The Origin Of Life Dual Origin Hypothesis

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Information about The Origin Of Life Dual Origin Hypothesis

Published on May 30, 2008

Author: Water_Xta1

Source: slideshare.net

The Origin of Life: A Dual Origin Hypothesis Heather E. Jordan Bryant Lab, 232 S. Frear The Pennsylvania State University University Park, PA 16802 MICRB 497-B 3/25/2004 http://www.best3dart.com/3d_space_004.jpg

Where did I come from? Cells? Our genes? What did we descend from? Stardust The first life form on Earth Progenote Cenancestor(s) LUCA Are we alone? Nobody knows for sure (but there may be clues!) http://www.sternwarte-ehingen.de/Galerie/SpaceArt.htm

Cells? Our genes? What did we descend from?

Stardust

The first life form on Earth

Progenote

Cenancestor(s)

LUCA

Are we alone?

Nobody knows for sure (but there may be clues!)

Past Attempts to Answer the Question Pagan Folklore http://www.bcimall.org/calendar/JC2000/image/queen_of_heaven_mother_of_earth.jpg

Pagan Folklore

Past Attempts to Answer the Question Pagan Folklore Religion http://www.fredleavitt.com/DayTwo.html

Pagan Folklore

Religion

Past Attempts to Answer the Question Pagan Folklore Religion Spontaneous Generation (Pasteur) Totora, G., Funke, B. and Case, C.. Microbiology: An Introduction . Pg 8. Redwood City: The Benjamin/Cummings Publishing Company. 1995.

Pagan Folklore

Religion

Spontaneous Generation (Pasteur)

Past Attempts to Answer the Question Pagan Folklore Religion Spontaneous Generation (Pasteur) Directed Panspermia (Crick) http://homepage.hispeed.ch/Final-Frontier/Erde.html

Pagan Folklore

Religion

Spontaneous Generation (Pasteur)

Directed Panspermia (Crick)

Vital Force or Vital Farce? Wöhler (1828) accidentally synthesized urea while trying to make Ammonium cyanate (evaporated instead of allowing crystalization @ room temp.) Letter to Berzelius: "I can no longer, so to speak, hold my chemical water and must tell you that I can make urea without needing a kidney, whether of man or dog; the ammonium salt of cyanic acid is urea ". AgCNO + NH 4 Cl  AgCl + NH 4 CNO (Minard, PSARC Presentation)

Wöhler (1828) accidentally synthesized urea while trying to make Ammonium cyanate (evaporated instead of allowing crystalization @ room temp.)

Letter to Berzelius: "I can no longer, so to speak, hold my chemical water and must tell you that I can make urea without needing a kidney, whether of man or dog; the ammonium salt of cyanic acid is urea ".

AgCNO + NH 4 Cl  AgCl + NH 4 CNO

The Miller-Urey Experiment Original: H 2 H 2 O NH 3 CH 4 Modified Experiments: CO CO 2 CH 2 =CH 2 HC = CH N 2 HCN http://ircamera.as.arizona.edu/NatSci102/lectures/lifeform.htm Energy Sources: Photochemical Shock waves Heat Electrical Products: Amino Acids Nitrogenous Bases Aldehydes Alcohols Hydrocarbons Amines 3-6 C Sugars Esters Carboxylic Acids Amides Ketones Ethers HCN, CO, CO2, H2O2, H2CO3, NH2CONHCONH2, etc.

Original:

H 2

H 2 O

NH 3

CH 4

Modified

Experiments:

CO

CO 2

CH 2 =CH 2

HC = CH

N 2

HCN

Energy Sources:

Photochemical

Shock waves

Heat

Electrical

Products:

Amino Acids

Nitrogenous Bases

Aldehydes

Alcohols

Hydrocarbons

Amines

3-6 C Sugars

Esters

Carboxylic Acids

Amides

Ketones

Ethers

HCN, CO, CO2, H2O2, H2CO3, NH2CONHCONH2, etc.

The Biochemistry of Titan (Maybe?) Protection of Organic Polymers : Thick Atmosphere Saturn’s Cosmic Rays & e-s + Solar UV : N 2 + CH 4  free radicals Yield : Hydrocarbons, Acetylene, HCN (& polymers) Drifts down to the lunar surface Extreme Cold (-178 o C) Liquid H 2 O could result transiently from: Volcanic Activity Impacts Heat could also be provided for reactions this way NH 3 is an antifreeze for H 2 O (pooled on surface) (Lunine, http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=183)

Protection of Organic Polymers :

Thick Atmosphere

Saturn’s Cosmic Rays & e-s + Solar UV : N 2 + CH 4  free radicals

Yield : Hydrocarbons, Acetylene, HCN (& polymers)

Drifts down to the lunar surface

Extreme Cold (-178 o C)

Liquid H 2 O could result transiently from:

Volcanic Activity

Impacts

Heat could also be provided for reactions this way

NH 3 is an antifreeze for H 2 O (pooled on surface)

The Biochemistry of Titan (Maybe?) Protection of Organic Polymers : (Lunine, http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=183) O from liquid H 2 O is donated to hydrocarbon chains on surface Heat Dissipates Organics are deep-frozen & preserved Additional shielding from atmosphere http://www.arcadiastreet.com/cgvistas/saturn_050a.htm

Protection of Organic Polymers :

O from liquid H 2 O is

donated to hydrocarbon

chains on surface

Heat Dissipates

Organics are deep-frozen

& preserved

Additional shielding from

atmosphere

Strecker Synthesis The methane and nitrogen in the atmosphere reacted to form hydrogen & hydrogen cyanide CH 4 + N 2  2 HCN + 3H 2 The hydrogen cyanide in turn, reacted with the formaldehyde HCN + HCHO  H 2 N-CH 2 OH Other products resulted from this H 2 N-CH 2 OH  HN=CH 2 + H 2 O HN=CH 2 + HCN  H 2 NCH 2 CN H 2 NCH 2 CN + H 2 O  H 2 NCH 2 COOH + NH 3 HCN + NH 3  Adenine Successive wetting & freeze-drying under UV Clusters of HCN formed 5-member ring

The methane and nitrogen in the atmosphere reacted to form hydrogen & hydrogen cyanide

CH 4 + N 2  2 HCN + 3H 2

The hydrogen cyanide in turn, reacted with the formaldehyde

HCN + HCHO  H 2 N-CH 2 OH

Other products resulted from this

H 2 N-CH 2 OH  HN=CH 2 + H 2 O

HN=CH 2 + HCN  H 2 NCH 2 CN

H 2 NCH 2 CN + H 2 O  H 2 NCH 2 COOH + NH 3

HCN + NH 3  Adenine

Successive wetting & freeze-drying under UV

Clusters of HCN formed 5-member ring

Incredible HCN! Other purines & pyrimidines produced in smaller amounts Strecker Synthesis also forms Gly HCN spontaneously polymerizes xHCN HCN x 2 Forms : (Polymerization?) Orange (water soluble) Black (water insoluble) Acid hydrolysis 20%+ amino acids Mostly Gly Trace Ala, Asp, Glu, Ser, β-Ala & α-amino isobutyric acid. Urea, Adenine & more! Base Catalyst (Minard, HCN Photos)

Other purines & pyrimidines produced in smaller amounts

Strecker Synthesis also forms Gly

HCN spontaneously polymerizes

xHCN HCN x

2 Forms : (Polymerization?)

Orange (water soluble)

Black (water insoluble)

Acid hydrolysis

20%+ amino acids

Mostly Gly

Trace Ala, Asp, Glu, Ser, β-Ala & α-amino isobutyric acid.

Urea, Adenine & more!

Great but, how else can they be protected from degradation? Preserved by absorption into minerals (meteorites!) Amino Acids Diversity : Miller-Urey (30+ in original, 90+ in variations) Murchison (69+) HCN x (7)

Preserved by absorption into minerals (meteorites!)

Amino Acids Diversity :

Miller-Urey (30+ in original, 90+ in variations)

Murchison (69+)

HCN x (7)

Biological Triad 3 elements are required by life: Water Energy Atmosphere Which planets/moons in our solar system have these elements? Titan 2/3 (very little water) Mars, Ganymede, Europa, Callisto Have complete triad http://solarsystem.dlr.de/polarlander/msss/mars_relay/mars2earth/

3 elements are required by life:

Water

Energy

Atmosphere

Which planets/moons in our solar system have these elements?

Titan

2/3 (very little water)

Mars, Ganymede, Europa, Callisto

Have complete triad

Biological Triad Ganymede Light Atmosphere : H, O 2 , CO 2 & traces H corona Embedded in Jupiter’s magnetosphere (intense radiation & charged particles) Ozone at the poles (e-s travel along field lines & hit polar ice) Europa Light Atmosphere : H, O 2 , CO 2 & traces Significant O 2 levels in atmosphere (HST emission measurements) Embedded in Jupiter’s magnetosphere (intense radiation & charged particles) Callisto Light Atmosphere : H, O 2 , CO 2 & traces H corona Embedded in Jupiter’s magnetosphere (intense radiation & charged particles) http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/Melissa_Smith/Moons.htm http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=713

Ganymede

Light Atmosphere : H, O 2 , CO 2 & traces

H corona

Embedded in Jupiter’s magnetosphere (intense radiation & charged particles)

Ozone at the poles (e-s travel along field lines & hit polar ice)

Europa

Light Atmosphere : H, O 2 , CO 2 & traces

Significant O 2 levels in atmosphere (HST emission measurements)

Embedded in Jupiter’s magnetosphere (intense radiation & charged particles)

