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

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

3. Background Organic material is found in carbonaceous chondrite (CC) meteorites: <5% by mass (~14000 different molecules ( Schmitt-Kopplin et 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. ( Kvenvolden et 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. Fluorescence - Overview Emitted light λ than the light absorbed Usually, emission ceases almost instantaneously as irradiation is terminated (ns to μs timescale)

6. The sensor – Introducing the lanthanides 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

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

8. The sensor – EuDOTA and TbDOTA

9. Preliminary research 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 λ may be similar to Eu and Tb Organic excitation below that of Eu and Tb so not a concern Mineral fluorescence, activated and intrinsic, can be background corrected

10. Preliminary research – DOTA experimentation 1)DOTA was synthesised 2)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

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 mol dm -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 – Eu 3+ (aq) /EuDOTA/EuDO3A comparison

18. EuDO3A fluorimetric analysis – EuDO3A and all analytes

19. (L)-serine (L)-tyrosine (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)-serine (L)-ornithine (L)-tyrosine (L)-threonine (L)-aspartic acid Benzoic acid

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