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)

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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)