Searching for the Origins of Life in Interstellar Space Michael Jarvis & the Research Group of Professor D. K. Bohme Centre for Research in Mass Spectrometry, York University Thursday, April 26, 2007. NGC 4526
What is the chemical composition of our galaxy? Composition of the stars: •90% hydrogen •10% helium •trace amounts of heavy elements Our Sun Composition of interstellar clouds: •gas and dust grains •mostly hydrogen and helium •trace amounts of small molecules (H 2 O, CH 2 O, CH 4 , NH 3 , CO 2 , and CH 3 OH), in gas-phase and on the surface and in the interior of dust grains N H H OH H H H H Horsehead nebula O H H H H H H
In our galaxy, Earth is a very special place. Complex organic molecules are abundant! LIFE is abundant! Earth atmosphere: N 2 (78%) , O 2 (21%) , Ar (0.9%) , CO 2 (0.04%) H 2 O, O 3 , CFCs... Proteins DNA,RNA
What are the fundamental requirements for life? (1) water (2) nucleic acids and amino acids (organic polymers) Topic of this (DNA,RNA) (proteins) presentation. 4-member “Bradykinin”: oligonucleotide arg–pro–pro–gly–phe–ser–pro–phe–arg
Where were organic compounds such as amino acids first formed? On Earth? Elsewhere? There are two (competing) theories: (1) Organic compounds were delivered to Earth by interplanetary dust, meteorites, comets and asteroids: “Panspermia” (2) Organic compounds were synthesized on Earth. The required energy is provided by lightning, UV, cosmic radiation, thermal energy or radioactive decay. “Homegrown synthesis”. “Many of the interstellar molecules discovered to date are the same kinds detected in laboratory experiments specifically designed to synthesize prebiotic molecules. This fact suggests a universal prebiotic chemistry.” - Jan M. Hollis, NASA Goddard Space Flight Centre
Can we “see” molecules in the interstellar medium? The Very Large Array (VLA), consisting of 27 radio antennas on the Plains of San Agustin, New Mexico, is one of the world’s premier astronomical radio observatories. Each antenna is 25 meters in diameter. The planetary nebula K3-35. The colors show the 3.6 cm emission. The various colours represent different intensities of emission.
Radioastronomy is used to identify molecules based on unique “fingerprint” emissions or absorptions. • Molecules rotate end-over-end. • When they change from a higher rotational energy level to a lower rotational level, they emit radio waves (photons) at precise frequencies. A recent discovery: In 2004, glycolaldehyde was discovered in a cold region (8 K) of the gas- and-dust cloud Sagittarius B2, 26,000 light years away, near the centre of our own Milky Way Galaxy. The discovery was made using the National Science Foundation’s giant Robert C. Byrd Green Bank Telescope (GBT). 2-carbon 3-carbon 5-carbon sugar + sugar sugar (ribose) The synthesis of ribose molecules is important because these molecules form the backbone structure of both DNA and RNA, the carriers of all genetic information.
Have amino acids been detected in the interstellar medium? INTERSTELLAR GLYCINE Y.-J. Kuan, S.B. Charnley, et al. Astrophys. J. 593: 848-867 (2003) “…27 glycine lines were detected …in one or more sources..” A RIGOROUS ATTEMPT TO VERIFY INTERSTELLAR GLYCINE L.E. Snyder et al. Astrophys. J. 619: 914-930 (2005) “We conclude that key lines necessary for an interstellar glycine identification have not yet been found.”
Thus, the presence of glycine in the interstellar medium has not yet been confirmed, but the possibility cannot be ruled out… Nonetheless, biological material has been found in ppm quantities in meteorites that have impacted on Earth. • more than 70 different amino acids • carboxylic acids • pyrimidine • purine
The “carbonaceous chondrite” class of meteorites have been found to contain up to 60 ppm of amino acids! CI Chondrites: •cometary origin (material from interstellar medium) CM Chondrites: •asteroidal origin (material from solar system) Amino acid composition in two CI (Ivuna and Orgeuil) and two CM (Murchison* and Murray) meteorites: Amino acid CI(%) CM(%) Glycine 17 17 α -amino acids 17 63 β , γ -amino acids 20 66 Sept. 28, 1969 *More than 70 different amino acids were Murchison, Australia detected in the Murchison meteorite!
In our laboratory we study gas-phase ion chemistry. Why are ion/molecule reactions important in the ISM? • They are largely unaffected by extreme low temperatures (10-20K). • They are ~100 times faster than neutral/neutral reactions. Let’s see if we can generate amino acids from starting materials, involving ions, that are known to exist in the ISM. •gas and dust grains CH + (vis), CF + , CO + , NO + , SO + , H 3 + •mostly hydrogen and helium (IR), HCO + , COH + , HCS + , N 2 H + , H 3 O + , HOCO + , HCNH + , H 2 COH + , HC 3 NH + , •trace amounts of small molecules (H 2 O, C 6 H - , C 4 H - , C 8 H - CH 2 O, CH 4 , NH 3 , CO 2 , and CH 3 OH), in gas-phase and on the surface and in the interior of dust grains N H H OH H H H H O H H H H H H
Selected-ion flow tube/triple quadrupole mass spectrometer (SIFT/QqQ)
“Simulating” the environment of the interstellar medium: • He as a buffer gas. • Pressure of only 0.35 Torr (0.0005 atm). • Reacting ions and molecules have no translational kinetic energy reagent molecules To Roots Blower (variable flow) Analysis and Ions enter quantitation in instrument quadrupole mass spectrometer Fixed reaction time
Several attempts to generate glycine were unsuccessful: + + HCOOH O CH 3 NH 2 + + CO 2 CH 3 NH 2 + + CO + H 2 O NH 2 CH 3 NH 2 + + CH 3 COOH NH 3 OH CH 2 COOH + + NH 3 N-O bond formation is preferred over C-C and N-C bond formation. Success!! NH 2 OH + + CH 3 COOH → NH 2 CH 2 COOH + (ionized glycine) + + CH 3 COOH → NH 3 CH 2 COOH + (protonated glycine) NH 2 OH 2 • OH + O bonding allows N-C bond formation (Blagojevic et al., Mon. Not. R. Astron. Soc. 339 (2003) L7-L11.)
