Sigam o Nitrogênio
FOLLOW THE LIFE
• Solvent
• Biogenic elements
• Source of Free Energy
searches for life within our solar system commonly retreat from a search for life to a search for “life as we know it,” meaning life based on liquid water, a suite of so-called “biogenic” elements (most famously carbon), and a usable source of free energy.
(Chyba & Hand, 2005, p. 34)
FOLLOW THE LIFE
• Follow the water
• Follow the carbon
• Follow the nitrogen
• Follow the energy
• Follow the entropy
• Follow the information
Why Nitrogen?
• N is the fourth more abundant chemically active
element in the Universe
• N is one of the elements (together with N, C, O
and P) entering in the composition of the carrier
of biological information in Earth (DNA)
• N allows the assembling of a number of
complex, heterocyclic, assymetric compounds
• The odd-valence of N compounds introduces
asymmetries, which are a necessary condition for
information storage
Four types of organic
macromolecules
in living systems.
Most of the molecules in the living systems are
water (H2O) and large organic
macromolecules:
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids
Proteins
• “Proteios” – primary
• Long “trains” of amino acids
• Different proteins have different sequence of amino acids
• 20 amino acids used in any organism
• Some provide structure (fingernails, hair)
• Some serve as catalysts
• Enzymes – proteins with catalitic properties
Polymerization
• A polymer is a substance composed of
molecules with large molecular mass
composed of repeating structural units, or
monomers, connected by covalent
chemical bonds. Well known examples of
polymers include plastics and DNA.
http://en.wikipedia.org/wiki/Molecular_masshttp://en.wikipedia.org/wiki/Structural_unithttp://en.wikipedia.org/wiki/Monomerhttp://en.wikipedia.org/wiki/Covalenthttp://en.wikipedia.org/wiki/Chemical_bondhttp://en.wikipedia.org/wiki/Plasticshttp://en.wikipedia.org/wiki/DNA
L-Alanine Glycine
Linked by dehydration reaction
Proteins
• “Proteios” – primary
• Long “trains” of amino acids
• Different proteins have different sequence of amino acids
• 20 amino acids used in any organism
• Some provide structure (fingernails, hair)
• Some serve as catalysts
• Enzymes – proteins with catalitic properties
Proteins (continued)
• Even though there are ~70 amino acids
any known life uses only 20
• Amino acids derived abiotically are a mix
of both “left-handed” and “right-handed”
ones. Biological amino acids are only left-
handed.
Chirality
• Was there a common ancestor for all life?
Biology uses only
left-handed Alanine
Amino acids synthesized in laboratory:
The Miller-Urey-Experiment
FIRST EXPERIMENTAL FORMATION OF BIOLOGICALLY
RELEVANT MOLECULES UNDER PREBIOTIC CONDIDTIONS
Murchison (1969, Australia)
Amino acids found in the space:
The Murchinson Meteorite
Does Chirality come from outer space?
Enantiomeric Excesses in Meteoritic Amino Acids
Pizzarello and Cronin, Geochim. Cosmochim. Acta 64, 329-338 (2000)
-1
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1
2
3
4
5
6
7
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En
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Mechanisms?
Racemization?
Amplification?
Meteorites represent the only extraterrestrial
material which can be studied on Earth !
Volatile fraction:
Insoluble C-fraction:
60-80 % aromatic carbon
highly substituted small
aromatic moieties branched
by aliphatic chains
Murchison (1969, Australia)
Abundances of soluble organic compounds in the Murchison meteorite (Botta & Bada 2002, Sephton 2002, 2004)Compound Class Concentration(ppm)
Amino Acids CM 17-60CI ~5
Aliphatic hydrocarbons >35
Aromatic hydrocarbons 3.3
Fullerenes > 1
Carboxylic acids > 300
Hydroxycarboxylic acids 15
Dicarboxylic acids &
Hydroxydicarboxylic acids 14
Purines & Pyrimidines 1.3
Basic N-heterocycles 7
Amines 8
Amides linear > 70
cyclic > 2
Alcohols 11
Aldehydes & Ketones 27
Sulphonic acids 68
Phosphonic acids 2
Difficulties of the organic synthesis
via Meteorites
• Simple organics only – no
macromolecules
• It is hard to accumulate necessary mass of
carbon for the “concentrated” prebiotic
soup.
Building Macromolecules:
Polymerization
• Polymerization produces longer molecules
from simple organic molecules
• One type of polymerization is through the
loss of water
Minerals can help polymerization• Organic soup was probably too dilute to form very long
molecules
• Minerals (like clay) can provide a repeating pattern to act as a template for polymerization
• Small organic molecules could have stuck to the mineral surface
Kaolinite
Catalysts in Chemistry
• Suppose chemical reaction:
A + B → AB is a slow reaction
• The same reaction can be accelerated with catalyst (D):
A + D → AD fast step
B + AD → AB + D fast step
The net result is still:
A + B → AB but it is much faster
Some Proteins are Catalysts
• They are the Enzymes - the largest class of proteins.
