Effects of neutron radiation generated in deep space-like environments on food resources.

The impact of deep space cosmic rays on food resources is as important as the risks of cosmic rays to the human body. This study demonstrates the potential for neutrons as secondary radiation in deep space spacecraft to cause meat activation and oxidative modification of proteins and lipids. We conducted a series of experiments such as the neutron irradiation experiment, the radioactivation analysis and the biochemical analysis. Neutrons with energies from 1 to 5 MeV with doses from 0.01 Gy to 4 Gy were irradiated by the RIKEN accelerated-driven neutron source (RANS). Radioactive nuclei, Na, K, and Cl, were detected in the neutron-irradiated meat. The modification products of the proteins by oxidative nitration, 6-nitrotryptophan (6NOTrp), and by a lipid peroxidation, 4-hydroxy-2-nonenal (4-HNE), were detected in several proteins with neutron dose dependent. The proteome analysis showed that many oxidative modifications were detected in actin and myosin which are major proteins of myofibrils. This study is of crucial importance not only as risk factors for human space exploration, but also as fundamental effects of radiation on the components of the human body.