NH 2 OH + + CH 3 COOH → NH 2 CH 2 COOH + Some background on the precursors: + + CO → CH 2 CO + + hv CH 2 Acetic acid: CH 2 CO + + 2H 2 O → CH 3 COOH + + H 2 O Has been detected in ISM (1997) Hydroxylamine: NH 3 (s) + H 2 O(s) + hv → NH 2 OH(g) + other products Nishi et al. (J. Chem. Phys., 80, 3898, 1984) Undetected in ISM (so far) • NH 2 OH will be made in irradiation of interstellar ice (as shown by Nishi et al.). • Charnley et al. (Sept. 2001) proposed that NH 2 OH should be one of the major components of interstellar ice. It can be formed by radical hydrogenation of NO on the surface of dust grains.
Comparing the fragmentation of our product ion with that of commercial (ie. purchased) glycine: 0.8 CH 2 NH + 0.6 0.4 Gly + Relative abundance 0.2 0.0 0.8 Gly + CH 2 NH + • Increasing the voltage on the nose cone 0.6 induces energetic collisions between ions and 0.4 the neutral buffer gas. 0.2 • The specific fragmentation patterns and 0.0 0 5 10 15 20 25 30 35 40 45 appearance energies can be used as a Nose cone potential (/-V) “chemical fingerprint” to identify unknowns.
Computational Chemistry results: (NH 2 OH)H + + CH 3 COOH Δ H 0 , kcal mol -1 Potential energy landscape TS2 for the reaction between protonated hydroxyl amine 24.3 23.1 and acetic acid to produce GlyH + 0.0 -13.7 -18.8 -27.2 B3LYP/6-311++G(df,pd) TS1 -54.1 PRC2 (Galina Orlova) H 2 O
Larger amino acids: Synthesizing alanine Buoyed by our great success synthesizing glycine via a gas-phase ion/molecule reaction, we have attempted to synthesize alanine in a similar manner. NH 2 OH + + CH 3 CH 2 COOH → NH 2 CH 2 CH 2 COOH + (ionized alanine) + + CH 3 CH 2 COOH → NH 3 CH 2 CH 2 COOH + (protonated alanine) NH 2 OH 2 The isomer formed is β -alanine... … this can be confirmed from the observed fragmentation pattern. Biological Non-biological isomer isomer (protonated) (protonated) α -alanine β -alanine
The “carbonaceous chondrite” class of meteorites have been found to contain up to 60 ppm of amino acids! CI Chondrites: •cometary origin (material from interstellar medium) CM Chondrites: •asteroidal origin (material from solar system) Amino acid composition in two CI (Ivuna and Orgeuil) and two CM (Murchison and Murray) meteorites: Amino acid CI(%) CM(%) Glycine 17 17 α -amino acids 17 63 β -alanine 1 40 other β , γ -amino acids 26 19 Sept. 28, 1969 Murchison, Australia
Computational Chemistry results: (NH 2 OH)H + + CH 3 CH 2 COOH Δ H 0 , kcal mol -1 Potential energy landscape for TS2-a TS2-ß TS2-a the reaction between protonated 17.4 hydroxyl amine and propanoic 24.3 acid to produce TS2-ß 12.4 β -AlaH + (solid line) and α - 0.0 AlaH + (dotted line) -14.5 -19.4 -27.2 B3LYP/6-311++(df,pd) TS1 -59.5 -65.3 (Galina Orlova) a-AlaH + ß-AlaH + H 2 O
NH 2 CH 2 COOH NH 2 CH 2 CH 2 COOH M + H e - M NH 3 CH 2 COOH + NH 2 CH 2 COOH + NH 3 CH 2 CH 2 COOH + NH 2 CH 2 CH 2 COOH + CH 3 COOH CH 3 COOH -H 2 O CH 3 CH 2 COOH -H 2 O CH 3 CH 2 COOH hv/A + RH + NH 2 OH + + NH 2 OH NH 2 OH 2 Interstellar gas hv, heat Interstellar ice hv hv NH 3(s) + H 2 O (s) NH 2 OH NO + 3H M and A represent any neutral atom / molecule with a suitable IE. RH + represents a proton carrier with PA(R) < PA(NH 2 OH). (Blagojevic et al., Mon. Not. R. Astron. Soc. 339 (2003) L7-L11.)
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