Abiogenesis: Origin of Life and Compartments

Abiogenesis and Compartments

• Abiogenesis studies how life arose from non-living matter, focusing on the formation of compartments and the origin of information.
• Possible prebiotic compartments existed in both inorganic and organic forms.
• Key questions include how a genotype can generate a phenotype and then create more genotypes.
• Scientists such as Spiegelman, Eigen, and Higgs have contributed to our understanding.

Abiogenesis: Origin of Life

• Evolution starts once life has evolved ie Abiogenesis must happen first.
• Abiogenesis occurs first, and the evolution of life follows, generating diverse life forms.

Protocells and Compartments

• Protocells may have been precursors to life, protecting abiotic reactions.
• Protocells are compartments that isolate abiotic reactions.
• Compartments protect these reactions from the abiotic world and parasites, and confine reactions to the chemical precursors.

Organic Compartments

• Organic compartments form because of competition or stealing of resources and intermediates.
• Coacervates are droplets of complex organic molecules.
• Oparin discovered them in 1924.
• Proteinoids are peptides that assemble into microspheres; Sidney Fox studied these thermal proteins in the 1950s and '60s.
• Liposomes are droplets of lipids which can self assemble into lipid bilayers (Deamer and Oro 1980).

Coacervates and Proteinoids : Problems

• Coacervates present a problem, that they need complex biomolecules to form.
• Proteinoids also need high amino acid concentrations to form, lacking a plausible way for molecules to enter and exit.
• Sutherland's group has approached success with simple lipids, but no success has been seen in producing phospholipids through abiotic ways

Inorganic Compartments and Chemical Reactions

• Inorganic compartments are alternatives to complex biomolecules, offering two or three dimensional "spaces”.
• Inorganic surfaces are often 2D worlds including clays and minerals like iron pyrite FeS2.
• They enhance the polymerization of nucleosides.
• Reactions need high concentrations of reagents and intermediates.
• Surfaces trap reagents/intermediates and promote reactions through concentration.

Surface Isomers and enantiomeric selection

• Initial components could have consisted of just surfaces.
• L-amino acids and D-sugars are selected.
• On the genesis of genomes within inorganic compartments, Koonin and Martin discuss the origin of cells.

3D Inorganic Compartments

• Hydrothermally formed connected iron-sulfide(FeS) compartments contain 1 µm to 100 µm cavities.
• The paper argues that thermal vents are the ideal locations for forming membranes via chemical evolution in such compartments.

Ideas on the Origin of Life

• Metabolism and information are two competing ideas
  • Proteins came first Oparin, Fox and Haldane
  • Nucleic acids came first Orgel and Eigen
• Freeman Dyson proposed the Double Origin Hypothesis in 1999 and life started off as:
  • Two separate "life forms” simple peptides
  • Simple nucleic acid pools.
• Sutherland's 2015 work indicates that both peptides:
  • Nucleic acids could have arisen at the same time.

Freeman Dyson's Double Origin

• Double origin suggests there was/ is symbiosis.
• You need metabolism to support information/replicators.
• Replicators evolved separately.
• Eventually nucleic acids dominated metabolism for their own purpose.

Nucleic acid facts

• Nucleic acids are chronic parasites.
• Modern life forms arise due to nucleic acid infection.
• Dysons first origins
  • Metabolism
  • Viruses
  • Perfect replicators

Cairns-Smith and Clays

• Crystals and clay represent: abiotic "order”.
• The single origin has an inorganic replicator/information:
  • Compartments provide information.
  • Crystal surfaces catalyse and isolate reactions
  • Crystals of clay abiotically provide a scaffold for organizing complexity.

Cairns-smith term

• Cairns-Smith coined the term: "genetic take over"
• Clay minerals are an inorganic replicator that can be catalysts Clay and Proto-cells
• Clay or Proto-cells has to be a precursor to genetics

Clay and Genes

• Clay comes before genes, and provides information that supports metabolism in two dimensions (2D).
• Protein-based "enzymes" are secondary(catalysts).
• Cells in three dimensions (3D) have more efficient protein-based metabolism: Genes are last.
• The blend of minerals plus silicon acts a "charges act as a code"

Minerals and particles

• Silica terahedra sheets bonded by ions.
• Particles are minerals under 1/256mm

Proto-cells and Thermal Vents.

• Microscale caves and rock cavities act as "natures test tubes.
• It starts to form around thermal vents, with "cavities" providing the template for constructing protomembranes.
• There is a high level of thermal energy in them, so they must come about from protongradients

Iron Sulphide Minerals

• Early thermal vents consist of iron sulfide minerals.
• They could form:
  • Membranes and other features needed for bio-energetics
  • They're early catalyst formations
  • Membranes must be easy for H+ / Na+

Jack Szostak and RNA Vesicles

• Jack Szostak said that fatty acids/lips form vesicles that are selective
• RNA combined with day can be useful

Temperate Protocells

• The environment has to provide chemical and physical things that allow perpetuation:
  • "Cool" temperatures with RNA replicaiton
  • Cell/vesicles grow with lipid incorporation
  • "Cell division" in splitting
  • "Hot" separates dsRNA to ssRNA

Orgin of Information and replicatiors

• Nucleic acid replicators are most popular for being self templating
• Eventualy how to make proteins is a key point

Scientists in Replicators

• Spiegelman focused on replication demons - RNA phages that have been shown to replicate outside of a cell
• Eigen worked on catalytic hypercycles
• Higgs focused on system building, needing a catalyszt

Eigen's Hypercycles

• In the 1970s, Eigen focused theorised genes being first.
• He used to create replicatiors

Ancient RNA

• Eigen thought that RNA polymerase didn't need primmers
• Ribose sugars were more common that DNA
• Folding gives shape and shape influences the "phenotype"
• It is able to make other proteins in the similar systems
• Key influences where -Test tube experiments
  • Mathematical/Stat modelings
  • Working under Orgel