title: Preliminary investigation of proton and helium ion radiation effects on fluorescent dyes for use in astrobiology applications.
abstract: The Specific Molecular Identification of Life Experiment (SMILE) instrument (Sims et al. Planet. Space Science 2005, 53, 781-791) proposes to use specific molecular receptors for the detection of organic biomarkers on future astrobiology missions (e.g., to Mars). Such receptors will be used in assays with fluorescently labeled assay reagents. A key uncertainty of this approach is whether the fluorescent labels used in the system will survive exposure to levels of solar and galactic particle radiation encountered during a flight to Mars. Therefore, two fluorescent dyes (fluorescein and Alexa Fluor 633) have been exposed to low-energy proton and alpha radiation with total fluences comparable or exceeding that expected during an unshielded cruise to Mars. The results of these initial experiments are presented, which show that both dyes retain their fluorescent properties after irradiation. No significant alteration in the absorption and emission wavelengths or the quantum yields of the dyes with either radiation exposure was found. These results suggest other structurally similar fluorophores will likely retain their fluorescent properties after exposure to similar levels of proton and alpha radiation. However, more extensive radiation fluorophore testing is needed before their suitability for astrobiology missions to Mars can be fully confirmed.
authors.affiliation: Space Research Centre, Department of Physics & Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK. dpt4@star.le.ac.uk
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Thompson
authors.forename: Paul K
authors.initials: PK
authors.lastname: Wilson
authors.forename: Mark R
authors.initials: MR
authors.lastname: Sims
authors.forename: David C
authors.initials: DC
authors.lastname: Cullen
authors.forename: John M C
authors.initials: JM
authors.lastname: Holt
authors.forename: David J
authors.initials: DJ
authors.lastname: Parker
authors.forename: Mike D
authors.initials: MD
authors.lastname: Smith
mesh_terms: D000042:Absorption; D003359:Cosmic Radiation; D018559:Exobiology / Q000379:methods*; D005118:Extraterrestrial Environment; D005456:Fluorescent Dyes / Q000737:chemistry*; D006371:Helium / Q000737:chemistry*; D007477:Ions; D018535:Mars; D011522:Protons; D011834:Radiation Monitoring; D011835:Radiation Protection; D014481:United States; D018557:United States National Aeronautics and Space Administration
chemical_list: D005456:Fluorescent Dyes; D007477:Ions; D011522:Protons; D006371:Helium