Protobionts... encapsulated chemical reactivity*   -  "pre-life molecular micelles"
        aggregates of prebiotic molecules  macromolecules that acquire a boundary to maintain
        an interior chemcial environemnt distinct from "primordial soup".   
                 Coacervates - Proteinoid microspheres - and Liposomes...   
                                    can be experimental systems      
Coacervates - droplets that form spontaneously from charged polymers (1-100ϥm dia) possess osmotic properties, and are surrounded by a tough skin of water molecules consisting of a film of bound water molecules and held together by hydrophobic forces. Allows absorption of of simple molecules from medium; maybe a trapped enzyme.
     Properties of coacervates:            figure*
  • Extremely common; easily form complexes
  • The bound water molecules provide a boundary which separates chemicals
    from the surrounding dilute medium.
  • They "sweep up" chemicals from the surrounding medium. e.g. in a solution of
    1 part gelatin to 10,000 water 95% of the gelatin protein was in coacervates
  • Rather transient especially in acidic or alkaline media                                                 ◊
Proteinoid microspheres - water filled vesicles surrounded by protein boundary
if a dry mixture of amino acids is heated to 130-180o C they polymerize;
if they are then cooled in water they form small spheres about 2 ϥm in dia.
     Properties of proteinoid microspheres:
  • they are 1 to 2 µm in diameter (about same size as coccid bacteria)
  • very stable
  • have an osmotically active boundary which can be seen as a double layer
  • if made of acidic amino acids they stain Gram negative;
    if they have at least 35% basic amino acids they stain Gram positive
  • they can be induced to constrict and "bud"                                                                ◊      
Liposomes* - vesicles surrounded by lipid bilayers              picture*
phospholipid spheres. These are spheres made up of amphipathic molecules (have both hydrophilic and hydrophobic regions). In the presence of both a water and an air phase the form a boundary that has the characteristic structure of a cell membrane
     Properties of liposomes:
  • They aggregate molecules with in themselves and are selectively permeable
  • They can spontaneously increase in mass and complexity
  • If proteins are incorporated into the phospholipid boundary they behave like a selective plasma membrane
  • in 2003 M. Hanczyc, S. Fujikawa, & J. Szostak made liposome that grow & divide via clay
     (reproduce?) and if RNA present it was encapsulated [ a plausible route to 1st cells ?] 
Protobiont*   - a liposome with encapsulated catalytic activity
 

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