Callisto

Light Atmosphere : H, O 2 , CO 2 & traces

H corona

Embedded in Jupiter’s magnetosphere (intense radiation & charged particles)

Planetary Atmospheres Venus CO 2 96.0% N 2 3.5% H 2 O trace Mars CO 2 95.0% N 2 3.0% O 2 /H 2 O trace Earth Signature of Life? N 2 78.1% O 2 21.0% Ar 0.9% H 2 O 0.1-3.0% CO 2 0.03% http://lithops.as.arizona.edu/~jill/EPO/Posters/VenusEarthMars/VEM.jpg

Venus

CO 2 96.0%

N 2 3.5%

H 2 O trace

Mars

CO 2 95.0%

N 2 3.0%

O 2 /H 2 O trace

Earth Signature of Life?

N 2 78.1%

O 2 21.0%

Ar 0.9%

H 2 O 0.1-3.0%

CO 2 0.03%

The Parsimonious Conclusion Currently, most think that early Earth’s atmosphere was composed primarily of CO 2 & N 2 "This type of atmosphere is neutral for oxidation and reduction reactions and does not allow an easy and direct formation of long chains of organic molecules,“ ( Jonathan I. Lunine, University of Arizona planetary sciences Professor). http://ircamera.as.arizona.edu/NatSci102/lectures/lifeform.htm *http://ucsu.colorado.edu/~sbrooks/impacts.html

Currently, most think that early Earth’s atmosphere was composed primarily of CO 2 & N 2

"This type of atmosphere is neutral for oxidation and reduction reactions and does not allow an easy and direct formation of long chains of organic molecules,“ ( Jonathan I. Lunine, University of Arizona planetary sciences Professor).

The Parsimonious Conclusion Large moons of giant, Jovian planets are likely to have thick atmospheres Proximity of moons to giants provides a source for various gasses Simulations of KBO impacts demonstrate why Titan was the only large moon to retain a thick atmosphere in our solar system * Escape Velocities: Titan-Saturn: 35.489 km/s Ganymede-Jupiter: 2.74 km/s Europa-Jupiter: 2.02 km/s Callisto-Jupiter: 2.45 km/s *http://ucsu.colorado.edu/~sbrooks/impacts.html http://www.croastro.com/halloffame/halloffame.htm

Large moons of giant, Jovian planets are likely to have thick atmospheres

Proximity of moons to giants provides a source for various gasses

Simulations of KBO impacts demonstrate why Titan was the only large moon to retain a thick atmosphere in our solar system *

Escape Velocities:

Titan-Saturn: 35.489 km/s

Ganymede-Jupiter: 2.74 km/s

Europa-Jupiter: 2.02 km/s

Callisto-Jupiter: 2.45 km/s

The Parsimonious Conclusion The “Miller-Urey” atmosphere did not exist on Earth (not enough CH 4 to make the organic precursors) Earth was seeded with organics from space (asteroids & comets) Must have been many small impacts of organic-rich material (and 1 really big one?) What types of molecules could have fallen here? http://ircamera.as.arizona.edu/NatSci102/lectures/lifeform.htm

The “Miller-Urey” atmosphere did not exist on Earth (not enough CH 4 to make the organic precursors)

Earth was seeded with organics from space (asteroids & comets)

Must have been many small impacts of organic-rich material (and 1 really big one?)

What types of molecules could have fallen here?

The Origin of Organic Molecules Starting Materials: Methane Nitrogen Formaldehyde Water http:// nolswf.bbc.net.uk/science/space/life/looking/titan.shtml From a moon or planet with a reducing atmosphere : A dead solar system (?) Thick atmosphere of NH 3 , CH 4 & N 2 Covered in tar and formaldehyde

Starting Materials:

Methane

Nitrogen

Formaldehyde

Water

From a moon or planet with a reducing atmosphere : A dead solar system (?)

Thick atmosphere of NH 3 , CH 4 & N 2

Covered in tar and formaldehyde

* CRASH!!! * Frozen organic planet (Mars-sized?) crashes into Earth 4.5 bya Earth crust melts on impact but much debris is scattered in space (some of which forms the moon) Earth cools & crust re-forms Atmosphere restored via geothermal processes http://www.donaldedavis.com/2002_addons/MOONFORM.jpg http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=111

Frozen organic planet (Mars-sized?) crashes into Earth 4.5 bya

Earth crust melts on impact but much debris is scattered in space (some of which forms the moon)

Earth cools & crust re-forms

Atmosphere restored via geothermal processes

* CRASH!!! * Many asteroids fall to Earth, carrying organics from the invading body Organics are concentrated at the surface but protected from degradation until erosion releases them from the rocks. http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=111

Many asteroids fall to Earth, carrying organics from the invading body

Organics are concentrated at the surface but protected from degradation until erosion releases them from the rocks.

