Radioresistance of adenine to cosmic rays
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Date
2017
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Abstract
The presence of nucleobases in carbonaceous meteorites on Earth is an indication of the existence of this class of molecules in outer space. However, space is permeated by ionizing radiation, which can have damaging effects on these molecules. Adenine is a purine nucleobase that amalgamates important biomolecules such as DNA, RNA, and ATP. Adenine has a unique importance in biochemistry and therefore life. The aim of this work was to study the effects of cosmic ray analogues on solid adenine and estimate its survival when exposed to corpuscular radiation. Adenine films were irradiated at GANIL (Caen, France) and GSI (Darmstadt, Germany) by 820 MeV Kr³³⁺, 190 MeV Ca¹⁰⁺, 92 MeV Xe²³⁺, and 12 MeV C⁴⁺ ion beams at low temperature. The evolution of adenine molecules under heavy ion irradiation was studied by IR absorption spectroscopy as a function of projectile fluence. It was found that the adenine destruction cross section (σd) follows an electronic stopping power (Se) power law under the form: CSeⁿ; C is a constant, and the exponential n is a dimensionless quantity. Using the equation above to fit our results, we determined σd = 4 × 10⁻¹⁷ Se1.17, with Se in kiloelectronvolts per micrometer (keV μm⁻¹). New IR absorption bands arise under irradiation of adenine and can be attributed to HCN, CN⁻, C2H4N4, CH3CN, and (CH3)3CNC. These findings may help to understand the stability and chemistry related to complex organic molecules in space. The half-life of solid adenine exposed to the simulated interstellar medium cosmic ray flux was estimated as (10 ± 8) × 10⁶ years.
Resumen
La presencia de nucleobases en meteoritos carbonosos en la Tierra es una indicación de la existencia de esta clase de moléculas en el espacio exterior. Sin embargo, el espacio está impregnado de radiación ionizante, que puede tener efectos dañinos sobre estas moléculas. La adenina es una nucleobase de purina que amalgama biomoléculas importantes como el ADN, el ARN y el ATP. La adenina tiene una importancia única en la bioquímica y, por tanto, en la vida. El objetivo de este trabajo fue estudiar los efectos de los análogos de los rayos cósmicos sobre la adenina sólida y estimar su supervivencia cuando se exponen a la radiación corpuscular.
Keywords
Heavy ions, Infrared spectroscopy, Astrochemistry, Cosmic rays, Nucleobases, Adenine