Molecular basic data calculation for radiation transport in chromatin.

Area of Science:

• Chemical Physics
• Molecular Biophysics
• Computational Chemistry

Background:

• Understanding molecular interactions with electrons is crucial for fields like radiation biology and materials science.
• Electron impact ionization cross sections provide fundamental data on molecular targets.
• Data for biological molecules like DNA bases, backbone, and amino acids are essential but often scarce.

Purpose of the Study:

• To compute differential and integral electron impact ionization cross sections for DNA bases, the sugar-phosphate backbone, and 19 amino acids.
• To provide theoretical data for molecules relevant to biological systems and histone proteins.
• To compare calculated results with existing experimental and theoretical data where available.

Main Methods:

• Utilized the binary-encounter-Bethe (BEB) theoretical model for calculating ionization cross sections.
• Employed the General Atomic Molecular Electronic Structure System (GAMESS) for computing molecular orbital binding energies and populations.
• Focused on core-level ionization for the specified biological molecules.

Main Results:

• Calculated electron impact ionization cross sections for DNA bases, sugar-phosphate backbone, and 19 constituent amino acids of histone proteins.
• Obtained binding energies and molecular orbital populations using quantum chemical calculations.
• Demonstrated good agreement between calculated and published results for DNA bases and backbone.

Conclusions:

• The binary-encounter-Bethe model provides reliable cross-section data for biological molecules.
• This work presents novel theoretical data for amino acid ionization, filling a significant knowledge gap.
• The findings contribute valuable information for understanding radiation interactions with biological matter.