Any planets orbiting α-Centauri A or B; 4.35 ly away may have worked their way into the Oort cloud surrounding that system Both stars are ~ 5-6 billion years old All 3 stars of the triad are older than our sun and 1 of them (closest) is a brown dwarf (Proxima) Proxima is spectral type M5 This star has a MS lifespan of 2 x 10 12 years ( 1 st generation! ) Stars in any given region of the galaxy tend to be about the same age so… where are Proxima’s solar siblings? Is the material in our solar system (including pre-biotic organics) leftover from the event that created α-Centauri A & B? http://homepage.sunrise.ch/homepage/schatzer/Alpha-Centauri.html http://www.wncc.cc.ne.us/courses/aveh/lecture/lecevol.htm#Appendix

Any planets orbiting α-Centauri A or B; 4.35 ly away may have worked their way into the Oort cloud surrounding that system

Both stars are ~ 5-6 billion years old

All 3 stars of the triad are older than our sun and 1 of them (closest) is a brown dwarf (Proxima)

Proxima is spectral type M5



This star has a MS lifespan of 2 x 10 12 years ( 1 st generation! )

Stars in any given region of the galaxy tend to be about the same age so… where are Proxima’s solar siblings?

Is the material in our solar system (including pre-biotic organics) leftover from the event that created α-Centauri A & B?

How plausible is this? Pluto, Quaoar (kwa-whar) & Sedna Sedna is 0.014 ly from sun Oort cloud extends 3 ly from sun Oort clouds of other stars can perturb it. Captured from another solar system? http://science.nasa.gov/headlines/y2004/16mar_sedna.htm?list799130

Pluto, Quaoar (kwa-whar) & Sedna

Sedna is 0.014 ly from sun

Oort cloud extends 3 ly from sun

Oort clouds of other stars can perturb it.

Captured from another solar system?

Precious Cargo Body exposed to a supernova shockwave  Propulsion! May not have traveled far… May have been in our own cosmic backyard! http://www.aetheronline.com/mario/AIG/1999+2000/Tantalis.htm

Body exposed to a supernova shockwave  Propulsion!

May not have traveled far…

May have been in our own cosmic backyard!

The Chirality Riddle More L-amino acids in Murchison & Murray meteorites Extraterrestrial cause Neutron star synchrotron radiation from supernova Circularly polarized radiation (Counterclockwise from the star's northern hemisphere and clockwise from the south  chiral radiation!) Polarization too low http://pauillac.inria.fr/algo/vandenbogaert/Proteins/

More L-amino acids in Murchison & Murray meteorites

Extraterrestrial cause

Neutron star synchrotron radiation from supernova

Circularly polarized radiation (Counterclockwise from the star's northern hemisphere and clockwise from the south  chiral radiation!)

Polarization too low

The Chirality Riddle High circular polarizations in star-forming regions of reflection nebulae Orion OMC1 (a region in the Orion nebula M42) NGC 6334. http://www.ast.cam.ac.uk/AAO/local/www/jab/astrobiology/chirality.html/ http://www.sternwarte-ehingen.de/Galerie/SpaceArt.htm

High circular polarizations in star-forming regions of reflection nebulae

Orion OMC1 (a region in the Orion nebula M42)

NGC 6334.

The Chirality Riddle High circular polarizations in star-forming regions of reflection nebulae Orion OMC1 (a region in the Orion nebula M42) NGC 6334. Prediction : “Circular polarization should also be present at the UV wavelengths needed for asymmetric photolysis of molecules such as amino acids.” Our own solar system may have formed in a region of high circular polarization http://www.ast.cam.ac.uk/AAO/local/www/jab/astrobiology/chirality.html/ Anglo-Australian Telescope IR Image Highest circular polarization in white

High circular polarizations in star-forming regions of reflection nebulae

Orion OMC1 (a region in the Orion nebula M42)

NGC 6334.

Prediction : “Circular polarization should also be present at the UV wavelengths needed for asymmetric photolysis of molecules such as amino acids.”

Our own solar system may have formed in a region of high circular polarization

More stuff! Ammonia (imported) + water vapor (native)  hydroxyl acids H 2 S gas (UV absorbing gas) + lightning  cysteine Possibly over 90 other amino acids (imported) Same processes that synthesized also degraded them Aldehydes & cyanides continued to react http://www.arcadiastreet.com/cgvistas/venus_030a.htm

Ammonia (imported) + water vapor (native)  hydroxyl acids

H 2 S gas (UV absorbing gas) + lightning  cysteine

Possibly over 90 other amino acids (imported)

Same processes that synthesized also degraded them

Aldehydes & cyanides continued to react

More organics form… Rocks which preserved imported organics (meteorites) eroded and released them into environment Formaldehyde combined with organics to form sugars and amidinium carbodiimide Catalyzes formation of peptide bonds at 70 o C in dilute solutions http://bizpresenter.corbis.com/search/detail.asp?imageid=11517922

