Astrobiology, Astrobiology, homochirality, and homochirality, and origins of life origins of life Int. J. Astrobio. Int. J. Astrobio. 3 3 , 209 (2004), , 209 (2004), 4 4 , 75 , 75 (2005), (2005), Orig. Life Evol. Biosph. Orig. Life Evol. Biosph. 35 35 , 225 (2005), , 225 (2005), 35 35 , , 507 (2005) 507 (2005) The four corner stones of astrobiology Astrobiology in Nordic countries Role of Nordita Our current interests: homochirality and origin of life peptide world, RNA world Pencil Code Community effort Suitable for distributed systems
Astrobiology, homochirality, and origins of life. The four corner stones of astrobiology Astrobio logy in Nordic countries Role of Nordita Our current interests: homochirality and origin of life peptide world, RNA world Pencil Code Community effort Suitable for distributed systems. - PowerPoint PPT Presentation
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Astrobiology, homochirality, Astrobiology, homochirality, and origins of lifeand origins of life
Int. J. Astrobio. Int. J. Astrobio. 33, 209 (2004), , 209 (2004), 44, 75 (2005),, 75 (2005),Orig. Life Evol. Biosph. Orig. Life Evol. Biosph. 3535, 225 (2005), , 225 (2005), 3535, 507 (2005), 507 (2005)
• Early life– Extremophiles– Cyanobacteria– Oxygen, methane evol.– LUCA
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Onset of lifeOnset of life
• There is no good definition of life– replication (birth/death), evolution, metabolism– Protolife (simplistic): 2H2+CO2 (CH2O)+H2O– Ignores waste produced: CH4 , H3C-COOH, or O2
– Ignores replication machinery
• Hypothesis: primitive life is unavoidable– Several independent geneses of life on early Earth?– No serious competitors to carbon-based life
Aminoacids in proteins: left-handedAminoacids in proteins: left-handedSugars in DNA and RNA: right-handedSugars in DNA and RNA: right-handed
Louis PasteurLouis Pasteur(1822-1895)(1822-1895)
animoanimogroupgroup
carboxylcarboxylgroupgroup
chlorophyllchlorophyll
Is chirality:Is chirality:(i) prerequisite(i) prerequisite
• Life only develops in homochiral environment– Homochirality is then a prerequisite
• However: no mechanism produces 100% e.e.– only minute partial excess possible (electroweak)– slightly bigger for large Z, goes like Z5 Cu (II) ions
• Still need amplification mechanism– Frank (1953) model (plus extensions): nucleotides– Autocatalysis and enantiomeric cross inhibition– Plasson, Bersini, Commeyras (2004): peptides
14
Chirality selection during polymerizationChirality selection during polymerizationof the first replicating molecule?of the first replicating molecule?
RR
LL
Isotactic polymer (same chirality)
“waste” (enantiomericcross-inhibition)
dual worlddual worldRNA worldRNA worldPNA worldPNA worldlipid worldlipid world
RNARNARNARNADNADNA
proteinsproteins
Rasmussen et al (2003Rasmussen et al (2003Artif. LifeArtif. Life 99, 269-316), 269-316)
achiralachiral
chiralchiral
PolymerizationPolymerization
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Exponential amplificationExponential amplificationrecap of Frank-type model (Frank 1953)recap of Frank-type model (Frank 1953)
auto-catalysis aloneauto-catalysis alone
LLLS
DDDSk
k
LS
DSL
D
]][[d
][d
]][[d
][d
LSkt
L
DSkt
D
C
C
kinetic equationkinetic equation
enantiomeric excess:enantiomeric excess:
const.][[D]
][-[D]
][[D]
][-[D]e.e.
00
00
L
L
L
L
][
e[L][L]
e[D][D]
0
0
SkC
t
t
exponentialexponentialgrowthgrowth
catalystcatalyst
16
Need also mutual antagonismNeed also mutual antagonism(to siphon off the bad guys)(to siphon off the bad guys)
Proto type: Fisher’s equationProto type: Fisher’s equation
'')1( XXXX
)( ctxfX 2c
wave speedwave speed
wwith Tuomas Multamith Tuomas Multamääki, Int. J. Astrobio. 3, 209 (2004)ki, Int. J. Astrobio. 3, 209 (2004)
Spread of the black Spread of the black deathdeath
LLRLLR
L
dt
dL
RRRLLR
R
dt
dR
222
2
222
2
)(
)(
13501350
13491349
13481348
13471347
26
1D reduced model 1D reduced model (reaction-diffusion equation)(reaction-diffusion equation)
Propagation into racemic environmentPropagation into racemic environment
27
2D model (reaction-diffusion equation)2D model (reaction-diffusion equation)
XX (X-Y)[1-(X-Y)(X-Y)[1-(X-Y)2 2 X-YX-Y]]
28
Piecewise linear increasePiecewise linear increase
29
Piecewise linear increasePiecewise linear increase
SAA
A
t
Ad
1
1
d
d
2
2
SSS 221
ASAAS
ASA 2
22
222
add/subtract:add/subtract:
LRLLR
L
dt
dL
RRLLR
R
dt
dR
)(
)(
22
2
22
2
Reduced equationsReduced equations
trrrr 212
30
Initial e.e. not related to final e.e.Initial e.e. not related to final e.e.
31
3-D and effects of turbulence3-D and effects of turbulence
32
Where could this work?Where could this work?
Braun & Libchaber (2003)Braun & Libchaber (2003)
a) hydrothermal ventsa) hydrothermal vents
b) Deep biosphereb) Deep biosphere
Michael J. RussellMichael J. Russell(2006, Am. Sci. 94, 32-39)(2006, Am. Sci. 94, 32-39)
ideas about firstideas about firstProtocellsProtocells
April 21, 2023
PencilPencilCodeCode
• Started in Sept. 2001 with Wolfgang Dobler• High order (6th order in space, 3rd order in time)• Cache & memory efficient• MPI, can run PacxMPI (across countries!)• Maintained/developed by ~40 people (SVN)• Automatic validation (over night or any time)• Max resolution so far 10243 , 4096 procs• http://pencil-code.googlecode.com
• Sphere embedded in box– Fully convective stars– geodynamo
• Other applications– Homochirality– Spherical coordinates
34
35
36
ConclusionsConclusions• Astrobiology: need to be prepared…
• Polymerization model:– Based on measurable processes
• Reduction to accurate simplified model– Homochirality in space (earth, interstellar, etc)– Timescales 500 Myr; fossil evidence of spatially fragmented
homochirality?
• Pencil Code: just google for it– Detailed manual, …