Aim of the Research

1. NOVEL FLUORESCENT SENSORS FOR THE DETECTION OF ORGANIC MOLECULES IN EXTRA-TERRESTRIAL SAMPLESRoy C. Adkin, James I. Bruce and Victoria K. Pearson Twitter: @RCAdkin

2. Development of a fluorescent lanthanide complex which will interact with meteoritic organic species in situ and/or in the aqueous phase Aim of the Research

3. Background • Organic material is found in carbonaceous chondrite (CC) meteorites: <5% by mass (~14000 different molecules (Schmitt-Kopplinet al., 2010)) • Although (most) confirmed as extra-terrestrial in origin due to: • Isotope ratios (H/D, C, N, O) • Structural isomerisation and diversity e.g. racemic ratio, branching • Compounds present in higher concentrations but rare on Earth, e.g., isovaline, pseudoleucine etc. (Kvenvoldenet al., 1970) • No defined environment of formation for what is seen in meteorites although several possible cosmological provinces suggested • BUT, minerals are formed under distinct chemical and physical conditions so can be used as environmental indicators (Velde, 2000) • Understanding mineral/organic associations more could help clarify organic compound source regions and formation processes

4. The problem • We know a relationship exists; • Amount of matrix vs bulk organic material indicated by C and N content (e.g. Anders et al., 1973) • Removal of minerals by dissolution releases more organic material (e.g. Sephton and Gilmour, 2001) • Basic labelling reveals organic material predominately associated with matrix (e.g. Pearson et al., 2007) • Organic molecular inventory and concept of mineral/organic material associations elucidated by destructive analysis of carbonaceous chondrites Development of a new, non-destructive, in situ analytical tool is required…

5. Emitted light < energy and > λ than the light absorbed Fluorescence - Overview EMISSION IRRADIATION Usually, emission ceases almost instantaneously as irradiation is terminated (ns to μs timescale)

6. Lanthanides (Ln) are elements, e.g. europium (Eu) and terbium (Tb) - amongst the most luminescent elements in the Periodic Table • Extensively used in biomedical imaging techniques • Lanthanide metal ion coupled to an organic ligand • ‘Fingerprint’ emission spectrum consisting of line-like peaks or bands – indicative of the element • Have long fluorescent lifetimes – the time between termination of irradiation and cessation of emission (ms) • Ln must be stable, chemically inert yet subject to physical interactions The sensor – Introducing the lanthanides

7. Commercially available The sensor – ligand: DOTA 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraethanoic acid

8. The sensor – EuDOTA and TbDOTA

9. Sources of intrinsic CC fluorescence • Some minerals exhibit fluorescent properties • Presence of Eu or Tb can activate, enhance or intensify that fluorescence • Identify organic and inorganic CC components whose excitation and emission λmay be similar to Eu and Tb Preliminary research • Organic excitation below that of Eu and Tb so not a concern • Mineral fluorescence, activated and intrinsic, can be background corrected

10. DOTA was synthesised • Suitable analytes were chosen representative of all classes of organic molecules identified in CCs taking into consideration: • The number and type of reactive sites and functional groups • Likelihood of interaction with the sensor – structure/size • Whether they are terrestrially rare or potentially prebiotic • Solubility in water Preliminary research – DOTA experimentation

11. Results of DOTA experiments and discussion • 1 mM LnDOTA solution mixed with a range of meteoritic organic molecules at concentrations expected in CCs • Spectra showed no peak shifts but a slight, yet trendless, variation in intensity • Lack of spectral deviation • No interaction with metal centre? • Lanthanide/analyte interaction but fluorescence not altered by presence of analyte? • Limit of detection? • Concentrations consistent with chondritic organic matter (µM, 10-6 mol dm-3, to nM, 10-9 moldm-3) may be too low for detection by this sensor

12. Fluorimetric analysis – Equimolar (1 mM) EuDOTA/analyte analysis

13. Fluorimetric analysis – Equimolar (1 mM) TbDOTA/analyte analysis

14. DOTA Fluorimetric analysis – Conclusion • Would expect analytes to increase fluorescent intensity due to displacement of water molecules • No discernible trend regarding analyte structure; • It was expected that conjugated and aromatic analytes could increase fluorescent intensity by absorption of excitation energy • Hypothesis: DOTA ligand does not afford interactions • Steric hindrance • Ln atom is too well enveloped • Cannot be sure of limit of detection • Solution? – Use DO3A ligand…one less pendant arm

15. The new ligand – DO3A

16. Fluorimetric analysis – EuDOTA/TbDO3A comparison

17. Fluorimetric analysis – Eu3+(aq)/EuDOTA/EuDO3A comparison

18. EuDO3A fluorimetric analysis – EuDO3A and all analytes

19. EuDO3A fluorimetric analysis – EuDO3A and all analytes (L)-tyrosine (L)-serine (L)-threonine

20. EuDO3A/EuDOTA fluorimetric analysis - conclusions • EuDOTA and EuDO3A have shown intensity increase with certain structures or chemical classes only • Identification of structures or functional groups is feasible • Individual molecular specificity may not be achievable

21. Future work • Produce standards for mixtures of: • Similar compound classes (e.g. all amino acids or all carboxylic acids etc.) • Similar or analogous structures (e.g. hypoxanthine and cytosine or adenine and 2,4-diaminopyrimidine etc.) • Complex mixtures of classes and structures • Introduce LnDOTA and LnDO3A complexes to these mixtures • Measure the effects on Ln fluorescent properties

22. Future work (continued) • Development of other ligand molecules • change nature of the pendant arms • facile ligand modifications • broaden the scope of interactions with analytes • selectivity and sensitivity • Development of methodology for future solid sample analysis

23. Thank you for listening. Any questions? Twitter: @RCAdkin Email: Roy.Adkin@open.ac.uk

24. Fluorimetric analysis – Analyte structures (L)-ornithine (L)-tyrosine (L)-serine (L)-threonine (L)-aspartic acid Benzoic acid

25. Fluorimetric analysis – Analyte structures Maleic Acid Fumaric acid Cytosine Hypoxanthine Adenine Itaconic acid N-guanylurea 2,4-diaminopyrimidine