Rocks which preserved imported organics (meteorites) eroded and released them into environment

Formaldehyde combined with organics to form sugars and amidinium carbodiimide

Catalyzes formation of peptide bonds at 70 o C in dilute solutions

High Tide Tides created by the gravitational pull of the moon Cool water rushes in and suspends dried, polymerized organics http://www.sternwarte-ehingen.de/Galerie/spaceart/Space-Art_007.jpg

Tides created by the gravitational pull of the moon

Cool water rushes in and suspends dried, polymerized organics

The Moon Washed organics onto rocks (mostly iron with some zinc, etc.) like pyrite Bound there & aligned by charge Zn facilitated polymerization Most fell apart but a few didn’t Baked under UV during the day http://ircamera.as.arizona.edu/NatSci102/lectures/lifeform.htm

Washed organics onto rocks (mostly iron with some zinc, etc.) like pyrite

Bound there & aligned by charge

Zn facilitated polymerization

Most fell apart but a few didn’t

Baked under UV during the day

Sunscreen for Pre-biotic Molecules?! Evolution: 5 classes of chlorophyll-protein complexes share a common ancestor Derived from a large pigment-carrying protein with more than 10 transmembrane spans Complex protects (cell?) against UV light Dissipative chemistry  photosynthesis http://www.hsv.k12.al.us/schools/middle/wtms/student/cell/cell_energy.html Mulkidjanian, A.Y. & Junge, W. (1997) On the origin of photosynthesis as inferred from sequence analysis. Photosynthesis Research 51:27-42.

Evolution:

5 classes of chlorophyll-protein complexes share a common ancestor

Derived from a large pigment-carrying protein with more than 10 transmembrane spans

Complex protects (cell?) against UV light

Dissipative chemistry  photosynthesis

The UV-Protector Hypothesis Hypothesis: Monomers of reaction centers were pigment-carrying antenna proteins Evidence: sequence alignments revealed clustered UV-absorbing residues With each other With chlorophyll & cofactor ligands Clusters most highly conserved in RC1 Most ancient (Baymann et al., 2001) Baymann, F., Brugna M., Muhlenhoff, U. & Nitschke, W. (2001) Review: Daddy Where Did PSI Come From? Biochimica et Biophysica Acta 1507: 291-310.

Hypothesis: Monomers of reaction centers were pigment-carrying antenna proteins

Evidence: sequence alignments revealed clustered UV-absorbing residues

With each other

With chlorophyll & cofactor ligands

Clusters most highly conserved in RC1

Most ancient

(Baymann et al., 2001)

Advantages of Clustering ↓ Liklihood of photocleavage by: ↓ Lifetime of the excited state, which then: ↑ Photostability Then: Excitation  pigments (rapid internal conversion to lowest excited singlet state) Thermal energy release & dissipation http://bio.winona.msus.edu/bates/Bio241/images/figure-08-12-2.jpg

↓ Liklihood of photocleavage by:

↓ Lifetime of the excited state, which then:

↑ Photostability

Then:

Excitation  pigments (rapid internal conversion to lowest excited singlet state)

Thermal energy release & dissipation

UV Trapping 3 layers Each α-helix helps pack residues with pigments Increases absorption cross section of the membrane Arrangement helped dissipate energy

3 layers

Each α-helix helps pack residues with pigments

Increases absorption cross section of the membrane

Arrangement helped dissipate energy

Does this make sense? Glycine + Acetate  Protoporphyrin IX Precursors were available to make this Intermediate in heme biosythesis Elasticity of α-helices (where porphyrins are attached) Chlorophyll favored due to lower energy singlet state production (in comparison) Natural selection  crucial component in photosynthesis later http://www.indstate.edu/thcme/mwking/heme-porphyrin.html

Glycine + Acetate  Protoporphyrin IX

Precursors were available to make this

Intermediate in heme biosythesis

Elasticity of α-helices (where porphyrins are attached)

Chlorophyll favored due to lower energy singlet state production (in comparison)

Natural selection  crucial component in photosynthesis later

Lots of chemistry going on it’s all still inanimate… what’s missing ? Chemistry needs a container! Brings reagents together The ocean is too dilute... puddles are too risky… what the heck are all these bubbles? All those white flakes can’t be soap! Polymerization of washed up organics, dried on the shore are reclaimed by the tide & voila! http://ajt.iki.fi/travel/lsm/page4.html http://www.todayinsci.com/cgi-bin/indexpage.pl?http://www.todayinsci.com/3/3_24.htm

Chemistry needs a container!

Brings reagents together

The ocean is too dilute... puddles are too risky… what the heck are all these bubbles? All those white flakes can’t be soap!

Polymerization of washed up organics, dried on the shore are reclaimed by the tide & voila!

