A Possible Mechanism For Emergence Of Protocells: Compartmentalizations And Divisions Without Membranes
All life consists of "non-living" molecules. Then what makes them lifelike? In particular, how three basic properties -- reproduction, heredity, and compartmentalization emerge from chemical soup and are integrated to provide a primitive form of a cell? From simple stochastic simulations of two molecule species that mutually catalyze their replication, we found that a compartment of molecules is formed without any membrane, and its growth and division are repeated without any complicated mechanism, as long as the timescale of synthesis and degradation of one molecule species is much slower than the other. The molecule with the slower rate has a single copy in this protocell, and its replication triggers the division events of the protocol -- It plays the role of heredity carriers as DNA or RNA. The mechanism of compartmentalization and division is understood by the synergy between
the discreteness in this molecule number and crowdedness of the other molecule species -- A novel concept in chemical reaction dynamics gives substantial insight to the origin of life.
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LQ12383
Optimal Freezing
One normally thinks of ice as a solid barrier through which nothing can flow,
but such is not the case in the Arctic Ocean. When salty sea water freezes, a
porous mush of ice crystals (much like a sponge) results through which cold, salty
and hence heavy, water drains. A remarkable feature is that sea ice naturally
forms it’s own drainpipes to speed up the drainage by focusing the flow through
the ice; rather like a river network. In this paper1, we uncover an organizing
principle suggesting that nature seeks out and finds the pattern of drainpipes
that most efficiently drains salt into the underlying ocean. This allows us to
predict the dynamics of a wide range of solidifying systems, from salt drainage
out of Arctic ice which drives ocean thermohaline circulation, to controlling
structural defects when manufacturing aircraft engine turbines.