• They accelerate the rates of several biological reactions
• They are typically named based on the reaction that they catalyze, and have suffixes with the letters -ase. Example:
Protease (e.g. trypsin, carboxypeptidases)
Lactace (hydrolyzes milk sugar)
Nucleic acids (DNA/RNA)
• Deoxyribonucleic acid (DNA), is a
nucleic acid that contains the
(genetic) instructions used in the
development and functioning of all
known living organisms.
• Collection of nucleotides linked
together in long polymers – the
largest macromolecule
http://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Geneticshttp://en.wikipedia.org/wiki/Developmental_biologyhttp://en.wikipedia.org/wiki/Life
Each nucleotide:
1) Five-carbon sugar molecule
2) One or more phosphate groups
3) Nitrogen-containing compound –
nitrogenous base
Nucleotide
Strand
DNA strand DNA strand
A T
T A
G C
C G
Hydrogen bond
(weak)
A can link only with T
G can link only with C
Watson and Crick (1953) realized
that DNA have a double helix.
Two DNA strands are “complimentary”
to each other
DNA vs. RNA
• Deoxyribonucleic acid (DNA) –deoxyribose sugar
• Ribonucleic acid (RNA) – ribose sugar
Four bases:
DNA RNA
A – adenine – A
G – guanine – G
C – cytosine – C
T – thymine U – uracil
Pyrimidines
Nitrogenated Organic Compounds
in Astrobiology
H2O
CO
CO2CH3OH
NH3CS2HCN
SO2
CH4C2H2C2H6H2CO
OCS
MOLECULAR STRUCTURE OF THE COMA
CO+
CO2+
O+
H2O+
H3O+
OH
HI
NH2S2CN
SO
NS
HNC
C2, C3
H2CO CO
Sagittarius B2
Horse Head Nebula
CHO Molecules
Nitrogenated Molecules
(Abundances relative to CN)
Simple Organic Molecules
Using Isotopic Fractionation (D, C13, N15, O18)
to explore production channels
Nitriles
Bell et al. 1997. On the Detection of Cyanodecapentayne,
HC11N, in TMC-1. Astrophys. J. 483, L61–L64
Nitriles
C2N2 – cyanogen
HC3N – cyanoacetylene
HC5N – cyanodiacetylene
CH3CN – acetonitrile
CH2CHCN – acrylonitrile
CH3C3N – methylcyanoacetylene
From Nitriles to
Nitrogen Heterocyclic
Simple heterocyclic compounds
to be aimed in future observations of the
interstellar and circumstellar medium
oxazole pyrrole pyridine
Titan as a Benchmark
Formation of Pyridine in Titan
Produção de Heterocíclicos em Titan
(Krasnopolsky, 2009)
Propenal and Propanal
in Sgr B2(N)
(Hollis et al. 2004)
Formation of pyrrole from butenal
Formation of pyrrole from s-triazine
Formation of pyridine from pyrrole
PAH-Heterocyclic Connection
PAHs: extremamente resistentestempo de sobrivência no ISM ~ 1 Gano
O PAH pode perder hidrogênios, pois a energia necessária para a perda de um átomo de hidrogênio é 4,5 eV
Um parâmetro adicional que descreve um PAH é o seu grau de hidrogenação, αH/C
Desidrogenação de PAHs
Incorporation of
Nitrogen Atoms
into PAHs
(Ricca et al. 2001)
H
C
N
Which PANHs viable?
A PAH Channel for Production of Pyridine
The PAHs have typically ~ 50 C atoms per PAH
Pericondensates with D6h symmetry: C6n²H6n
n=3 C54H18
C54H18 + γ → C54H17 + H
C54H18 + H → C54H17 + H2C54H17 + HCN → C55H18N + γ
C55H18N + C2H2 → C57H19N + H
C57H19N + γ → C54H18 + HC3N
C57H19N + C2H4→ C54H18+ C5H5N
PAHs and PANHs (root PAH C54H18)
Pericondensates with D6h symmetry: C6n²H6n
n=3 C54H18
Channels for Production of Pyridine
Production of pyrrole vs. pyridine
Densidades de Coluna
IRC+10216 (AGB star)
N < 7.3-8.6 x 1012 cm2
CRL 618 (PN)
N < 2.3-2.7 x 1013 cm2
Searchs for Pyridine in the ISM(Charnley et al. 2005)