The First “Container”? Spontaneously form proteinoid microspheres (electrostatic interactions) Able to take up molecules & have electrical potentials across “membranes” Respond to changes in osmotic pressure High Tide = Dinner time!! http://www.biologie.uni-hamburg.de/b-online/e41/3.htm

Spontaneously form proteinoid microspheres (electrostatic interactions)

Able to take up molecules & have electrical potentials across “membranes”

Respond to changes in osmotic pressure

High Tide = Dinner time!!

Microsphere Meals Phosphate also taken up (some already contained A & sugars)  AMP  ATP Contained up to 250 amino acids Wide variety of proteins & enzymes produced Proteolytic Michaelis-Menten kinetics pH optimum ATPase activity http://tycho.bgsu.edu/~laird/ast305/class/IVC-5.html

Phosphate also taken up (some already contained A & sugars)  AMP  ATP

Contained up to 250 amino acids

Wide variety of proteins & enzymes produced

Proteolytic

Michaelis-Menten kinetics

pH optimum

ATPase activity

Elusive Phosphorus Most P trapped in insoluble minerals Heat from volcanic activity released it into oceans Combined with amino acids  acyl phosphates (in vivo) + phosphoramidates (in vitro) Phosphoric acid  more efficiently catalyzes formation of peptide bonds @ 70 o C http://www.kao.re.kr/~neopat/ne07-1.htm

Most P trapped in insoluble minerals

Heat from volcanic activity released it into oceans

Combined with amino acids  acyl phosphates (in vivo) + phosphoramidates (in vitro)

Phosphoric acid  more efficiently catalyzes formation of peptide bonds @ 70 o C

What a Little Phosphate Can Do Phosphates + Glycerol + Fatty Acids  Phospholipids Clumped together Phospholipid Bilayers  Liposomes Acquired many different solutes while drying Nucleotides! www.bio.davidson.edu/Courses/Molbio/MolStudents/.../Favorite_Molecular_Tool.html

Phosphates + Glycerol + Fatty Acids

 Phospholipids

Clumped together

Phospholipid Bilayers

 Liposomes

Acquired many different solutes while drying

Nucleotides!

Fatty Acids Many different chain lengths 14-C chain had special properties : No large proteins could pass Small enzymes & nucleotides enter but can’t exit! http://animalscience.unl.edu/pomplab/metabolome.htm

Many different chain lengths

14-C chain had special properties :

No large proteins could pass

Small enzymes & nucleotides enter but can’t exit!

Creation of Protocells Microspheres picked up everything … even liposomes ATP + nucleotides  oligonucleotides (inside ingested liposome) Began to base pair with itself  RNA? Ribose : 2 1 -5 1 linkage Liposomes + hollow proteins  “membrane” pores Now oligonucleotides can leave http://www.stc.uniroma2.it/cfmacro/cfmacroindex.htm

Microspheres picked up everything … even liposomes

ATP + nucleotides  oligonucleotides (inside ingested liposome)

Began to base pair with itself  RNA?

Ribose : 2 1 -5 1 linkage

Liposomes + hollow proteins  “membrane” pores

Now oligonucleotides can leave

A Pre -RNA World? RNA is simpler than DNA but still complex Possible RNA precursors: PNA pNA TNA Best candidate http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=189

RNA is simpler than DNA but still complex

Possible RNA precursors:

PNA

pNA

TNA

Best candidate

A Pre -RNA World? PNA Peptide/Polyamide Nucleic Acid L-arabinopyranosyl-(4 1  2 1 ) oligonucleotides Strongest base-pairing system of pentopyranosyl family An HCN Polymer Hybridizes to cDNA, RNA * PNA oligomers Can cause steric hindrance of RT, Telomerase & the Ribosome Uncharged (neither repelled by – charged cell walls nor by high inside – membrane potential Promising for anti-microbial drug development (Dr. B. Minard, PSARC Presentation) Cherny, D.Y., et al. , 1993, Proc. Natl. Acad. Sci. USA 90 , 1667-70; Wittung, P. et al. , 1994, Nature , 368 , 561-63.

PNA

Peptide/Polyamide Nucleic Acid

L-arabinopyranosyl-(4 1  2 1 ) oligonucleotides

Strongest base-pairing system of pentopyranosyl family

An HCN Polymer

Hybridizes to cDNA, RNA * PNA oligomers

Can cause steric hindrance of RT, Telomerase & the Ribosome

Uncharged (neither repelled by – charged cell walls nor by high inside – membrane potential

Promising for anti-microbial drug development

PNA: A self-complimentary Sequence!

