Synthesis of nucleotides in space

1. Synthesis of nucleotides in space Natalia Gontareva Laboratory of Exobiology, Institute of Cytology St Petersburg, Russia ngontar@mail.cytspb.rssi.ru Nordic winter school on Astrobiology

2. Background • Two groups of life origin theories: • Terrestrial origin. • Extraterrestrial origin. Planets are not isolated in terms of biology and exchange of organic material could occur between them. • Possibility for cosmic delivery of basic molecules: • Amount of micrometeorites (from 50 to 500 m in size) – 50-100 tons daily. • Meteorite flux - 0.03 tons per day. • Heavy bombardment in early Earth - 1000 times more than present amount. • High percentage of organic components in carbonaceous chondrites • Availability of different space energy sources • Presence of organics in space (molecular hydrogen, water, CO, HCN, etc.) Nordic winter school on Astrobiology

3. Organic molecules in space Nordic winter school on Astrobiology

4. Potential sites for organic molecules formation as the result of prebiotic chemical processes. Localisation Temperature, К Particles concentration, cm-3 Sources of energy 1. Interstellar clouds Cold 10 103 Cosmic rays Hot core 50 105 Cosmic rays 2. Protosolar nebula External part 60 109 Solar wind Internal part 600 1012 Solar wind 3. Comets Surface 20 or 100 1019 Stellar UV and cosmic rays Core 20 or 500 1019 26Al 4. Comets after capture by planets Surface 2-200 1019 Solar vacuum ultraviolet 5. Primordial Earth Hydrosphere 330 1019 Solar ultraviolet Lower atmosphere 330 1016 Lightning Nordic winter school on Astrobiology

5. Hydrogen Cyanide (HCN) As the Source for Prebiotic Synthesis • hydrogen cyanide polymers may be present on different bodies of the outer solar system (comets, Titan) • Hydrogen cyanide polymers deposided by comets may have established protein-nucleic acid life on Earth • Chemical precursor of both purines and pyrimidines, source for prebiotic synthesis Nordic winter school on Astrobiology

6. Sugars in space • Ethylene glycol was discovered recently in a massive interstellar cloud of dust and gas near the center of the Milky Way Galaxy. Scientists used the National Science Foundation's (NSF) 12 Meter Radio Telescope to detect this organic molecule. • Ethylene glycol (a 10-atom molecule made up of carbon, hydrogen, and oxygen) is one of the five largest molecules ever discovered in space. • It also is a chemically reduced form of 8-atom glycolaldehyde, the simplest member of the sugar family. • It can be produced from glycolaldehyde by the addition of two hydrogen atoms. Both molecules have now been detected in space by this team. Nordic winter school on Astrobiology

7. Molecular structure of nucleotides Nordic winter school on Astrobiology

8. Nucleotides base pairing Nordic winter school on Astrobiology

9. Scheme of nucleotide synthesis • 5'-mononucleotides are the prevailing derivatives synthesized of certain nucleosides • 3’, 2’ and cyclic monophosphates present in similar quantities • Di-and triphosphates also present in the reaction mixture Nordic winter school on Astrobiology

10. Possible scenario of life transfer in the Solar system From Horneck Nordic winter school on Astrobiology

11. Energy sources in space: • Solar electromagnetic radiation from 2*10-12 to 102 m • Solar corpuscular radiation (solar wind – low and high energy solar particle events) – predominantly protons with 10% helium ions and 1% heavy ions and electrons • Cosmic galaxy radiation originates from outside our solar system - 87% protons (hydrogen nuclei), 12% alpha particles (helium nuclei), 1.3% heavy ions (fully ionized ions of all elements from protones to uranium with Z 92), 1% electrons. • Extreme temperatures, from 4K and more • Earth orbit energy: solar radiation (1360 W*m-2), Earth albedo (480 W m-2); terrestrial radiation (230 W*m-2). Nordic winter school on Astrobiology

12. Solar electromagnetic radiation • Driving force for many biological reactions because of its abundanceh. Approximate intensity of UV254 radiation in the lower Martian atmosphere level equals to 105 J m-2 h-1. • The UV flux: near (300-400 nm) and far (200-300 nm) • Short-wave UVC (less than 280 nm) must be considered in any extraterrestrial situation when looking for the possibility of sustaining life. • Radiation at the wavelength of 254 nm is capable of interacting directly with molecular structures. UV radiation causes temporary or permanent alterations that result from photochemical reactions of UV 254 with different biological target molecules, the so-called chromophores. • The response of different biological structures to UV exposure is unique. It can be altered by surface composition of space bodies, so the mineral component of environment should not be underestimated. Nordic winter school on Astrobiology

13. The contribution of short UV to the synthesis of nucleotides in different radiation conditions Flight data (MIR) UV 145 UV 254 Nordic winter school on Astrobiology

