One of the main challenges that deep space flight presents to astronauts is radiation. Space vehicles can be shielded but with currently technology this remains limited. One of the nearer-to-home challenges for a mission to Mars with a human crew is radiation. Hence, a significant hazard for astronauts traveling to Mars will be overcoming exposure to high energy radiation from the solar wind, solar storms, and galactic cosmic rays that originate outside of our solar system.
A new chemical and microbiological discovery, from Northwestern University and the Uniformed Services University (USU), finds how simple metabolites can combine to form a powerful antioxidant. It is through this powerful antioxidant the bacterium Deinococcus radiodurans can withstand radiation doses 28,000 times greater than what would kill a human. The bacterium is the second known most radiation-resistant micorganism (the most resistant are the archaeon Thermococcus gammatolerans).
The benefit of the research is aiding scientific understanding of how the antioxidant works and this insight could help to drive the development of ‘designer’ antioxidants to shield astronauts from cosmic radiation (a decapeptide called DP1).
The reason that the spherical D. radiodurans is so resistant to gamma radiation doses is the presence of a collection of simple metabolites, which combine with manganese to form the powerful antioxidant. This is all the more remarkable given that the bacterium does not form spores (the normal morphology linked to the most resistant bacterial species).
In a new study, the researchers characterized a synthetic designer antioxidant, called MDP, which was inspired by D. radiodurans’ resilience. They found, in relation to the extremophile, MDP’s components — manganese ions, phosphate and a small peptide — form a ternary complex that is a much more powerful protectant from radiation damage than manganese combined with either of the other individual components alone.
This discovery could eventually lead to new synthetic antioxidants specifically tailored to human needs. Applications include protecting astronauts from intense cosmic radiation during deep-space missions, preparing for radiation emergencies and producing radiation-inactivated vaccines.
The research builds on previous inquiries that sought to better understand D. radiodurans’ predicted ability to withstand radiation on Mars. This used an advanced spectroscopy technique to measure the accumulation of manganese antioxidants in the microbes’ cells. This revealed the size of the radiation dose that a microorganism can survive directly correlates with the amount of manganese antioxidants it contains (more manganese antioxidants mean more resistance to intense radiation).
D. radiodurans can survive 25,000 Grays in its normal vegetative state (after this, DNA cleavage occurs); however, when dried and frozen (as it might be on the hull of a spacecraft), the bacterium can survive 140,000 Grays of radiation, a dose 28,000 times greater than what would kill a human. A Gray is defined as the absorption of one joule of radiation energy per kilogram of matter. Against most microbes, 25 to 50,000 Grays are sufficient to achieve demonstrable sterilisation.
For the current study, the scientists identified a decapeptide called DP1. When combined with phosphate and manganese, DP1 forms the free-radical-scavenging agent MDP, which successfully protects cells and proteins against radiation damage.
By using advanced paramagnetic resonance spectroscopy, the scientists further revealed that the active ingredient of MDP is a ternary complex — a precise assembly of phosphate and peptide bound to manganese.
The research appears in the journal Proceedings of the National Academy of Sciences. The research is titled “The ternary complex of Mn2+, synthetic decapeptide DP1 (DEHGTAVMLK) and orthophosphate is a superb antioxidant.”