A PNA World ‘ T’s attached to aminoethylglycine backbone Bind selectively to ‘A’s of oligos & double-stranded DNA Strand displacement: PNA  A-strand & T-strand (single)  excluded (Dr. B. Minard, PSARC Presentation) Cherny, D.Y., et al. , 1992, Proc. Natl. Acad. Sci. USA 90 , 1667-70;

‘ T’s attached to aminoethylglycine backbone

Bind selectively to ‘A’s of oligos & double-stranded DNA

Strand displacement: PNA  A-strand & T-strand (single)  excluded

A PNA World ‘ T’s attached to aminoethylglycine backbone Bind selectively to ‘A’s of oligos & double-stranded DNA Strand displacement: PNA  A-strand & T-strand (single)  excluded Binding to closed, circular DNA  unwinding of double-helix (1 turn/10bp) DNA.PNA complex: Forms @ low [salt] Kinetically stable & cannot be dissociated by ↑ [salt] up to 500 nM. Arrow = unwound DNA by PNA Cherny, D.Y., et al. , 1992, Proc. Natl. Acad. Sci. USA 90 , 1667-70; ↑ ↓

‘ T’s attached to aminoethylglycine backbone

Bind selectively to ‘A’s of oligos & double-stranded DNA

Strand displacement: PNA  A-strand & T-strand (single)  excluded

Binding to closed, circular DNA  unwinding of double-helix (1 turn/10bp)

DNA.PNA complex:

Forms @ low [salt]

Kinetically stable & cannot be dissociated by ↑ [salt] up to 500 nM.

A T NA World? (L)- α –threofuranosyl-(3 1  2 1 ) oligonucleotide Threose is the sugar Simplest nucleic acid alternative Possible ancestor of RNA Possible protector/regulator of RNA (binds to it) Forms base pairs G = C & T/U=A Informational in anti-parallel Cross-pairs with RNA & DNA A & T nucleobase analogs: 2’-amino-(2’-NH2 TNA) 3’-amino-(3’-NH2 TNA) Bst PolI, bacteriophage T7 DNA Pol (exo-) & MMLV-RT Chaput, J.C., Ichida, J.K & Szostak, J.W. (2002) DNA Polymerase-Mediated DNA Synthesis on a TNA Template . J. AM. CHEM. SOC. 125, 856-857.

(L)- α –threofuranosyl-(3 1  2 1 ) oligonucleotide

Threose is the sugar

Simplest nucleic acid alternative

Possible ancestor of RNA

Possible protector/regulator of RNA (binds to it)

Forms base pairs

G = C & T/U=A

Informational in anti-parallel

Cross-pairs with RNA & DNA

A & T nucleobase analogs:

2’-amino-(2’-NH2 TNA)

3’-amino-(3’-NH2 TNA)

Bst PolI, bacteriophage T7 DNA Pol (exo-) & MMLV-RT

A T NA World? Easily forms hairpins much more stable to hydrolytic cleavage than are RNAs and may be as stable as DNAs TNA strands can be synthesized by template-controlled ligation with either complementary TNA or RNA strands as templates corresponding formation of RNA sequences by ligation on a TNA template does also occur, although with less efficiency http://www.scripps.edu/research/sr2001/chm03.html

Easily forms hairpins

much more stable to hydrolytic cleavage than are RNAs and may be as stable as DNAs

TNA strands can be synthesized by template-controlled ligation with either complementary TNA or RNA strands as templates

corresponding formation of RNA sequences by ligation on a TNA template does also occur, although with less efficiency

RNA Replication Sequence that allowed it to copy itself Not advantageous in itself unless– the sequence copied has some advantageous parts in it. More protocells with L-amino acids than R so more D-sugars were used http://www.esb.utexas.edu/jdudley/bio330/quicktime%20and%20avi%20files.htm

Sequence that allowed it to copy itself

Not advantageous in itself unless– the sequence copied has some advantageous parts in it.

More protocells with L-amino acids than R so more D-sugars were used

The Protonucleus Did not originally divide Streamed through pores, filled up cell & inhibited metabolism Clogged pores  breakdown of liposome/protonucleus http://www.botany.hawaii.edu/faculty/webb/BOT410/anatweb/pages/ORNuc-4.htm

Did not originally divide

Streamed through pores, filled up cell & inhibited metabolism

Clogged pores  breakdown of liposome/protonucleus

The Protonucleus Ribozymes Excised fragments of RNA (introns?) Crowded protonucleus burst 2 tangles of folded RNA (replicated) Intron scraps http://ndbserver.rutgers.edu/NDB/NDBATLAS/P/pr0005/pr0005_1_gif.html U1A SPLICEOSOMAL PROTEIN/HEPATITIS DELTA VIRUS GENOMIC RIBOZYME COMPLEX

Ribozymes

Excised fragments of RNA (introns?)

