Biomedical Engineering Reference
In-Depth Information
Chapter 6
Resonances in Electron Collisions with Small
Biomolecules Using the R-Matrix Method
Lilianna Bryjko, Amar Dora, Tanja van Mourik, and Jonathan Tennyson
Abstract
It is now widely accepted that collisions with low-energy electrons are
the major cause of radiation damage in living cells and that it is the capture of
these electrons into long-lived quasi-bound states, resonances, that is responsible
for this damage. We have undertaken a set of systematic calculations using the
UK Molecular R-matrix codes to study electron collisions with DNA and RNA
bases. Here we summarise the results of our calculations for electron collisions with
adenine, guanine, uracil, cytosine and thymine. These studies aim to characterize not
only low-lying shape resonances, which have been relatively well-studied, but also
to detect longer-lived Feshbach resonances which are associated with simultaneous
electronic excitation of the target molecule. The results of these calculations are
dependent on the model chosen: only the more sophisticated, and computationally
expensive, models give Feshbach resonances.
6.1
Introduction
The processes that follow the creation of thousands of low-energy electrons are now
recognised as being extremely important [
8
]. These electrons are stripped off from
molecules in the cell either directly by radiation or else by its first products, highly
energetic primary electrons that can cause electron-impact ionisation. As a result,
in the past few years, a growing literature has emerged concerning the damage to
