Overview of antiproton affinities for functional groups relevant in particle‐beam cancer therapy

Abstract

Background:The recent advances in the production and storing of antiprotons inspire further research regarding using an antiproton particle beam in cancer therapy.In this work, an overview study of the chemical properties that govern the reactions between biomolecules and slowly moving antiprotons have been investigated. Aim:The motivation for the article is to grant an improved understanding of the processes involved in antiproton particle-beam cancer therapy as the antiproton comes to rest, in terms of the impact of molecular chemical properties on the antiproton annihilation site of the biomolecule. Methods and results:The potential energy surfaces for an antiproton in the vicinity of common functional groups in the human body have been calculated at the CASSCF/CASPT2 level. The energies at different antiproton distances are calculated and compared between different functional groups.A comparison of the impact on the antiproton affinity from atomic number, bond order, number of lone pairs, bond polarization due to electronegativity, and charge is presented. Conclusion:The lone pair effect and bond polarization have a relatively large impact. This implies that even on the isolated molecular level, the chemical environment governing the trajectory of an antiproton is a complex problem. The study is applicable primarily in the ultra-low energy collision regime but can also function as a starting point for quantum dynamical treatments.