Crowded protonucleus burst

2 tangles of folded RNA (replicated)

Intron scraps

Protonuclear Division Liposome phospholipids attracted to each other but pushed apart by tangles of RNA Reform encircling RNA (some mistakes, i.e., picking up introns or nothing) RNA folding ensured that everything stuck together (daughter cell received 1 copy) http://www.biologiateorica.it/organiccodes/cap5/p124.htm

Liposome phospholipids attracted to each other but pushed apart by tangles of RNA

Reform encircling RNA (some mistakes, i.e., picking up introns or nothing)

RNA folding ensured that everything stuck together (daughter cell received 1 copy)

Primitive Protocell Metabolism Precursors needed to maintain “membranes” Proteins, lipids & carbohydrates First chemoorganotroph (popular; simple metabolism) Protocells died when starved, became toxic, got too big or in wrong environment Some grew faster than others, made products that facilitated growth, etc. http://www.funhousefilms.com/sciencpg.htm

Precursors needed to maintain “membranes”

Proteins, lipids & carbohydrates

First chemoorganotroph (popular; simple metabolism)

Protocells died when starved, became toxic, got too big or in wrong environment

Some grew faster than others, made products that facilitated growth, etc.

Fortunate mistakes RNA has a high error rate Enough nucleic acid precursors? Multi-protonuclei Less nutrients coming in & available (volume increased faster than surface area) Few cells acquired a mutation that provided the protocell with a cytoskeleton Contracted along equatorial plane in response to diminished nutrient levels Cleaved cell & split up protonuclei http://image.bloodline.net/stories/storyReader$1349

RNA has a high error rate

Enough nucleic acid precursors?

Multi-protonuclei

Less nutrients coming in & available (volume increased faster than surface area)

Few cells acquired a mutation that provided the protocell with a cytoskeleton

Contracted along equatorial plane in response to diminished nutrient levels

Cleaved cell & split up protonuclei

So… what is it? Self-replicating, Gram negative chemoorganotroph with ability to pass on genetic information to progeny Competition: Food Advantageous mutations  Zn-containing polymerases (from washing on rocks & still used today) http://www.bact.wisc.edu/bact330/lecturestaph

Self-replicating, Gram negative chemoorganotroph with ability to pass on genetic information to progeny

Competition:

Food

Advantageous mutations  Zn-containing polymerases (from washing on rocks & still used today)

A Cenancestor? Retention of favorable mutations required higher fidelity DNA (with deoxyribose, now have 5 1 -3 1 linkage) But RNA not completely out of the picture (just in different niches as it diversified) Ribosomes from protonucleus? Viruses still have the protein coats (lost genes?) Genome shortened as it took up residence in larger protocells  faster replication top priority http://www.braum.de/2001/thomas/hintergrundbilder/1024/Virus.jpg

Retention of favorable mutations required higher fidelity

DNA (with deoxyribose, now have 5 1 -3 1 linkage)

But RNA not completely out of the picture (just in different niches as it diversified)

Ribosomes from protonucleus?

Viruses still have the protein coats (lost genes?)

Genome shortened as it took up residence in larger protocells  faster replication top priority

But… there is one other possibility! The first life form may have been photosynthetic! You’re kidding, right? http://www.bact.wisc.edu/bact330/lecturestaph

The first life form may have been photosynthetic! You’re kidding, right?

What is agreed upon Anaerobic environment 1 st photosynthesizers used H 2 or H 2 S as substrates Microbes still do this (H 2 S  H 2 + S) Purple & green sulfur bacteria PSI has 11 transmembrane domains http://bio.winona.msus.edu/bates/Bio241/images/figure-08-12-2.jpg

Anaerobic environment

1 st photosynthesizers used H 2 or H 2 S as substrates

Microbes still do this (H 2 S  H 2 + S)

Purple & green sulfur bacteria

PSI has 11 transmembrane domains

UV-Protector  Energy Producer Mutations that prevented chlorophyll binding Cavity exposed charges of ligands Attracted cofactors (FeS complexes/quinones) Re-stabilized the polypeptide ↑ UV absorbance & dissipation Mutations : Gene fission Loss of α-helical domains (1 o e- binding site)

Mutations that prevented chlorophyll binding

Cavity exposed charges of ligands

Attracted cofactors (FeS complexes/quinones)

Re-stabilized the polypeptide

↑ UV absorbance & dissipation

Mutations :

Gene fission

Loss of α-helical domains (1 o e- binding site)

Exhibit A: Careful! It’s 3.5 billion years old! 3.5 billion year-old cyanobacteria-like fossils Already photosynthesizing Pigment-carrying antenna protein may have evolved concurrently with life 200 million-year window from the solidification of Earth’s crust & this fossil! Much of this time, too warm for the right chemistry so… http://www.ucmp.berkeley.edu/historyoflife/mysteries/mystery9/mystery9.html

3.5 billion year-old cyanobacteria-like fossils

Already photosynthesizing

Pigment-carrying antenna protein may have evolved concurrently with life

200 million-year window from the solidification of Earth’s crust & this fossil!

Much of this time, too warm for the right chemistry so…

 

Acknowledgements Dr. Bob Minard Dr. Greg Ferry Dr. John Golbeck Sabrina Zimmerman

Dr. Bob Minard

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