26. Origin of Life on Earth
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       Coacervate Drops and "Protobionts"

Oparin in Russia has had similar goals to Fox's, namely, to see how isolated and bounded regions of a solution could arise naturally, as potential centers for the development of life.

If a concentrated solution of polypeptides, nucleic acids, polysaccharides, or almost any polymer is gently shaken, it will separate into two phases of different polymer concentrations. Concentrated droplets will form in a more dilute solution.

These coacervate drops are typically 20 gm (200,000 A) in diameter, and may contain 5% to 50% polymer, depending on how they are formed. They have a skin or membrane around them, which is visible in a microscope.

Coacervate drops, like microspheres, are the result of physico-chemical forces and have no direct connection with life.


If materials of smaller molecular weights are added to a solution of coacervate drops, they will distribute themselves unequally between drops and bulk solution, depending on their relative solubilities in the two polymer phases.

Coacervates tend to concentrate some molecules in their interior, an ability that the most rudimentary of protocells would need.

This behavior of coacervates shows how early protocells could have achieved internal compositions that were different from their surroundings, and could have developed a certain amount of chemical independence.

  Page 27 of 36 Glossary