Ionization and fragmentation of uracil upon microhydration

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Biophysical Chemistry

Background:

• Uracil is a fundamental nucleobase with significant biological roles.
• Understanding uracil's reactivity is crucial for molecular biology and drug design.
• The influence of microhydration on nucleobase behavior is an area of active research.

Purpose of the Study:

• To investigate the effects of microhydration (0-2 water molecules) on uracil's ionization and fragmentation.
• To elucidate how water molecules alter the reactivity and fragmentation mechanisms of uracil.
• To identify novel reaction pathways and stabilizing effects induced by microhydration.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Calculations focused on ionization potentials (adiabatic and vertical) and dissociation channels.
• Analysis included identifying transition states and minima for uracil-water complexes.

Main Results:

• Microhydration lowers adiabatic ionization potential by 0.41 eV and vertical ionization potential by 0.22 eV.
• Activation energies for dissociation channels increase by up to 0.5 eV due to microhydration.
• Formation of specific fragments, like those from C5-C6 cleavage, is restricted.

Conclusions:

• Microhydration significantly alters uracil's electronic properties and chemical reactivity.
• New transition states and minima were identified, indicating modified fragmentation mechanisms.
• The study confirms a stabilizing effect of microhydration on uracil, consistent with experimental findings.