/MM simulation approach accurately captures the dynamics of electron transfer and solvation.
• The findings provide insights into the initial steps of radiation-induced DNA damage.