Thermal neutron cross sections of amino acids from average contributions of functional groups

TL;DR

This study measures and interprets the thermal neutron cross sections of amino acids, enabling simplified modeling of complex biological systems for medical and experimental applications.

Contribution

It introduces a method to approximate amino acids' neutron cross sections using functional group contributions, aiding modeling of biological tissues.

Findings

Measured neutron cross sections for 20 amino acids.

Validated the average functional group contribution model.

Enhanced accuracy in neutron scattering simulations for biological samples.

Abstract

The experimental thermal neutron cross sections of the twenty proteinogenic amino acids have been measured over the incident-neutron energy range spanning from 1 meV to 10 keV and data have been interpreted using the multi-phonon expansion based on first-principles calculations. The scattering cross section, dominated by the incoherent inelastic contribution from the hydrogen atoms, can be rationalised in terms of the average contributions of different functional groups, thus neglecting their correlation. These results can be used for modelling the total neutron cross sections of complex organic systems like proteins, muscles, or human tissues from a limited number of starting input functions. This simplification is of crucial importance for fine-tuning of transport simulations used in medical applications, including boron neutron capture therapy as well as secondary neutrons-emission induced during proton therapy. Moreover, the parametrized neutron cross sections allow a better treatment of neutron scattering experiments, providing detailed sample self-attenuation corrections for a variety of biological and soft-matter systems.