ORIGINE DEL MATERIALE GENETICO SU PARTICELLE

MINERALI

Enzo GalloriDBAG- Università di Firenze

Erwin Schrödinger

• “What is Life”, 1944

The DNA Molecule

Pu

Py

Adenine (A)

Guanine (G)Thymine (T)

Cytosine (C)

Phosphate

Sugar

Base

Nucleotide

The Transition from Chemistry to Biology:Nucleic Acids (DNA, RNA) as

Stores of Biological InformationComplementary

Base Pairing

A = T

G C

“Genetic Information

”A

G

A T

G C

T

C

DNA

The basic principle of biology

Replication

Transcription

Genotype

Traduction

Phenotype

G

A

A

G

Perpetuation of Information

A

G

T

C

A

G

T

C

T

C

T

C

Replication

A

G

A T

G C

T

C

A

G

A T

G C

T

C

Building Code

• Synthesis and accumulation of precursors (i.e. nucleotides)

• Joining of precursors into larger molecules (i.e. DNA, RNA)

• Protection from degradation Persistence

• Expression of biological “potentiality” of the informational molecule

Prebiotic Chemistry

Synthesis and Accumulation of Precursors:

A.I. Oparin (~1920) - J.B.S. Haldane (~1930)

““The Primordial Soup”The Primordial Soup”

S.L. Miller (1953)

“Primordial” Soup

Refrigerator

Electrodes

Cosmic

radiation

Molecules from Space

Synthesis and Accumulation of Precursors:

Amminoacids

Ethers

PAH

N Bases ?

H,

CO,

PAH

Diffuse Clouds

Ice :

Core

H

CH

CO

PAH

Dense Clouds

Early Earth

CometsMeteorites

Chemistry in Cosmic DustLaboratory simulations (L.J.Allamandola and coll., 1995-2000)

Water

Carbon monoxideCarbon dioxide

Methanol

Hydrocarbon

Silicate granuleIce

•Ketons

•Aminoacids

•Quinones

•N Bases?

U.V. radiation

Building Code

• Synthesis and accumulation of precursors (i.e. nucleotides)

• Joining of precursors into larger molecules (i.e. DNA, RNA)

• Protection from degradation Persistence

• Expression of biological “potentiality” of the informational molecule

• Ricerca classica: Chimica in soluzione acquosa

Polimerizzazione

In queste condizioni: è favorita

l’idrolisi e non la polimerizzazione.

Chimica su superficie minerale Argille

J.D. Bernal (1951)

“. . . clays and other minerals were necessary to:

1) Concentrate the organics present in a dilute ocean by adsorption;

2) Protect these organics from destruction by U.V. light;

3) Catalyze the polymerization of adsorbed organics . . . ”

• May catalyze the formation of oligonucleotides and peptides up to 50-mer long

Ertem and Ferris (1996), Nature 379: 238-240

Ferris et al. (1996), Nature 381: 59-61

Joining of precursors into larger molecules: Mineral surfaces

A CA T

AG

G TGC

AC

A

Nucleic acid-clay complexes

RNADNA

Clay minerals:montmorillonite (M)kaolinite (K)

Clay minerals:montmorillonite (M)kaolinite (K)

Electron Microscopy (T.E.M.)

K-Chromosomal DNA(X 154,000)

K-Plasmid DNA(X 271,500)

Franchi et al., 1999, OLEB 29: 297-315Franchi et al., 1999, OLEB 29: 297-315

X-Ray Analysis of M-nucleic acid complexes

2 7 12 17 22 27 32 37 42 472

M

M-DNA

M-RNA

Franchi et al., 1999, OLEB 29: 297-315Franchi et al., 1999, OLEB 29: 297-315

Role of cations in theadsorption of nucleic acids

0,0%

10,0%

20,0%

30,0%

40,0%

50,0%

60,0%

70,0%

80,0%

90,0%

100,0%

0,1 1 10 100[Ca2+] (mM)

Ad

so

rpti

on

%

0

2,5

5

7,5

10

12,5

15

17,5

20

22,5

25

Am

ou

nt

Ad

so

rbe

d (

µg

/mg

of

cla

y)

ss-Poly[A] ds-DNA

FT-IR Analysis

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45

0,5

1800

1750

1700

1650

1600

1550

1500

1450

1400

1350

1300

1250

(cm-1)

Abs

orba

nce

free DNAK-adsorbed

DNA

kaolinite

Franchi et al., 1999, OLEB 29: 297-315Franchi et al., 1999, OLEB 29: 297-315

Resistenza degli Acidi Nucleiciadsorbiti all’argilla

La forrmazione dei dimeri di Timina è ridotta nel caso del DNA adsorbito all’argilla

Gallori et al., (2004)

U.V. radiation

K-Chromosomal DNA(X 154,000)

Did stone nurture the first life on earth?