14. Absorption spectra of DNA, RNA and nucleobases • UV 254: The absorbing parts of DNA are the bases.There is absorption maximum at 260 nm and a rapid decline towards longer wavelengths. • UV 145: Absorption increases due to phosphates, riboses and ribophosphates G G A A T U C C Fig. 2 – from top to bottom: 1 - RNA spectrum, nucleobases: 2 – Gua, 3 – Ade, 4 – Ura, 5 - Cyt Fig. 1 – from top to bottom: 1 - DNA spectrum, nucleobases: 2 – Gua, 3 – Ade, 4 – Thy, 5 – Cyt. a and b curves correspond to different concentrations Nordic winter school on Astrobiology

15. Possible sites of photocatalytic processes in interstellar medium (ISM) • ISM – the space between stars consisting of gas and dust. • Most probable source of organic molecules – non-equilibrium processes driven by photons, cosmic rays, shock waves and solid bodies’ collisions • The dense cold phase of ISM host icy dust grains – important chemical catalyst during its life cycle • Such particles consist of mineral core composed by silicate or olivine admixed with metal sulfides and oxides, with the water-icy envelope containing organic molecules • Organic molecules in the ISM evolve and become later incorporated in solar system material (comets and meteorites) Nordic winter school on Astrobiology

16. UV-irradiation of the molecules adsorbed by mineral matrix of the interstellar dust • As dust grains with ice mantles are transported to warm, dense, and active protostellar regions, the ultraviolet irradiation may become important and alter the grain composition. • Spectral selectivity of photocatalyst: short-wave photons are totally adsorbed by a thin outer layer, whereas the photons of longer wavelength can penetrate into much deeper layers • Photoadsorbtion and photocatalytic memory: the irradiation of some solids creates active photocatalytic centers. These are lattice defects with a trapped photocarrier, electron or a hole. Pre-irradiated particle stays in metha-stable state for a long time • Excitation energy “concerved” within the solid matrix is released to activate chemical reaction at its surface. • This phenomenon can compensate the effects of low reagents concentration and temperature Nordic winter school on Astrobiology

17. Basalt mineral composition Nordic winter school on Astrobiology

18. Limonite limonite Class: Oxide/Hydroxides Color(s): yellow, brown, glassy, Hardness: 4-5.5 SpecGrav: 2.7-4.3 Fracture: conchoidal, uneven Crystal: Amorphous, fibrous, botryoidal - limonite is not really a mineral but rather a mixture of hydrated goethite. Envronment: a mixture of secondary iron minerals, alteration product of iron ores, especially sulfides Association: pyrite, hematite, prolusite, psilomelane, calcite, quartz Nordic winter school on Astrobiology

19. Interaction of montmorillonite ((Na,K,Ca)(Аl,Fe,Мg)[(Si,Al)4O10](OH)2*nH2O) catalytic sites and organic molecules а – The binding of monomers. The catalysis is ascribed to the orientation of monomers and the acidity of the surface (electrostatic interaction of the protonated base and negatively charged surface) в – Activation of functional groups of monomers. Adsorption on the clay favors reaction between monomers. с – The release of oligomers from the mineral surface. Final reaction involves two neighbor activated molecules. From Ferris Nordic winter school on Astrobiology

20. Molecular cloud Azo-dyes based supermolecules of fullerene (ErSc2N@[CH2CH2NH]C80, figure on left) and a biliverdin (figure on right) derivatives. Such a molecular cloud may absorb magnetic and light energy from planets and stars, move in the Space by using light wind collecting all necessary molecules for the growing and multiplication. From Tamulis Nordic winter school on Astrobiology

21. The aims of MIR space experiments were: • To study the contribution of lunar soil to the processes of prebiotic solid phase synthesis of peptides and nucleotides • To evaluate the role of space energy sources in this synthesis • To test the amount of initial substances’ decay after long-duration space flight • To model the surface of small cosmic body • The aims of laboratory experiments were: • To perform control experiments proving flight data • To study the influence of extraterrestrial minerals over solid phase synthesis of peptides and nucleotides • To evaluate the effect of different energy sources present in cosmic environment Nordic winter school on Astrobiology

22. Unique property of the experiments at the orbit: • Modeling of the early Earth and space bodies radiation environment • Approximation of the continuos space flight: • Energy flux in diffused interstellar medium (photons more than 6 eV) - 108 photon*cm-2*s-1. • At the orbit – intensity of solar radiation for 6 eV photons is 9*1015 photon*cm-2*s-1. Hence the amount of radiation gained at the orbit during two weeks flight is equal to the 2*106 years long interstellar flight. Nordic winter school on Astrobiology

23. Components in carbonaceous chondrites (in %)*. 1) Allende meteorite (CV3) 2) Murchison meteorite powder( CM2) 3) Lunar soil: significant micrometeoriticcomponent (similar to C1 chondrites). *(Rosanov, 1996) Nordic winter school on Astrobiology