Synthesis of nucleotides in space

1
Synthesis of nucleotides in space

• Natalia Gontareva
• Laboratory of Exobiology, Institute of Cytology
• St Petersburg, Russia
• ngontar_at_mail.cytspb.rssi.ru

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.)

3
Organic molecules in space
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Potential sites for organic molecules formation
as the result of prebiotic chemical processes.  
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

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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.

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Molecular structure of nucleotides
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Nucleotides base pairing
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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

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Possible scenario of life transfer in the Solar
system
From Horneck
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Energy sources in space

• Solar electromagnetic radiation from 210-12 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 Wm-2),
  Earth albedo (480 W m-2) terrestrial radiation
  (230 Wm-2).

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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.

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The contribution of short UV to the synthesis of
nucleotides in different radiation conditions
Flight data (MIR)
UV 145
UV 254
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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
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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)

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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

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Basalt mineral composition
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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
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Interaction of montmorillonite ((Na,K,Ca)(?l,Fe,?g
)(Si,Al)4O10(OH)2nH2O) catalytic sites and
organic molecules
? 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) ? Activation of functional groups of
monomers. Adsorption on the clay favors reaction
between monomers. ? The release of oligomers
from the mineral surface. Final reaction
involves two neighbor activated molecules.
From Ferris
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Molecular cloud
Azo-dyes based supermolecules of fullerene
(ErSc2N_at_CH2CH2NHC80, 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
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• 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

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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 photoncm-2s-1.
• At the orbit intensity of solar radiation for 6
  eV photons is 91015 photoncm-2s-1. Hence the
  amount of radiation gained at the orbit during
  two weeks flight is equal to the 2106 years long
  interstellar flight.

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Components in carbonaceous chondrites (in ).
1) Allende meteorite (CV3) 2) Murchison
meteorite powder ( CM2) 3) Lunar soil
significant micrometeoritic component (similar
to C1 chondrites).
(Rosanov, 1996)